Practicing Eliot Coleman’s Winter Harvest System in Black

Forest by Emmy McAllister,

Copyright 2015. All rights reserved.

http://www.amazon.com/The-Winter-Harvest-Handbook-

Greenhouses/dp/1603580816 Retail price, $29.95. Amazon price, $22.00.

Here in Black Forest, our weather has become more and more unpredictable.

Many of us did not get our cool season crops in until much later this spring. Some

of us even had to wait until mid-June! If this kind of weather pattern continues,

(and even if it doesn’t), we might want to seriously consider adopting some of the

growing practices of world-renown organic market gardener, Eliot Coleman. Eliot

has perfected some simple, inexpensive ways of growing vegetables so that he

can harvest some of them all winter long and the rest of them very, very early in

the spring, long before our spring-sown or spring planted cool weather crops ever

mature here!

We can enjoy harvesting our vegetables at the same times of the year as Eliot,

because winter conditions here are even less challenging than his in Harborside,

Maine, and he wrote all the directions and details for us in The Winter Harvest

Handbook, which was published in 2009. Larry Rutherford has already proven

that the method worked in his Black Forest garden last winter and this spring, so

I encourage everyone to “stumble forward” and experiment! If your first sowing

doesn’t succeed……sow, sow again!

Eliot’s winter harvest system is sun-driven. It requires no heat source except

the sun! Eliot’s Four Season Farm is at 44 degrees north latitude. We are at 39

degrees north latitude, five degrees latitude further south. This means that we

get more hours of sunlight here in the winter than he does. And, incredibly, in

spite of the fact that his farm is at sea level and we are at high altitude, our

average winter temperatures are warmer than his!

There are three components to Eliot’s winter harvest system: 1) Vegetable

varieties that are extremely cold-hardy. 2) Succession planting to provide a

continual harvest, and 3) Protecting the plants under cover while they are

growing. Surprisingly, there are many winter-grown vegetables that need only

the minimal protection of an unheated Cold House or a Quick Hoop. When all

three of these components are used together, there is great synergy!

Here is the link to a two-hour presentation on the winter harvest system given

by Eliot in 2012. The clip from this video that Paul and I showed at the June 14,

2015 meeting ran from about the 9 minute mark to about the 28 minute mark.

Eliot Coleman presents The Winter Harvest Handbook - YouTube

This is our back yard version of Eliot’s large, commercial Cold House.

The sides of the outer covering slide up and down and the ends are quickly removable.

In our backyard gardens, we may want reserve certain areas or raised beds

exclusively for winter harvest use because of the long periods of time that the

winter harvest crops occupy the soil.

Cold Houses are situated on an east-west axis. They need only a single layer of

UV-resistant plastic. The secret to withstanding temperatures of down to 20

below zero is a second layer of protection made of row cover inside the plastic

layer so that the soil itself becomes the heat-storage medium. (You will find the

names of the products Eliot uses, where to get them and what they cost at the

end of this article.)

The rows inside Eliot’s Cold Houses are 30 inches wide. The row covers are

supported by flat-topped wire wickets that hold the row covers 12 inches above

the soil. The double coverage not only retains the sun’s heat, but also increases

the relative humidity underneath, which offers additional protection against

freezing.

The double layer moves the plants 1000 miles to the south. Coleman says, “We

are not extending the growing season. We are extending the harvest season.”

They plant in August, September and October. Many of the plants are

hibernating in the winter, not growing. Plants are harvested young because

younger plants are usually hardier than older ones.

The outer covering: Anti-drip coatings cause condensed moisture to form a thin

film instead of droplets. They let in more light and the thin moisture film acts to

reflect back the heat waves radiating from the soil at night, thus helping to keep

the air inside the cold house warmer.

They make the wickets from lengths of #9 wire. Each leg is 23 inches long, and

holds the row cover a foot above the soil. They pull it tight and clip it to the end

wires with clothespins, (see below). The objective is to keep the cover from

touching the plants.

“Making two visits to one of our cold houses – one at dawn after a below zero night, and the

other a few hours later—provide a striking introduction to the winter harvest. During the dawn

visit all the crops are frozen solid….Yet a few hours later, after the sun, even on a cloudy day,

has warmed the cold houses above freezing, the second visit presents a miraculous contrast—

rows of vigorous, healthy leaves. No scientific data can offer as much information or inspiration

as those two visits to the cold house!” Eliot Coleman

“Too warm” is more damaging to winter harvest crops than “too cold”. So they

wait to put the inner row covers on until just before the weather is cold enough

to freeze the inside of the Cold House, and by mid-March at the latest, they begin

folding back the row covers on sunny days to prevent overheating of the crops

underneath.

They do not irrigate during the winter months.

For growers in Zones 3 to 6, like us, Eliot recommends growing only the most

cold-hardy crops in the coldest months of winter, (mache, leeks, claytonia and

Asian greens), and experimenting with another layer of protection, such as

using cold frames inside the cold houses, which can be covered with old rugs or

mats for extra protection. Some of us are in Zone 6 around here, and others in

Zones 4 or 5. We might not need cold frames, except perhaps for the baby

potatoes and the cabbages.

Cut and come again winter crops like spinach, chard, claytonia, and tatsoi

continue productive regrowth after harvest as long as they have well

established root systems.

