Terrestrial Invasive Plant Species

Habitat Workshop 2010

Carleton College

An introduction to the issues and a few answers (it’s a big topic)

Nancy BrakerArboretum Director – Carleton College

Definition"Invasive species" by MN law, means a non-

native species that can naturalize and:

1) causes or may cause economic or environmental harm or harm to human health; or

2) threatens or may threaten natural resources or the use of natural resources in the state.

(M.S. 84D.01, Subd. 9a)

DefinitionSpecies that have been introduced, or moved, by human activities to a location where they do not naturally occur andcause ecological or economic problems

We live in a highly mobile world

DefinitionAggressive natives vs invasive species:• Native species can also invade a site• Ecological changes can cause native species to

dominate areas where historically they have not

Consequences of Invasive Species

Ecology

Recreation

Economics

Ecological Consequences

• Changes in natural community structure and composition

• Changes in nutrients or chemical composition of soils (allelopathic responses)

Ecological Consequences

• Changes in habitat for birds, amphibians, invertebrates, etc.

Ecological Consequences

• Changes in biodiversity

Ecological Consequences

Recreational Consequences

Scenic and aesthetic changes

Hiking and hunting

Recreational Consequences

Economic Consequences• Damage and control

costs are estimated at $138 billion each year (USDA, 2000)

• In FY09 MDNR Parks spent approximately $600,000 on 226 invasive species control projects

• Average cost per acre for invasive species control is between $250 and $1500 depending on percentslope and infestation

Lost Revenue– Increased management cost

• Herbicide treatments• Timber stand improvement cost

– Loss of timber production• Invasive species may compete with desired

natives– Loss of target species regeneration

• Need to plant and not rely on natural regeneration

Economic Consequences

Types of Pathways

• Human activity– Intentional (nursery stock)– Non-intentional (ballasts, soil)

• Animal activity– Feeding– Travel pathways (garlic mustard)

• Abiotic activity – Floods/Storms– Wind

PathwaysVehicles

Mud in truck tires

Seeds orvegetationin grill

Seeds or vegetation stuck in variousparts of vehicle

Pathways

Foot Traffic Material brought to site

PathwaysRecreation

Horses, bikes, pets, and you canmove species from one habitatto the next.

PathwaysWildlife movement

Ingesting seed or transporting plant materials in their furor on their feet

Planning Your Attack

Survey and Map - Understand the problem

• What invasive species do you have?• What is the scope of the problem?• Keep informed of and look for potential

new problem plants

Mapping

Simple to complex• Hand drawn map• Aerial photo with notes• GPS• Geographical Information

System (GIS)

Planning your Attack

Survey Example

Black Swallowwort

Planning your attack

Develop a plan• What are your control options?• Where do you start?

– Prioritize: small infestations may be more important then largest

• What will you plant instead?– How will you fill the space that you

just cleared out?

Planning your attack

Monitor• How will you keep track of your

progress?• Are you making progress?• Do you need to try some other tactic?

Identification

Herbaceous Plants• Garlic Mustard• Spotted Knapweed• Wild Parsnip• Reed Canary Grass• Thistles

A few of many!

Woody Plants• Buckthorn• Bush Honeysuckles• Japanese Barberry• Black Locust• Amur Maple• Siberian Elm

Identification Buckthorn• Native to Europe• Single- or multi-

stemmed up to 20 ft• Forms canopies in

forest understory • Impacts

– Shades native species– Changes soil chemistry– Reduces regeneration

of tree seedlings and herbaceous layer

Common buckthornRhamnus cathartica

Glossy buckthornFrangula alnus

IdentificationBuckthorn• Leaves sub-opposite• Twigs tipped with sharp

thorn • Buds pressed to stem• Leaves with curved

parallel veins• Berries black with

several seeds

Can be confused with:• Wild Cherry• Wild Plum• American Plum• Grey Dogwood• Red twigged dogwood

Buckthorn

Cherry

IdentificationGlossy Buckthorn• prefers a wetter

environment than Common Buckthorn

• Bogs, fens, sedge wetlands, and disturbed areas

Common Buckthorn • prefers dry soils • open woods, savannas,

clearings, roadsides, and disturbed areas, also invades prairies

IdentificationBush Honeysuckles

(Lonicera spp.)

