How to Build a Rain Garden

8/7/2019 How to Build a Rain Garden

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A STEP-BY-STEP GUIDE TO

LandscapingFORClean WaterANDHealthy Streams

THE OREGON

Ran Grden Guid


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The Oregon Rain Garden Guide: Landscaping or Clean Water and Healthy Streams2

The Oregon Rain Garden Guide:Landscaping or Clean Water and Healthy Streams

Text by Robert Emanuel and Derek Godwin, Oregon Sea Grant Extension, Oregon State University (OSU);and Candace Stoughton, East Multnomah Soil and Water Conservation District.

Sample rain garden layouts by Heidi Brill. Plant list compiled and edited by Teresa Huntsinger, Oregon Environmenta

Council. Other signicant contributors include Angela Boudro, Jackson Soil and Water Conservation District; Linda

McMahan, OSU Extension Service, Yamhill County; Joy Jones, OSU Extension Service, Tillamook County; and Neil

Bell, OSU Extension Service, Marion County. Editing by Rick Cooper, graphic design by Patricia Andersson, Oregon Sea

Grant, OSU.

Cover artwork: Rain Garden painted by John C. Pitcher Good Nature Publishing 2009.

www.goodnaturepublishing.com 800-631-3086

This project has been unded in part by the United States Environmental Protection Agency under assistance agree-

ment CP-0045105 to the Oregon Department o Environmental Quality. The contents o this document do notnecessarily refect the views and policies o the Environmental Protection Agency, nor does mention o trade names

or commercial products constitute endorsement or recommendation or use.

Many thanks to those who reviewed this document, plant lists, and sample planting designs or accuracy and appro-

priateness. Special thanks to those who made contributions o photos or text.

2010 by Oregon State University. This publication may be photocopied or reprinted in its entirety or noncom-

mercial purposes. To order additional copies o this publication, call 541-737-4849. This publication is available in an

accessible ormat on our Web site at http://seagrant.oregonstate.edu/sgpubs/onlinepubs.html

For a complete list o Oregon Sea Grant publications, visit http://seagrant.oregonstate.edu/sgpubs

This report was prepared by Oregon Sea Grant under award number NA06OAR4170010 (project number E/BET-02-

PD) rom the National Oceanic and Atmospheric Administrations National Sea Grant College Program, U.S. Depart-

ment o Commerce, and by appropriations made by the Oregon State legislature. The statements, ndings, conclu-

sions, and recommendations are those o the authors and do not necessarily refect the views o these unders.

Oregon Sea Grant, Corvallis, Oregon ORESU-H-10-001

The production o this guide was part o Stormwater Solutions,a collective public education eort involving several partners.

Partners responsible or the production o this guide include

the ollowing:


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The Oregon Rain Garden Guide: Landscaping or Clean Water and Healthy Streams

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

The purpose o this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

What is a rain garden? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Why build a rain garden? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Building a Rain Garden: A Step-by-Step Approach . . . . . . . . . . . . . . . . . . . . 6

STEP 1:Observe and map your site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Determine how much area the rain garden will treat. . . . . . . . . . . . . . . . . 6

STEP 2:Determine the location o the rain garden . . . . . . . . . . . . . . . . . . . 6Go with the fow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Respect the fow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Divert the fow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Regulations, permits, and design modications . . . . . . . . . . . . . . . . . . . . 8

Measure the slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

STEP3:Assess soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Testing inltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Determining soil texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Interpreting the inltration test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

STEP 4:Determine the size o the rain garden . . . . . . . . . . . . . . . . . . . . . . . 11Rain garden depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Dig saely! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Delineate the rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Getting water to the rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

D isco nnec t ing do w nspo uts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5

Designing or overfow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Keys to success . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

STEP 5: Constructing a rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Excavating, grading, and berms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Grading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Plumbing the rain garden. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

To amend or not to amend? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

STEP 6:Choose the right plant or the right place . . . . . . . . . . . . . . . . . 20Planting zones and plant selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Compost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Key plant characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Planting tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

A note about invasive species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Mulching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Watering a rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

STEP 7:Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Weeding, pruning, and mulching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Dont drown your plants! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

A note about Oregons regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Sample Rain Garden Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Rain Garden Plant List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

For more inormation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43


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Introduction

Figure 1: Cross-section o atypical rain garden.

(Graphic by East Multnomah Soil

and Water Conservation District

[EMSWCD])

The purpose o this guide

The Oregon Rain Garden Guide was written to helpOregonians learn how to design and build rain gar-

dens to treat the stormwater runo rom their ownhomes or businesses. Rain gardens are gardens

with a purpose; they help reduce the amount o ex-

cess water and associated pollutants reaching local

lakes, streams, and bays. Ultimately this results in

healthier waterways, sh, other wildlie, and people.

This how-to guide provides inormation specic

to Oregons conditions, including the rainall and

appropriate plants or your site. You dont have to

be a stormwater, garden, or landscape proessional

to use this guide. It provides the necessary inor-

mation to saely build and maintain a rain garden,

along with reerences or more detailed guidance

or special conditions. You may also contact the

authors and partners directly or more inormation.

What is a rain garden?

A rain garden is a sunken, generally fat-bottomed

garden bed that collects and treats stormwater

runo rom rootops, driveways, sidewalks, parkinglots, and streets. Rain gardens help mimic natural

orest, meadow, or prairie conditions by inltrat-

ing stormwater rom hard suraces. A variety o

planting plans are included in this manual or your

reerence.

Rain gardens keep our watersheds healthy by

reducing fooding by absorbing rain water rom

hard suraces

ltering oil, grease, and toxic materials beore

they can pollute streams, lakes, and bays

recharging groundwater aquiers by allowing

water to soak into the ground

providing benecial wildlie habitat

RAIN GARDEN DICTIONARY:

Impervious suraces are areas that do not allow rain or snowmelt to inltrate or soak into the soilbelow the surace (or example, roos, driveways, roads, sidewalks, and patios). Some ground areas

that have been severely compacted rom heavy equipment or oot trac may also be considered

impervious i most o the water runs o the surace when it rains.


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Why build a rain garden?

When the Pacic Northwest was covered with

orests and prairies, rainall slowly dripped through

branches and vegetation, seeped through du,and sank into the ground as it slowly percolated to

nearby water bodies. As parts o our landscapes

became more developed, the rainall that lands on

hard suraces was routed into pipes, ditches, and

storm drains. Much o that runo is routed directly

to streams or into the sewer system. The result?

Too much water fowing in a short amount o

time, carrying pollutants that negatively aect the

health o our streams, lakes, and estuaries. Today,

managing stormwater runo by inltrating it into

the ground is one o the simplest ways to actively

protect our streams. Rain gardens help us restore

the natural water cycle in the landscape, which is

critical to ensure healthy streams in both small

towns and large cities.

Do rain gardens attract or breedmosquitoes?

No. For reproduction, mosquito larvae require

a number o days in standing water. Most

urban mosquitoes breed in places like junk

piles where there are old tires or tin cans. In awell-designed rain garden, water is rarely stand-

ing long enough or mosquito reproduction.

Ideally, a rain garden should drain so that water

wont be standing in it or more than 48 hours.

For more inormation, see Mosquitoes at

entomology.oregonstate.edu/urbanent/.

Figure 2 (top): A newly installed rain garden in

Tillamook County, Oregon.Figure 3 (middle): An established rain garden inPortland, Oregon (by Blossom Earthworks).

Figure 4 (bottom): Streams in the Pacic Northwestare normally buered rom pollution and sudden

fashes o water by their surrounding orests and

grasslands. In an urban environment, water rom

roos and streets is oten piped directly into streams,

delivering pulses o polluted, damaging water and

sometimes causing localized fooding.