– Native to Japan– Multi-stemmed, deciduous

shrub– Up to 15 ft tall– Flowers in May or June– Cause declines in native

plant species of woodland and forest communities

Morrow’s

Bells

Tatarian

Bell’s

Identification

Bush Honeysuckles• Open woodlands,

abandoned fields, other disturbed areas; also invades forests, savannas and prairies

• Prefers moister soils, but can be found in drier environments

Morrow’s

Tatarian

IdentificationJapanese Barberry

(Berberis thunbergii)– Native to Japan– Small deciduous shrub 3-5 ft tall

– Slightly curving branches with thin, straight spines. Bright yellow inner bark

– Very small (0.5-1.5 in) green, blue-green, or reddish-purple leaves

– Flowers in early May; bright red berries

– Forms dense stands that displace natives

IdentificationJapanese Barberry

• Prefers well-drained soils

• Oak savanna and oak forest, but grows and bears fruit in full sun to full shade; wetlands -upland forests

IdentificationBlack Locust

(Robinia pseudoacacia)– Native to U.S. (Appalachian)– Deciduous tree up to 75 feet tall

– Seed pods are 2-4 in long; flowers are fragrant and grow in elongated clusters

– Flowers in May and June

– Was commonly planted for erosion control

– Alters nitrogen cycling and competes with native plants

IdentificationBlack Locust Invades woodlands,

savannas, prairies, edge habitats, abandoned fields, and disturbed areas

IdentificationAmur Maple (Acer ginnala)

– Native to Asia– Small deciduous tree to 20 feet

– Twigs are smooth and light

– Turns bright red in fall

– Fragrant flower clusters in May and June produce many seeds

– Forms dense stands that displace native plants

– Planted as an ornamental

IdentificationAmur Maple

• Grows best in moist, well-drained soils with full sun, but tolerates a wide variety of pH, soil, and shade conditions

• Especially successful in open woods and savannas

IdentificationSiberian Elm (Ulmus pumila)

– Deciduous tree to 70 feet– Silver-gray twigs have a zig-zag

shape with leaf bud at each turn – Leaves base only slightly

uneven (compared to American elm with asymmetrical base)

– Invades pastures, roadsides, and prairies

IdentificationGarlic Mustard (Alliaria petiolata)

– Native to Europe

– First recorded in 1933 (UM herbarium records)

– Biennial, herbaceous plant

– Flowers May-June (white)

– Causes declines in native plant species of the forest understory and bottom lands

IdentificationGarlic mustard life stages

Rosettes

Flowering Plants Seed pods

Infestation

IdentificationGarlic mustard

• Prefers disturbed areas; wet, shaded, deciduous woods, floodplain forests

• Also spreads to upland forests and other habitats

IdentificationSpotted knapweed (Centaurea maculosa)

– Native to Europe and Asia– Biennial or short-lived perennial– 3-4 feet tall– Small pale leaves– Single thistle-like pinkish-purple

flower– Tap root– Inhabits dry to wet sandy soils

IdentificationWild Parsnip (Pastinaca sativa)

– Monocarpic perennial– Rosette 6-12”, flowering

stage 4’ tall– Alternate leaves with 5-15

leaflets on both sides of common stalk

– Yellow flat-topped flower (parsley-like)

– Flowers in June thru late summer

IdentificationWild Parsnip

– Spreading widely in MN – mowing roadsides distributes seeds

– May produce severe rash

– Toxic response depends on prior damage to plant

IdentificationReed canary grass (Phalaris arundinacea)

– Planted for forage, silage, and fodder– Invades wetland and floodplain communities, also

found in crop field waterways – Perennial grass– Reproduces from rhizomes

and seed– 2 – 6 feet high– Forms dense monocultures

Identification• Thistles

– Musk thistle• Biennial, 2-6’ tall• Multi-branched stem with

nodding flowers– Canada thistle

• Perennial, 2-4’ tall• Stems branch at top only• Fibrous taproot with

spreading horizontal roots– Bull thistle

• Biennial, 3-6’ tall• Alternate, coarsely lobed

leaves with spines at each tip

Mechanical Control• Pulling• Cutting• Mowing• Grazing• Fire

Pulling• Most species can be pulled

(works better for some)• Soil disturbance may harm

native species or createseed bed for invasives

• Take enough root with the pull (usually root crown)