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HORIZONTAL DISTANCE(233)

LINE LEVEL

STAKE

RISE(18) STAKE

Regulations, permits, and designmodications

Some cities and counties have specic regulations

regarding disconnecting downspouts, routing or

piping water o-site, and setbacks to structures,

steep slopes, and property lines. They may also

require a permit. Always check with your citys

building or planning department i you live within

city limits; otherwise, check with your county

government.

Rain gardens may be designed with impermeable

liners, rock trenches, and piping to saely route

water away rom structures and o-site. These de-

signs would allow you to build rain gardens closerto structures, on steep slopes, in soils that dont

drain well, and in other challenging situations.

However, these designs are beyond the scope

o this guide. We recommend that you contact a

licensed landscape proessional or engineer or

assistance with these alternative designs.

Measure the slope

Tools needed:

Two stakes

Survey line or string

Line level

Measuring tape

Calculator

Steps:Measure and calculate the slope o the site to as-

sess how water will be routed to and rom your rain

garden. It is critical to make sure your property has

a slope o less than 10 percent beore constructing

a rain garden there.1. Place stakes in the ground at the top and bottom

o the slope to be calculated.

2. Attach a survey line (or any heavy-duty string) to

the two stakes. Be sure that the line touches the

ground on the uphill stake. Use the level to make

sure the line is level.

3. Measure the horizontal distance (along the line)

between the two stakes.

4. Measure the rise (vertical distance) rom the

ground up to the line on the downhill stake.

5. Calculate the slope by plugging your numbers

into the ollowing ormula:

Note: both measurements must use the sameincrements (or example, inches).

slope =RISE

HORIZONTAL DISTANCEx 100%

18"

Example:RISE = 18"

HORIZONTAL DISTANCE = 233"

x 100%233"

7.7 % =

Graphic:EMSWCD


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STEP 3: Assess soil

The ability o soil to drain water is one o the most

important considerations or understanding the

site and properly sizing a rain garden. An inltration

and texture test will help you determine the soils

capacity to absorb and percolate water down into

the lower layers.

Testing inltration

1. Dig a test hole in the area where the rain garden

will be built. Try to site the hole in the middle o

the planned rain garden. Dig a hole to the expect-

ed depth o the rain garden (rom grade to the top

o the rain gardens base). Note that ideally, this

test should be done when soils are not rozen andwhen groundwater levels may be highest, such as

in the spring.

2. Fill the hole with water to just below the rim. This

should be the same depth o water expected i the

rain garden lled to the rim. Record the exact time

you stop lling the hole and the time it takes to

drain completely.

3. Rell the hole again and repeat step 2 two more

times. The third test will give you the best mea-

sure o how quickly your soil absorbs water when

it is ully saturated, as it would be during a rainyperiod o the year or during a series o storms

that deliver a lot o rainall in a short period o

time. Building a rain garden to handle these

conditions is a way to be sure you will not cause

damage to your own or a neighbors property.

4. Divide the distance that the water dropped by the

amount o time it took or it to drop. For example,

i the water dropped 6 inches in 12 hours, then 6

divided by 12 equals 1/2 inch per hour o inltra-

tion. I the slowest inltration rate measured o

the three trials is less than 1/2 inch per hour, then

you should dig another 3 to 6 inches deeper and

repeat the above steps. Repeat this process at

various depths down to 2 eet, or until you have at

least 1/2 inch per hour inltration.

!Note: Soils with drainage o less than 1/2 inch perhour are not appropriate or rain gardens with-

out signicant modications in design. Consult

a licensed landscape proessional or engineer or

assistance in these circumstances.

1

2

3


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Determining soil texture

1. Take a handul o the soil you have excavated

rom your inltration test. Pulverize it in yourhand and remove any bits o organic matter or

obvious rocks.

2. Wet it with a small amount o water and rub it

between your thumb and index nger. Dont

saturate it until it is runny mud. You might eel

stickiness, grittiness, or smoothness. The grittier

the eel, the more sand is present in your soil.

The slicker the soil, the more clay in it. Smooth

soils are sometimes an indicator o a ne silt or

loam. Discard the soil.

3. Next, take another sample in your hand. Wet it

until it has the consistency o dough. You should

be able to orm a ball that holds together with

the soil in your palm. I you cannot get the ball to

orm, then your soil is very sandy. In most soils,

however, you should be able to create a rough

ball.

4. Knead the soil together between your thumb and

ngers and attempt to orm a ribbon. As you

build the ribbon, it will either hold together or

break o. I the soil breaks quickly in the process,

then it likely has a high sand content. I the rib-

bon orms quickly and stays strong, it has moreclay.

I the soil orms a ribbon less than 1 inch in

length beore it breaks, the soil is sandy or silty.

I the soil makes a ribbon 1 to 2 inches in length

beore it breaks, the soil is clayey.

I the soil makes a ribbon greater than 2 inches

beore it breaks, it may not be suitable or a rain

garden constructed without proessional help,

depending on how ast the soil drains during the

inltration test.

Figure 7a: Conducting a soil eel test by making a ball with the moistened soil, tosee how easily it alls apart as well as what texture it has (sticky, silky, or gritty).(Photo: Gina Emanuel)

Figure 7b: Using a soil ribbon to test soil or clay, loam, or sand content. Thelonger and rmer the ribbon, the more clay content in the soil. (Photo: Gina Emanuel)


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The Oregon Rain Garden Guide: Landscaping or Clean Water and Healthy Streams 1

Interpreting the inltration test

Building a better soil

Amending with compost is recommended to

improve initial plant and microbial health. I

your soil has high clay content, soil amend-

ments may be needed to improve conditions

or good plant health. Sites with very high clay

content and low drainage are usually inappro-

priate or the types o rain gardens described

in this guide, without signicantly altering the

design or better drainage (such as adding

subsurace drain pipes and drain rock).

I you plan to amend the soil, a typical soilmixture contains 20 to 40 percent organic

material (compost); 30 to 50 percent clean,

coarse sand; and 20 to 30 percent top soil.

Note: do not add sand to a highly clayey soil.Soils are commonly amended to a depth o

1824 inches.

STEP 4: Determine the sizeo the rain garden

Always check with your local planning department,

public works, or stormwater utility beore design-

ing your rain garden. I your local jurisdiction does

not have a recommended size calculation or a

rain garden, then we recommend the size o the

rain garden be at least 10 percent o the impervi-ous surace draining to the garden. Rain gardens

should ideally be between 6 and 24 inches deep.

To use this number, your soil should drain at least

1/2 inch per hour or greater. Compare the result o

your soil inltration test with the table above, ora good idea o how your soil infuences the size o

the rain garden. Rain gardens o 10 percent and 1/2

inch minimum inltration rate should treat a large

majority o storms in Oregon.

Using the area o impervious surace that you

calculated in Step 1, multiply this by 0.10 (or 10

percent). The result will be the area o the rain

garden in square eet. The calculation is:

Drainage rate Recommendation

Less than 1/2 inch per hour Do not build a rain garden on this site without proessional

assistance.

Between 1/2 and 1 inch/hourLow inltration or a rain garden. Homeowners may want to build

a larger or deeper garden, or likewise plan or additional overfow

during high-rainall storms.

Between 1 and 1 1/2 inches/hourAdequate inltration or a rain garden. Plan or sucient overfow

during high-rainall storms.

Between 1 1/2 and 2 inches/hour Adequate inltration or a rain garden. Plan or sucient overfowduring high-rainall storms.

Faster than 2 inches/hour

High inltration or a rain garden. Design should eature ewer

moisture-loving and more drought-tolerant plants. The rain garden

may also be sized to hold smaller amounts o water, have a deeper

mulch layer, or have denser plantings.


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(Length o surace area x Width o surace area)x .10 = total rain garden area

An example: 30 eet x 12 eet = 360 square eet

x .10 = 36 square eet o rain garden

The more impervious area you want to treat, the

bigger your garden. The size o your rain garden

will also depend on the space available and your

budget. I you dont have enough space, you can

build multiple rain gardens or build a smaller one

and plan or it to overfow more oten.

Note: Rain gardens should be a minimum o veeet wide to accommodate gentle side slopes that

will host plants and minimize soil erosion.

Rain garden depth

Most rain gardens should be between 6 and 24

inches in ponding depth with 24 inches o ad-

ditional depth or saety. This means that rain

gardens range rom 8 to 28 inches in depth. The

table below is a general guide or rain garden pond-

ing depths based on dierent drainage rates. Add

depth where overall size is restricted by setbacks,

structures, vegetation, or other obstacles.

Drainage rate Suggested rain garden ponding depth

Between 1/2 and 1 inch/hour 1224 inches

Between 1 and 2 inches/hour 68 inches

Faster than 2 inches/hour 6 inches

Typical ponding depth624 inches

Figure 8: Pondingsurface is denoted

by the doed line.

(Graphic: EMSWCD)

Note: remember to account or the addition omulch when you plan or your nished depth (see

Mulching on page 23). For example, i you areadding 3 inches o mulch to your nal planted gar-

den and it needs to be at least 12 inches deep, you

must excavate to a depth o 15 inches rom grade.


Thesizeo a rain gardenreers to the volumeo water it can hold beore the water overfows

at the exit point. This volume is described in

terms o ponding depth and square eet o

surace area (depth x width x length).Ponding depth is the depth at which the watercan pond beore it fows out o the rain garden

(see Figure 8). It is measured rom the surace

o the rain garden at its lowest point to the

elevation o the outlet. Rain gardens gener-

ally should range between 6 and 24 inches

in ponding depth, adding 24 inches o extra

depth below the outfow or saety.


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Dig saely!

Its the law in the state o Oregon to call the Utility

Notication Center by dialing 811 or 1-800-332-2344

beore beginning any excavation. The service is

ree and convenient or homeowners, contractors,

excavators, landscapers, etc. Anyone planning to

dig must contact the Center at least two businessdays prior to digging, in order or the undergroundutilities to be located and accurately marked using

color-coded paint. For more inormation on

digging saely, visit the OUNC Web site:

www.digsaelyoregon.com.

Delineate the rain garden

Use a garden hose, string, stakes, or marking paintto delineate the boundary o the rain garden on the

site. Beore you dig, be sure to note any existing

utilities or vegetation that might be damaged by

digging (see note above).

Getting water to the rain garden

Your garden will not actually be managing storm-

water i it does not collect rain water rom your

homes impervious suraces. That means you

must nd ways to get water rom your collection

points to your garden, sometimes by diggingtrenches, running gutter extenders, or even build-

ing articial streams that run only when the rain

alls. The water may be routed using a pipe, rock

tiles, or other hard suraces, or a small swale (ditch)

lined with rock (3/4-inch diameter, washed drain

rock or pea-sized gravel). I using a pipe, we recom-

mend a 4-inch diameter ABS.

I not using a rock-lined trench, the outlet o the

routed water and inlet o the rain garden should be

lined with rock (again, 3/4-inch diameter, washed

drain rock or pea-sized gravel) to prevent erosion.In addition, a 4-inch-wide strip o grass could be

used to lter and settle sediment rom your rain

water beore it enters the rain garden.

Figures 9a and b: Delineating rain garden boundaries with a garden hose (top)and marking paint (above). (Photos by Robert Emanuel, OSU)

Figure 10: Moving water rom a gutter to a gardencan be as simple as a piece o buried 4-inch drain pipe.

Note that the pipe is buried at least 12 below the

surace as required by Oregons plumbing code. See

note on page 19. Photo:PortlandBureauoEnvironment

alServices


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Figure 13 (right): A dry stream bed conveys water across a surace beore itenters a rain garden. (Photo: Judy Scott, OSU)

Figure 11: Using a rock-lined trench to convey water across a walkway (Photo: Portland Bureau o Environmental Services [BES])

Figure 12: Trench drain through a sidewalk at a building in Portland.(Photo: Derek Godwin, OSU)


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Disconnecting downspouts

Disconnecting downspouts is an important part

o rain garden construction. Avoid creating saety

and structural problems when disconnecting any

downspouts rom your storm sewer by ollowing

these saety guidelines:

Dont disconnect a downspout in an area that

is too small to drain the water properly.

Disconnected downspouts must be extended

to discharge water at least 6 eet rom a struc-

ture with a basement or 2 eet rom a crawl

space or slab oundation.

Direct water away rom your structure, a retain-

ing wall (by at least 10 eet), a septic drain eld,

or an underground storage tank.

The end o the downspout extension must be

at least 5 eet away rom a neighboring property

and 3 eet rom a public sidewalk. Do not direct

water toward a neighboring property, especially

on a steep slope.

Steps or disconnecting:

1. Measure the existing downspout rom the top

o the standpipe, and mark it at least 9 inches

above the standpipe. A standpipe is the pipeleading into the below-ground storm sewer.

2. Cut the existing downspout with a hacksaw at

the mark. Remove the cut piece.

3. Plug or cap the standpipe. Do not use concrete

or another permanent sealant.

4. Attach an elbow to the newly cut downspout by

inserting the elbow over the downspout. Then

use at least two sheet-metal screws to secure

the two pieces.

5. Measure and cut the downspout extension sothat when it is attached, you will be ollowing

the saety guideline above. Fit the extension

over the elbow and attach it with sheet-metal

screws.

6. I the extension does not connect directly to a

below-ground pipe or lead into a rain garden,

use a splash block or gravel to prevent soil

erosion.

7. Remember that each section should unnel into

the one below it. All parts should be securely

astened together with sheet-metal screws.

Be sure to maintain your gutter system. Inspect

it regularly or leaks, sagging, holes, or other

problems. It is a good idea to annually inspect

and clear debris rom gutters, elbows, and other

connections beore the rains arrive.

This material is condensed rom How to Manage

Stormwater: Downspout Disconnection, City o

Portland Bureau o Environmental Services

publication BS 07011. It is used here with permission

o the City o Portland, BES. The ull document can

be ound at www.portlandonline.com/bes/index.

cm?c=46962&a=188637.

Figure 14. Downspout connected to downspoutextension that directs fow away rom a buildings

oundation. Note sheet-metal screws.(Photo: Robert Emanuel, OSU)


16/44


Designing or overfow

When properly sized, a rain garden is designed

to handle roughly 8090 percent o the water

that alls on a given impervious surace. There-ore, extreme events should be considered when

designing your garden. For this reason, it is critical

to include plans or overfow. This should be a

notch or a pipe in the berm, at least 2 inches lower

than the berm. The overfow could lead to one o

several options:

a fat area in your home landscape where water

can be saely absorbed,

another rain garden,

a French drain or rock-lled soakage trench,

a swale or drainage ditch, or

return stormwater to its original destination be-

ore the rain garden was built (such as a public

sewer, street gutter, storm drain, or pipes and

catch basin).

Be sure to discuss your plans or overfow with

your local planning department. They typically

have specic, approved locations or draining the

overfow o-site. They may also require a permit

or a rain garden.

Figure 15: Curb-cut inlet or a parking lot and an overfow device (pipe andscreen) or a parking lot in Gresham, Oregon. (Photo: Derek Godwin, OSU)

Figure 16: PVC pipe outfow rom a coastal Oregon rain garden. The rocks,mulch, and gravel help protect the area rom erosion. (Photo: Robert Emanuel, OSU)

Figure 17: A rain garden in Gresham, Oregon, llswith rain. Note the use o rocks at the outfow point

near top. (Photo: City o Gresham)


17/44


Note: For smaller gardens, or gardens in high rain-all areas with soils with low inltration rates, you

will need to take extra care in routing the overfow

away rom the garden in a sae manner.