• Put plant in plastic bag or burn on site (when seed can germinate)

Grazing• Can either promote or

reduce weed abundance• Will not completely

eradicate invasive plants• When combined with

biological control or herbicides it may eliminate the species

Fire• Will sometimes promote

invasive vegetation• Timing and intensity are

important• Most effective before

flowering or seed set• Often used to reduce

litter so herbicide will be more effective

Mowing

• Can be somewhat effective (most usefulwith species that spreadthrough seed and notvegetatively)

• Timing is important—before seed set is most effective

• Like fire, may stimulate invasive species growth

Chemical control• Type of chemical depends on the target species• Always follow directions & wear safety equipment• Broadcast, cut stump, or

basal bark treatments• Research and

know which is most effective, how it works, and how to use it

Biological Control• Available for some species;

research underway for others• Goes through extensive testing• Monitoring the target species

and the bio-control agent is important

• Host specificity testing– Taxonomically associated plants– Plant species growing in the same

habitat as target weed– Important agricultural plant species

(Smith and van den Bosch, 1967; Pearson and Callaway, 2003)

Purple Loosestrife Biological Control

• Releases (1992-2005)• 1735 releases

– 800 sites– 80 million beetles

• Evaluation (2005)– 320 sites visited– 31% significant

defoliation

Purple Loosestrife Biological Control

Buckthorn Biological Control

• Research began in 2001• Potential agents identified

– 5-10 species of interest• Host specificity testing 2003 -

present • 4-6 years of testing remaining

(Gassman et al. 2002)

Garlic MustardBiological Control

• Research began in 1998• Potential agents

– 4 weevil species • Host specificity testing near

completion• First release in 2007 or 2008• Implementation

– Establishing field sites– Developing rearing methods– Releases – Evaluation C. scrobicollis

Tree/Shrub ControlBuckthorn-Honeysuckle-Barberry-Amur Maple-Elm

Control measures include:– Pulling: be careful about soil

disturbance– Chemical

• Treat cut stump with:– Triclopyr—Garlon– Glyphosate—Roundup

• Basal bark spray with:– Triclopyr—Garlon 4

– Burning: long-term management tool to reduce reinvasion

Tree/Shrub ControlBlack Locust-Siberian Elm

Control measures include:– Chemical

• Treat cut stump with:– Triclopyr—Garlon– Glyphosate—Roundup

• Basal bark spray with:– Triclopyr—Garlon 4

– Manual• Elm: girdle large trees, dig seedlings• Locust: mostly ineffective• Burning may reduce re-invasion (seek

out and remove seed trees)

Biennial/Short Lived Perennial Garlic Mustard-Parsnip-Spotted Knapweed

Control measures include:– Pull plant or cut tap root (collect

seed heads)– Cut/Mow before seed production

(not effective with Knapweed)– Summer burn – Chemical: Treat areas of dense

cover with broadleaf herbicide (non-target impacts a problem)

– Burning: long-term management tool to increase native plant cover

Biennial/Short Lived Perennial Garlic Mustard-Parsnip-Spotted Knapweed

Develop a plan that integrates plant biology into the land management tools you use

Seed reduction or elimination is key! Seed may be viable for many years.

Fall: plant dies

1st Summer:develops rosette and large root

2nd Summer: Plant flowers and sets seed

Spring:seeds germinate

Winter: Plant dormant

Mow/Cut/dig

Dig

Herbicide

Growing season burn

Perennial Reed Canary Grass/Thistles

Control measures include:– Dig if very small patch– Chemical treatment of small patches (non-target

impacts a problem)– Cover with shade cloth– Cut/Mow before seed production– Mow multiple times/year– Mow followed by herbicide – Burn prior to herbicide

These are difficult to control, and willtake many years of treatment!

Monitoring

• Can be as simple as photo plots • Can be as complex as experimental designs

testing different management techniques• Monitoring is key to

understanding if we are accomplishing ourmanagement goals

Before

After