Keys to success

Permits and design modifcations:Check with your local government (city or county

planning department) to

nd out whether you can legally build a rain

garden (and whether you need a permit)

get inormation on disconnecting downspouts

or routing water o the site

learn about any design requirements or setbacks

You may decide that you need the help o a licensed

landscape proessional or engineer.

Be kind to trees:Its a good idea to avoid placing a rain garden

beneath the drip line o large trees. The tree roots

will be damaged by the excavation and may also be

overwhelmed by the amount o water that pools

beneath them.

When is the best time to build?

The ollowing schedule is recommended to pre-vent soil compaction, maintain the soils ability to

inltrate stormwater, and minimize the need or

watering the plants:

Conduct site assessments and design the gar-

den in the all, winter, and spring when the soil is

wet but not rozen;

Excavate and build the garden when the soil is

dry enough to work with easily; and

Plant vegetation in the all and as early as pos-

sible the ollowing spring.

STEP 5: Constructing a rain garden

Excavation, grading, and berms

Plan to place the spoils to the outside edge o thegarden and away rom the infow point. Use the

spoils and any excess soil amendments to orm

the berm that bounds the rain garden on one

or more sides, depending on the terrain. Berms

should be built to have at least 2 inches o height

above the elevation o the outlet.

Whether digging by hand or machine, excavate

the soil rom the outer edge o the rain garden to

minimize soil compaction.

We recommend that the slope on the rain gardenberm be at least 18 inches o horizontal length to

6 inches o vertical height (3:1) or fatter on both

sides o the berm. I the rain garden is 12 inches in

depth, you will need to have 36 inches o slope on

either side o the berm.

Figure 18: Excavator is located outside o the rain garden in orderto make sure the machine does not compact soil in the rain garden.(Photo: Robert Emanuel, OSU)


18/44


19/44


Note: Oregon State Plumbing Code requires thatany buried utility pipe should be at least 12 below

the soil level starting at the downspout. It also

requires underground plumbing to be a durablematerial such as Schedule 40 ABS or PVC. While

corrugated plastic pipes are requently ound in

rain gardens (including some photographed in this

guide), these materials may not last, especially in

colder climates. I using an infow pipe buried 12

inches deep, a rain gardens nished depth will

need to be between 14 and 18 inches.

To amend or not to amend?

Rain gardens depend on healthy plants and soils

to capture, clean, and lter the stormwater runo.

As mentioned in Step 1, your soils may need to

be amended to ensure strong plant survival and

microbial health. Where possible, your existing soil

should be tilled to 18 to 24 inches deep i amend-

ing with compost, topsoil, or sand. See note on

page 20.

Figure 24: An outfow notch in a Portland, Oregon, rain garden, protected byrock to prevent soil erosion. (Photo: Robert Emanuel, OSU)

Figure 22: Four-inch ABS pipes here will convey waterrom this building into a rain garden. Pipes like these

must be graded to drop about 1 inch or every 10 eet

so water fows away rom the building but does not

build up too much velocity by the time is arrives in the

rain garden. (Photo: Robert Emanuel, OSU)

Figure 23: The point where water enters a rain garden should be well armoredwith rock and plants (beach strawberries here) to prevent erosion.(Photo: Robert Emanuel, OSU)


20/44


STEP 6: Choose the right plantor the right place

Fertilizers and pesticides oten contribute to storm-water pollution in streams and lakes. Since rain

gardens are designed to treat stormwater runo, it

is very important to choose plants that can survive

and thrive without chemical inputs. It is also good

practice to choose plants and design your garden to

require minimal to no extra water.

Planting zones and plant selection

Plants vary in their tolerance o certain conditions,

such as shade, fooding, moisture, and cold tem-

peratures, while maintaining their ability to surviveand grow. Rain gardens have zones that vary in

wet and dry conditions and possibly sunlight and

shade; thereore, plants need to be selected based

on their tolerance to these conditions and placed

in the corresponding zone to survive and thrive.

Furthermore, plants need to be chosen based on

their ability to survive in the climate relative to the

region in Oregon in which they are planted (that is,

Willamette Valley, coast, southwest, central, and

east). Rain gardens are generally meant to be low

maintenance.

Compost

Compost helps the soil hold moisture, increase

microbial activity, improve its ability to lter and

adsorb pollutants, and increase plant survival in therst ew years as it slowly biodegrades. Be sure to

use weed-ree mixes.

!Note: Rain garden plants do not have to be wet-land or water plants. In act, they should be able to

tolerate drying out or long periods with little to no

supplemental irrigation, depending on where you

live in Oregon and how long the plants have been

established.

Rain gardens can be divided into three zones, rela-tive to their wet and dry conditions: moist, moderate

and dry. I you select plants rom the lists provided in

this guide, be sure to pay attention to their designa-

tion as tolerant o moist, moderate, and dry

soil conditions. Use plants that are designated as

doing best in moderate and dry conditions only

on the slopes or otherwise dry parts o the garden.

Do not put a plant that cannot tolerate wet eet in

the bottom or wettest part o your garden, because it

could drown during rainy periods.

Soil type will also infuence the plants and the sizeo dierent moisture zones. For example, rain gar-

dens built in high-clay or slow-draining soils should

be planted with more plants that tolerate wet

eet, while rain gardens in sandy or ast-draining

soil can be planted with more dry-adapted plants

(listed here with moderate or dry designations)

In ast-draining rain gardens, group your moisture-

loving plants within a ew eet o the infow points.

Figure 25: Rock, gravel, and sedges protect the infow point in a rain garden.(Photo: Chris LaBelle, OSU)


Zones o wet and dry conditions

Moist: plant preers moist soil and toleratesdry soil other times o the year.

Moderate: plant can tolerate moist and drysoils equally.

Dry: plant tolerates and even thrives in drysoil during most o the year.


21/44


Filling up the rain garden and watching it drain

several times will help you visualize where water

pools and where it drains quickly. This will help

you choose the right plant or the right place.

Visit local examples o rain gardens to get ideas

o what plants thrive and how the design works

in your local area.

Because this guide was written with most o Or-

egon in mind, we recommend that gardeners use

the lists and designs provided here as suggestions,

not as ironclad rules to ollow. Be creative, and be

prepared to experiment with the garden; garden

areas and conditions are always variable, and no

design is ail-sae.

Remember that plants can do some o the work

to make a rain garden easier to maintain. Some

especially tough plants, such as sedges or bunch

grasses, should be grouped around eatures likeinfow and outfow points, to slow down water

as it enters the rain garden. Use groundcovers

on berms and other areas where erosion is a

concern. Several designs are suggested on pages

2835.

!The area around your infow will retain the most

moisture in your rain garden, meaning that what

you plant there must be the most tolerant o moist

soil.

Figure 26: Planting zones refect the areas where the garden will have the most and least water when fooded, aswell as during the dry season. The graphic on the let illustrates the topographic zones o the rain garden, the

graphic on the right illustrates zones o high and low soil moisture during the dry season. (Graphic: Robert Emanuel, OSU)

Figure 27: Planting zonesin this cross section illustrate

where soil will be moist

during the wet season.(Graphic: EMSWCD)


22/44


Key plant characteristics

Other plant characteristics and plant selectionWhile rain gardeners should ocus on selecting

and placing plants that may tolerate more or lesswater, there are other characteristics to note.

Remember, rain gardens can and should be attrac-

tive eatures in your landscape, rather than just

places to treat stormwater. Other characteristics to

consider include:

What is the plants height and width?

Does the plant have attractive oliage, fowers, or

ruit?

Does it attract benecial insects and wildlie?

Does it look good with neighboring plants andlandscape?

Seasonality

Shade tolerance

Temperature requirements

! Remember that plants grow! This simple act

should keep you rom overplanting your rain gar-

den or placing plants too close together. Respect

their ultimate size requirements and keep in mind

that these vary throughout Oregon.

Planting tips

When planting, be sure to dig a planting hole at

least as big as the pot, i the soil has been amend-

ed. I you are planting into unamended soil, dig

a hole that is at least twice the diameter but the

same depth as the pot. Most native and nonna-

tive plants need to be planted at the same depth

as they were growing in their pots. Leave some

compost and soil mixture mounded at the bottom,

as appropriate, to keep your plant at the same level

as it was in its original container.

Careully remove the plant rom its container. I the

plant roots have ormed a solid mass around the

outside o the pot, gently loosen them or careully

score the outside layer with a sharp knie. Lower the

root ball into the planting hole slowly, to prevent

cracking or breaking o the soil around the roots.

I the root ball was opened up, spread some o the

roots over the mound in the center o your hole.

Backll your hole with well-drained soil rich in

compost, being careul to make sure you do not

cover the crown o the plant i it was exposed in

the original container. Be sure to rm the soilaround the plant and water well with a slow stream

o water or soaker attachment.

A note aboutinvasive species

Invasive plants such as

English Ivy, Japanese

knotweed, spurge laurel,

or butterfy bush cost Oregonians millions

o dollars in control, prevention, and directeconomic losses. An invasive plant is one that

escapes cultivation and multiplies in other

habitats, to the near exclusion o species that

would occur naturally.

Gardens and gardeners are among the most

important pathways or invasive plants to

move into new places. You can help stop

the biological invasion by eliminating known

invasive plants rom your garden; preventing

the introduction o new, aggressive plants;

and replacing nonnative invaders with riendlynative plants in your landscape.

For common invasive plants to avoid as well

as some excellent alternatives, consult the

publication GardenSmart Oregon, available at

www.oregoninvasivespecieshotline.org and

through your local Soil and Water Conserva-

tion District or OSU Extension Service oce.


23/44


Mulching

Mulch is another important part o the rain

garden. It will help shade the soil and keep it cool

and may increase soil moisture during the drysummer and all months. The right mulch can also

help control weeds. More importantly, microbial

activity in the mulch helps to break down some

o the common pollutants in stormwater. For this

reason, we recommend always applying mulch to

new rain gardens and maintaining some mulch in

established ones.

Double-shredded conier bark mulch (also known as

bark dust) is probably the most commonly used

in landscape plantings in the Pacic Northwest.

Douglas-r and hemlock are the most commonly

sold barks, although pine bark is also available. Bark

mulch is available in a range o grades, rom ne

through medium to large bark nuggets. We recom-

mend using ne-grade bark mulch rather than nug-

gets, as the latter will foat. We do not recommend

using sawdust or grass clippings, as these materials

will alter your soil chemistry and can aect the abil-

ity o the garden to support healthy plants.

Apply mulch at a rate o 23 inches evenly across

the rain garden on the edges or slopes o your raingarden. I you choose not to use bark mulch in the

lowest point o the garden, then be sure to apply a

2- to 3-inch depth o compost instead.

Rocks and gravel are oten used at infow and outfow

areas to dissipate energy rom water and prevent

erosion. They will also make maintenance in the rain

garden easier. Rock and gravel are important design

elements that can add interest to the rain garden.

Washed pea gravel is an attractive small-grade rock

or use in the base o the rain garden.

Compost is another alternative or covering the

base o the rain garden. It will not suppress weeds

as well as wood chips or other materials, but it will

succeed in adding ertility to the soil and in lter-

ing pollutants. More nely textured compost is

less likely to foat in heavy rains. Apply compost at

the same rate as indicated in the chart to the right.

How much mulch?

To calculate the total cubic yards o mulch needed

or your rain garden project, ollow these steps:

1. Multiply the length o your rain garden by the

width to nd the square ootage.

2. Multiply that square ootage by 0.25, which will

equate to 3 inches o mulch.

3. Divide that value by 27 to yield cubic yards o

mulch needed or your project.

The steps above can be used to quickly estimate

the necessary amount o mulch to purchase based

on various depths o mulch. Remember not to

pile mulch alongside the stem o plants. Mulch

is moist and can lead to rotting around the stem.Also, remember to break up any mulch that may

be dry or clumped together as you spread it over

your rain garden.

For more inormation on mulches, please consult:

Bell, N., D. M. Sullivan, and T. Cook. 2009. Mulch-

ing Woody Ornamentals with Organic Materials.

EC 1629-E. extension.oregonstate.edu/catalog/pd/

ec/ec1629-e.pd

Cubicyards omulch

Rain garden square eet andmulch coverage based on depth

1 2 3

1 338 sq. t. 158 sq. t. 108 sq. t.

2 676 sq. t. 316 sq. t. 216 sq. t.

3 1,014 sq. t. 474 sq. t. 342 sq. t.

4 1,352 sq. t. 632 sq. t. 432 sq. t.

5 1,690 sq. t. 790 sq. t. 540 sq. t.

6 2,028 sq. t. 948 sq. t. 648 sq. t.

7 2,366 sq. t. 1,106 sq. t. 756 sq. t.

8 2,704 sq. t. 1,264 sq. t. 864 sq. t.

9 3,042 sq. t. 1,422 sq. t. 972 sq. t.

10 3,380 sq. t. 1,580 sq. t. 1,080 sq. t.


24/44


Watering a rain garden

Even ater you have chosen and careully planted

the right plant in the right place and mulched

the garden, it is important to make sure new plantsget sucient water during their rst and possibly

second dry summer season, until they are ully

established. This is especially true i the rain garden

was planted in the spring or summer.

As with any watering regime, water deeply and

slowly during the coolest time o the day (evenings

i possible). Soaker attachments or soaker hoses

are particularly useul or this purpose. Use a soil

probe or stick to check whether moisture is pres-

ent in the rain garden at a depth greater than 23

inches.

Ater the rst or second dry season, depending

upon how good the plants look and how hardy they

are, you may be able to stop watering altogether

and depend on rain entirely. Remember that the

more native plants you use in your rain garden and

landscape, the less supplemental water youll need

to apply during drought periods.

STEP 7: MaintenanceWeeding, pruning, and mulching

You will need to weed your rain garden during the

rst couple o years. Try to get out all the roots o

the weedy plants. Weeds may not be a problem in

the second season, depending on the variety and

tenacity o weeds present. In the third year and

beyond, the grasses, sedges, rushes, shrubs, trees,

and wildfowers will begin to mature and should

out-compete most o the weeds. Weeding isolated

patches might still be necessary on occasion.

Be sure to maintain the rain garden plants in

whatever ashion satises you the mostas a

wild-looking garden, a more manicured space,

or something in between. Plants may need to be

pruned as appropriate or the look you desire in

your garden.

Maintain the organic mulch layer in your rain gar-

den by replenishing it when needed. Apply mulch

Figure 28: A rain garden that is mulched with gravel rather than bark.

(Photo: Portland BES)

Figure 29: Gravel, rocks, and even dritwood add to the interest in this raingarden. The pea gravel also acts as mulch, helping to retain soil moisture while at

the same time minimizing erosion. (Photo: Robert Emanuel, OSU)


25/44


to a 2-inch depth on bare soil. I your rain garden

receives any sediment or soil eroded rom other

locations in your landscape, you may need to cleanthis out on occasion. It is important also to keep

exposed the rocks, tiles, or other hard suraces you

placed in the rain garden to slow water at the infow

and outfow points, so that they can continue to

slow down water and prevent erosion.

Depending upon the local climate and plant choice,

plants may need supplemental water during the

summer. This is especially true in eastern, cen-

tral, and southern Oregon. The use o native and

drought-tolerant plants will help reduce the amount

o supplemental irrigation during dry periods.

Figure 30 (above): A newly established rain garden in Gresham, Oregon (Photo: City o Gresham).

Figure 31 (right): This Willamette Valley rain gardenis planted with Autumn Joy Sedum (Sedum

telephium), slough sedge (Carex obnupta), New

Zealand sedge (Carex testacea), yellow-eyed grass

(Sisyrinchium caliornicum) and mallow (Malva spp.).

(Photo: Chris LaBelle, OSU)


26/44


Dont drown your plants!

Another consideration is to make sure your plants

in the base dont drown in their rst winter. Plants

need air in the soil, so when the rain garden staysconsistently fooded or long, wet winters, it may

become necessary to notch the berm at the outlet

to a lower elevation or add more notches to the

berm. This will help the rain garden drain a little

aster and give the plants a chance to establish

healthy roots. Ater the rst winter, ll in the notch-

es and allow it to unction normally. Some proes-

sionals and gardeners even advocate diverting

stormwater rom the rain garden or the rst year or

two while plants become established, especially in

heavy soils.

A note about Oregons regions

Oregon is a much more geographically diverse stat

than most. Climates and soils can vary signicantly

between the coast, Willamette Valley, Cascades,

eastern high desert, and southwestern mountains.

Below are a ew tips on region-specic items to be

aware o in designing, building, or maintaining a

rain garden.

Willamette Valley:

Most o the materialsincluding many o the plant

selections in this guidewill help rain gardeners

in the Willamette Valley. With its generally mild

seasons, good soils, and mostly fat territory, the

Willamette Valley presents ew obstacles or raingardeners. When planning your rain garden or the

Willamette Valley, keep these things in mind:

Summertime temperatures can occasionally

exceed 90 degrees; thus, some plants in sunny

locations with ast-draining soils will need supple

mental irrigationat least or the rst two or

three years while roots are becoming established

Wintertime temperatures in some locations can

drop well below reezing and thus create prob-

lems or more tender or sensitive plants. It is

important to choose plants adapted to both summer and winter conditions in your area.

The Willamette Valley contains the states bigges

cities, each o which may have their own require-

ments or on-site stormwater management

(and rain gardens). I you live in Salem, Eugene,

Gresham, or Portland, contact your local govern-

ment or more inormation.

Coastal Oregon:

With the infuence o strong Pacic winds, abun-

dant rainall, and generally milder temperatures, thcoast can be challenging or rain gardeners but also

presents some great opportunities. When planning

your rain garden on the coast, keep these things in

mind:

Strong winds can dry out and damage plants any

time o the year, especially or gardens located

near the beach. Provide or shelter, or plan your

plant selections to take account o the wind dam

age. Additional water may be necessary during

Figure 32: A rain garden in Portland, Oregon. (Photo: Portland BES)


27/44


the summer months, when drying winds can be

most damaging or newly established rain garden

plants.

On the Oregon coast, rainall is very abundant.Where coastal soils drain at less than 1 1/2 inches

per hour, size the rain garden to at least 15

percent o the impervious surace. For example,

a rain garden is designed to capture runo rom

a 300-square-oot surace. Hence, the calcula-

tion is 300 x .15 = a 45-square-oot rain garden.

Consult our online materials at extension.

oregonstate.edu/watershed/rain-gardens or

more inormation on using the modeling

method to size your rain garden or your soil

and precipitation.

Some beach homes are built on ossilized sand

dunes. Soils on and around these geologic ea-

tures will drain extremely rapidly, oten in excess

o 2 inches per hour, making a rain garden unnec-

essary or impractical. Furthermore, the additional

water rom a rain garden built on a ossilized

dune may cause it to slump or even collapse. We

do not recommend constructing a rain garden

under these conditions.

Southwestern, central, and easternOregon:

Gardening in southwestern, central, or eastern

Oregon can be rewarding but has its own set o

challenges. These arid and semi-desert regions are

characterized by volcanic, rocky, or clay soils, and

steep slopes. And i that isnt enough, many gar-

deners must balance these restrictions with hungry

deer and the reality o living in a wildre-prone area.

When planning your rain garden or either region,

keep these actors in mind:

I you live in a re-prone area, avoid using plantsin your rain garden that are fammable. Plants

with dry material (such as leaves or needles)

and those with ne structure, aromatic leaves,

loose bark, or resinous sap tend to be fammable.

Consult the Extension publication Fire-ResistantPlants or Oregon Home Landscapes or moreinormation and a list o re-resistant plants

(available online at extension.oregonstate.edu/

emergency/FireResPlants.pd or by visiting your

local OSU Extension Service oce).

These semi-arid regions have long, dry summers

with very little rainall. Depending on your plant

choice, it may be necessary to irrigate your rain

garden two to three times each summer to keep

the plants healthy, attractive, and re-resistant.

I deer plague your garden, use rain garden plants

that are also deer-resistant. Although ew plants

are truly deer-resistant in every situation, mostnurseries can provide a list o plants that deer

tend to avoid.

Central and eastern Oregon winters are longer

and colder than in other areas o Oregon. Plants

may not establish new roots well in rozen soils.

Plan to construct and plant your garden early

enough in the late summer to allow or plants

to become established. Native plants that can

handle the annual swings in temperature will

survive best in a low-care rain garden.

I you live in a location with ast-draining volcanicsoils, you might want to make your rain garden

shallower or smaller, depending on your space

constraints or needs. Consult our online materi-

als at extension.oregonstate.edu/watershed/

rain-gardens or more inormation on using the

modeling method to size your rain garden or

your soil and precipitation.

Figure 33: Rain garden at Astor Elementary Schoolin Portland, OR. (Photo: Candace Stoughton, EMSWCD)


28/44


yr SS

gr

dr

pc

Os

Dr

Ds

cr

Gc

Drlp

CENTRAL OREGON SUN

Abbr. Common name Scientifc name Qty.

SS Smooth sumac Rhus glabra 1Ds Douglas spiraea Spiraea douglasii 3Dr Dwar redtwig dogwood Cornus sericea Kelseyi 11Gc Golden currant Ribes aureum 1Os Oceanspray Holodiscus discolor 1gr Canada goldenrod Solidago canadensis 13cr Common rush Juncus eusus var. pacicus 22dr Dagger-lea rush Juncus ensiolius 13lp Large-lea lupine Lupinus polyphyllus 13pc Purple conefower Echinacea purpurea 6yr Yarrow Achillea milleolium 9

Sample Rain Garden Layouts

These sample rain garden layouts use plants suitable

or the states dierent regions. Consider whether

you want your garden to be ormal, inormal, round

or square. Use these designs to give you ideas or

how to incorporate dierent types o plants into the

wetter and drier zones o your rain garden.

The abbreviations used will help you see at a glance

which type o plant is being reerenced. Two capital

letters denote a tree; a capital and lower-case com-

bination denotes a shrub; and two lower-case letters

mean the plant is a perennial, rush, sedge, or grass.


29/44


NBcr

Dr

Tg

wf

SuBh

th

Dr

Mo

wf

CENTRAL OREGON SHADE


NB Pacic ninebark Physocarpus capitatus 1Bh Black huckleberry Gaylussacia baccata 4Dr Dwar redtwig dogwood Cornus sericea Kelseyi 8Su Gro-low sumac Rhus aromatica Gro Low 1Mo Mock orange Philadelphus lewisii 1Tg Tall Oregon grape Mahonia aquiolium 3cr Common rush Juncus eusus var. pacicus 13th Tuted hairgrass Deschampsia caespitosa 20w Western escue Festuca occidentalis 10



30/44


yr

sr

Tg

Fc

nzNr

Tg

yr

th

PC

sr


SOUTHWEST OREGON SUN


PC Pacic crabapple Malus usca 1Fc Flowering currant Ribes sanguineum 3Nr Nootka rose Rosa nutkana 3Tg Tall Oregon grape Mahonia aquiolium 6nz New Zealand sedge Carex testacea 14sr Spreading rush Juncus patens 6th Tuted hairgrass Deschampsia caespitosa 8yr Yarrow Achillea milleolium 12


31/44


SOUTHWEST OREGON SHADE


CA Cascara Rhamnus purshiana 1Bt Black twinberry Lonicera involucrata 6Eh Evergreen huckleberry Vaccinium ovatum 8Nr Nootka rose Rosa nutkana 6Tg Tall Oregon grape Mahonia aquiolium 2lp Large-lea lupine Lupinus polyphyllus 2sb Santa Barbara sedge Carex barbarae 16wg Wild ginger Asarum caudatum 12


Eh

CA

Eh

sb

lp

wg

Tg

Nr

Tg

wg

BtBt

lp


32/44


WILLAMETTE VALLEY SUN


SA Sitka alder Alnus viridis ssp. sinuata 1Bh Baldhip rose Rosa gymnocarpa 6Ro Red osier dogwood Cornus sericea 3Rm Rosemary Rosemarinus ocianalis 4dr Dagger-lea rush Juncus ensiolius 25tt Taper-tipped rush Juncus acuminatus 10w Western escue Festuca occidentalis 6


Rm

wf

Ro

SA

tt

Bh

dr

Bh

Bh Bh

Bh

wf

Ro

Ro

Rm

Rm

Bh


33/44


WILLAMETTE VALLEY SHADE


VM Vine maple Acer circinatum 1Dg Dull Oregon grape Mahonia nervosa 14Dr Dwar redtwig dogwood Cornus sericea Kelseyi 9Sb Snowberry Symphoricarpus alba 3ds Dense sedge Carex densa 13br Small-ruited bulrush Scirpus microcarpus 11


Dg

Dr

br

Sb

ds

Dg

VM


34/44


OREGON COAST SUN


PW Pacic willow Salix lucida ssp. lasiandra 1Es Dwar escallonia Escallonia Newport Dwar 4St Silktassel Garrya elliptica 1cs Curly sedge Carex rupestris 32oi Oregon iris Iris tenax 11sl Spanish lavender Lavandula stoechas 13s Sword ern Polystichum munitum 3


cs

Essl

sl

St sf

oi Es

PW

oi


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OREGON COAST SHADE


IP Indian plum Oemleria cerasiormis 1Bb Blue-ridge blueberry Vaccinium pallidum 3Cl Common lilac Syringa vulgaris 1Dr Dwar redtwig dogwood Cornus sericea Kelseyi 6cr Common rush Juncus eusus var. pacicus 8bh Pacic bleeding heart Dicentra ormosa 13ss Slough sedge Carex obnupta 13s Sword ern Polystichum munitum 6


Bb

bhIP cr

Dr

ss

bh

bh

Clsf

sf

Dr


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Rain Garden Plant List: Trees and Shrubs

CommonN

ame

ScientifcName

OregonNa

tive

Willamette

Valley

Coast

Central/Eas

t

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteris

tics

Vine mapleAcer circinatum

Y X X X Xmoderate,

dryshade/

part1520' 1520'

Small, multi-stemmed tree,red-orange all color,excellent soil binder

Sitka alder

Alnus viridis ssp.sinuata

Y X X X wet,moderate ull/shade 315' 1015' Fixes nitrogen in soil

Red osierdogwoodCornus sericea

Y X X X Xwet,

moderate,dry

ull/part 48' 48'Red twigs provide winterinterest, white fowers insummer

Dwar redtwig

dogwoodCornus sericeaKelseyi

Y X X X X

wet,

moderate,dry

shade/ull 2' 2'

Red twigs provide winter

interest, white fowers insummer

Dwar escalloniaEscalloniaNewport Dwar

N X X Xmoderate,

drypart 3' 4'

Evergreen, fowers in latesummer, ragrant

SilktasselGarrya elliptica Y X X dry ull 612' 612'

Evergreen, fowers in spring,berries attract wildlie

BlackhuckleberryGaylussaciabaccata

N X Xwet,

moderate,dry

shade/ull

13' 3'Flowers in summer, edibleberries, likes acidic soil

The Oregon Rain Garden Guide: Landscaping for Clean Water and Healthy Streams36

TREES AND SHRUBS

JimPollock

BrentMiller

LindaMcMahan,

OSUExtension

TeresaHuntsinger

RebeccaGebeshuber

PeteVeilleux

MarielleAnzelone

See page 20 or tips on choosing rain garden plants. Note that plant size will vary by location.Consult your nursery or OSU Extension Service oce or locally accurate size inormation.


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CommonName

ScientifcName

OregonNative

WillametteValley

Coast

Central/East

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteristics

Ocean spray

Holodiscusdiscolor

Y X X X X moderate,dry

ull/part 48' 36'

Flowers in summer,

attractive to wildlie, goodsoil binder

Spanish lavendarLavandulastoechas

N X X Xmoderate,

dryull 1' 12'

Evergreen, pleasantragrance, attractive summerfowers

Black twinberry

Lonicerainvolucrata

Y X X X X wet,moderate part 7' 10'

Yellow fowers in summer,

black berries with bright redbracts, attractive tohummingbirds

Tall OregongrapeMahoniaaquiolium

Y X X X Xmoderate,

dryull/part 4' 4'

Evergreen, yellow fowers inspring, bronze all color

Dull Oregon

grapeMahonia nervosa

Y X X X Xmoderate,

dryshade/

part 2' 2'Evergreen, yellow fowers inspring, berries attract wildlie

Pacic crabappleMalus usca

Y X X Xwet,

moderateull/part

1030'

1030'

Flowers in spring, attractiveto wildlie

Indian plum

Oemleriacerasiormis

Y X X X

wet,

moderate,dry

part 10' 5'

Flowers very early spring,

ragrant leaves, suckeringhabit

Mock orangePhiladelphuslewisii

Y X X X Xmoderate,

drypart 5' 3'

Fragrant fowers attractbirds, butterfies, and bees,prune to shape

3The Oregon Rain Garden Guide: Landscaping for Clean Water and Healthy Streams

Trees and Shrubs

M.S.Yamasaki

EddRussell

KarenHaard

SteveMatso

n

MateAdamkovics

PeteVeilleux

PeteVeilleux

arrowlakelass@fickr


38/44

CommonName

ScientifcName

OregonNative

WillametteValley

Coast

Central/East

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteristics

Pacic Ninebark

Physocarpuscapitatus

Y X X X X wet,moderate

ull/part 613' 613' Unique shredding bark,drought tolerant

CascaraRhamnuspurshiana

Y X X X moderateshade/

ullto 20' to 15'

Shrub or small tree, yellowall color

Grolow sumac

Rhus aromaticaGro Low

N X X moderate,dry ull/part 2' 68' Fragrant, orange-red allcolor

Smooth sumacRhus glabra

Y X X X X dryshade/

ull612' 10'

Orange-red all color,suckering habit

Golden currantRibes aureum Y X X

wet,moderate ull 68' 68'

Frangrant spring fowers,edible ruits

FloweringcurrantRibes sanguineum

Y X X Xwet,

moderate,dry

ull/part 10' 7'Showy, pink fower clustersin spring, attractive to birds

Baldhip roseRosa gymnocarpa Y X X X X

wet,

moderate,dry

ull/part 23' 3' Flowers in summer

Nootka roseRosa nutkana

Y X X X Xwet,

moderate,dry

shade/ull

5' 5'Large, ragrant, showyfowers in late spring, bewareo thorns

Trees and Shrubs


DougWaylet

t

LindaMcMahan,

OSUExtension

PeteVeilleux

PeteVeilleux

PortlandBureauo

EnvironmentalServices

KarliScott

JohnHagstrom

LindaMcMahan,

OSUExtension


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CommonName

ScientifcName

OregonNative

WillametteValley

Coast

Central/East

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteristics

Rosemary

Rosmarinusofcianlis

Y X X X dry ull 3' 3'

Evergreen, fowering begins

in winter, resh or driedleaves used in cooking

Pacic willowSalix lucida ssp.lasiandra

Y X X X Xwet,

moderateull 13' 10'

Male and emale catkins areborne on separate plants

Douglas spirea/

hardhackSpirea douglasii

Y X X X X

wet,

moderate,dry

ull/part 5' 5' Pinkish fower clusters insummer

SnowberrySymphoricarpusalba

Y X X X Xmoderate,

dryshade/

ull6' 4'

Flowers in spring, whiteberries provide winterinterest, excellent soil binder

Common lilacSyringa vulgaris N X X X

moderate,dry ull/part 15' 612'

Showy, ragrant lavenderfowers in late spring

EvergreenhuckleberryVacciniumovatum

Y X X Xmoderate,

drypart to 9' to 8'

Evergreen, edible berries inlate summer, new growthemerges bronze in color,requires acidic soil, prune toshape

Blue ridgeblueberryVacciniumpallidum

N X Xmoderate,

dryshade/

ull 23' 23' Edible berries

Trees and Shrubs

The Oregon Rain Garden Guide: Landscaping for Clean Water and Healthy Streams 3

NOTES:

OregonEnvironmental

Council

NewYorkBo

tanical

Garden

OSUExtension

BruceM.Marshall

NealKramer

OSUExtensio

n

VictorFarinelli


40/44

CommonN

ame

ScientifcName

OregonNa

tive

Willamette

Valley

Coast

Central/Eas

t

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteris

tics

YarrowAchilleamilleolium

Y X X X Xmoderate,

dryull 2' 2'

Summer fowers,spreads by rhizomes

Wild ginger

Asarumcaudatum

Y X X X X moderate shade/part 10" spreading Evergreen, pleasantragrance

Pacic bleedingheartDicentra ormosa

Y X X X Xmoderate,

dryshade/

part2' 2'

Delicate oliage withattractive spring fowers

Purple

conefowerEchinaceapurpurea

N X X X X moderate,dry ull 3' 2' Summer fowers,attractive to wildlie

Oregon irisIris tenax

Y X X Xwet,

moderate,dry

ull 1' spreadingEvergreen, grassyoliage, showy springfowers

Large-leavedlupineLupinuspolyphyllus

Y X X X Xmoderate,

dry ull/part 3' 2'Showy spring fowers,xes nitrogen

Sword ernPolystichummunitum

Y X X X moderateshade/

ull3' 3'

Shiny, leathery,evergreen leaves

Rain Garden Plant List: Perennials

PERENNIALS


JordanMeeter

OSUExtension

JonSullivan

PeteVeilleux

OSUExtension

MichaelG.Sh

epard

FransSchmit


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CommonName

ScientifcName

OregonNative

WillametteValley

Coast

Central/East

Southwest

Moisture

Zone

SunRequirements

Height

Width

Plant

Characteristics

Canada

GoldenrodSolidagocanadensis

Y X X X X moderate,dry

ull 3' 2' Pyramidal fower clustersin late summer

Santa Barbara

sedgeCarex barbarae

Y X wet,moderate ull/part 13' spreading Evergreen, fowers insummer

Dense sedgeCarex densa

Y X X Xwet,

moderateshade/

ull2' spreading

Evergreen, good orerosion control, trappingsediment and slowing thefow o water

Slough sedgeCarex obnupta Y X X X X wet ull/part 25' spreading Excellent soil binder

Curly sedgeCarex rupestris

N X X X wetshade/

ull14" spreading Evergreen

Orange New

Zealand sedgeCarex testacea

N X X Xwet,

moderate ull 25' 1'

Light green leaves

develop red/orangehighlights

Tuted hair grassDeschampsiacaespitosa

Y X X X Xwet,

moderateull/part 2' 3'

Attractive throughoutwinter

Perennials

RUSHES, SEDGES, AND GR ASSES

4The Oregon Rain Garden Guide: Landscaping for Clean Water and Healthy Streams

MartinVavrk

ClaudiaVieira

PeteVeilleux

PatrickStandi

sh

Dr.DeanWm.Taylor,

JepsonHerbarium

PeteVeilleux

PeteVeilleux


42/44

Rushes, Sedges, and Grasses

CommonName

Scientif

cName

Oregon

Native

WillametteValley

Coast

Central/East

Southw

est

Moistu

re

Zone

SunRequirements

Height

Width

Plant

Charac

teristics

Western escueFestucaoccidentalis

Y X X X Xmoderate,

drypart 13' 13'

Inconspicuous yellowfowers and brown seeds.Short-lived (20 years)

Taper-tippedrush

Juncusacuminatus

Y X X X X wet ull/part 3' spreading Drought tolerant

Common rushJuncus eususvar. pacifcus

Y X X X Xwet,

moderateull/part 35' spreading

Tolerant o pollutedconditions. Note thatEuropean sot rush (J.eusus var. eusus) canbe invasive. Please usethe native Pacic variety.

Dagger-lea rush Juncus ensiolius

Y X X X X wet ull/part 2' spreadingFlattened stems muchlike an iris

Spreading rushJuncus patens

Y X X X X wet ull/part 2' spreading Bluish-green oliage

Small-ruitedbulrushScirpus

microcarpus

Y X X X X wet ull/part 4' spreading Good soil binder


SteveMatson

PortlandBureauo


DenisBousquet

KeirMorse

RobertH

.Mohlenbrock,

USDAN

RCS

PortlandBureauo


NOTES:


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For more inormation:

OSU Water and Watershed Education:

extension.oregonstate.edu/watershed/

rain-gardens

East Multnomah Soil and Water Conservation

District: www.emswcd.org

Jackson Soil and Water Conservation District:

www.jswcd.org

Oregon Environmental Council:

www.oeconline.org/stormwater

Andreoletti, Jessica. 2008. The Vermont RainGarden Manual: Gardening to Absorb theStorm. Winooski Natural Resources Conser-vation District. www.vacd.org/winooski/

winooski_raingarden.shtml

Bannerman, Roger, and Ellen Considine.

2003. Rain Gardens: A How-to Manual orHomeowners. UWEX Publication GWQ0371-06-5M-100-S. University o Wisconsin Exten-

sion. clean-water.uwex.edu/pubs/pd/home.

rgmanual.pd

Dunnett, Nigel, and Andy Clayden. 2007. Rain

Gardens: Sustainable Rainwater Management

or the Garden and Designed Landscape.

Timber Press.

Giacalone, Katie 2008. Rain Gardens:A RainGarden Manual or South Carolina. CarolinaCLEAR, Clemson University Public Service.

www.clemson.edu/public/carolinaclear/

Hinman, Curtis. 2008. Rain Garden Hand-book or Western Washington Homeowners.Washington State University Extension.

www.pierce.wsu.edu/Water_Quality/LID/

Raingarden_handbook.pd

Figure 34: Rain garden using a grassy swale as the base. (Photo: Candace Stoughton, EMSWCD)


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Oregon Sea Grant

Corvallis, Oregon

ORESU-H-10-001

Documents

How to Build a Rain Garden