The time from planting to maturity triples in a cold house. Limited sunlight and

cold temperatures cause plant growth to slow way down during the winter

months, so knowing the best sowing dates for each vegetable in the fall and

winter is much more important than when sowing seeds in the spring, when the

time from sowing to maturity is much shorter.

This graph shows the effects of reduced sunlight and cold temperatures on a

crop that would normally take 40 days to mature. The same crop required 120

days to mature in the Cold House.

You can use this graph to calculate how many days in advance to plant in order

to harvest at any particular date on the horizontal axis. For example, to plan a

March 15 harvest, find the point on the graph where March 15 lies on the cold-

house curve. From there, trace down to a number on the horizontal axis. That

number, which is 118, means that you would want to plant 118 days before

March 15, (November 17), for a March 15 harvest.

The formula for this calculation is based on the ratio between the day length at

our latitude and his. The National Weather Service web site offer instant day

length calculations for any location:

www.srrb.noaa.gov/highlights/sunrise/sunrise.html

Since we are south of Eliot’s garden, at around the 39th parallel, and Eliot’s

garden is approximately at the 45th parallel, we get more hours of sunlight each

day in the winter than he does, and we could decrease our expected number of

days from planting to harvest accordingly. But 39 divided by 45 = .8666, or only

about one day. So we could use Eliot’s chart just the way it is, without even

subtracting a day.

Winter crops grown in the Cold Houses, where there is easy access to them all

winter long for harvest:

Mache: Vit

Miner’s lettuce (claytonia)

Beet Roots: Touchstone Gold, Red Ace and Merlin

Beet Leaves: Bull’s Blood and Red Ace

Spinach: Space and Palco hybrid. Overwintered spinach has become Eliot’s

major winter green crop. It produces new leaves all winter, unlike kale, for

example.

Endive: Bianca Riccia

Lettuce: Oak leaf red lettuce, Rouge d’hiver, Red Salad Bowl, Tango, Rex

Arugula: Sylvetta and Astro

Swiss Chard: Fordhook Giant and Ruby Red; “narrow stem” Swiss chard, (butter

chard), harvested when the leaves are the size of a man’s hand.

Carrots: Mokum, (candy carrots), Napoli and Nelson

Asian greens, (the hardiest of all winter greens): Komatsuna, Tokyo Bekana,

Tatsoi, Pak Choi, Mei Qing Choi; Mizuna

Leeks: Tadorna, (don’t even need the second covering)

Scallions: White Spear

Onions: Short day onion varieties plus Walla Walla and Olympic, which are

overwintering varieties

Turnips and turnip greens: Hakurei hybrid variety, small and sweet

Potatoes: Rose Gold baby potatoes – Sprout indoors in mid-to late February at 70

degrees for a week to break apical dominance and increase the number of

sprouts. Plant around St. Patrick’s Day, March 17, in a Cold House. Plant two rows

down a 30” wide bed. May need an extra cover at night if temperatures threaten

to freeze under the row cover. For that reason, consider growing the potatoes in

a cold frame inside the cold house instead of under row cover inside of the cold

house, so the roof of the frame can support the extra covers. It takes only two

months for baby potatoes to reach harvestable, golf-ball size. Harvest in mid to

late May.

Quick Hoops for protecting low-growing, overwintered crops:

Crops that are actually harvested during the winter, like some varieties of leeks,

require the easy access provided in a Cold House. But low-growing,

overwintered crops, grown for extra early spring harvest, like overwintering

onions, scallions, spinach and lettuce and many others listed later in this article,

could be protected by low, inexpensive, temporary structures called “Quick

Hoops”.

Eliot plants overwintering onions during the last week of August and places the

hoops and row cover over them in mid-October. The advantage of overwintered

onion varieties is that the bulbs mature the end of June, providing a spring

harvest as well as the traditional fall harvest.

The supports of the Quick Hoops are 10 foot lengths of half inch electrical

conduit, either plastic or metal. Bowed into a half circle, they nicely cover two 30

inch beds side by side with a path between them.

Eliot inserts each end of the conduit about ten inches into the soil on either side

of the two beds, forming a hoop about 30 inches high at the midpoint. Plastic

conduit can be bent as you put each support in place; metal conduit must be pre-

bent to the ideal shape with a tubing bender.

He places one hoop every five feet along the length of the beds. The hoops are

them covered initially with ten foot wide spun bonded row cover held down by

sand bags placed every five feet along the edge. Later, when real winter

weather threatens, he adds a sheet of ten foot wide clear plastic over the row

cover to make the quick hoop tunnels more snow proof. (See the companion

article on our website describing the process in more detail. It is called,

“Coleman’s ‘Quick Hoops’ (Double-Covered Low Tunnels -- The 2007 Version”).

To stiffen the structure against wind and snow load, it’s important to tighten the

plastic. (In the video we showed at the June 14, 2015 meeting, Eliot describes

how they now use the A frame shape instead of the bow shape because it sheds

snow much better and therefore has much less chance of collapsing under the

weight; but the low, bow-shaped tunnels would probably work best for our

climate due to strong winter winds and much less snow.)

When spring arrives, Eliot starts ventilating Quick Hoops on sunny days. He

removes a few sand bags along the southern edge and inserts a notched prop to

hold up the edges of the plastic and fabric. Once outdoor temperatures have

moderated to the point where the fabric alone is protection enough, he removes

the plastic layer and stores it until next winter. Here in Black Forest, we might

opt to just fold them down and keep them ready to pull up and over to protect

our plants against hail. Quick hoops can be disassembled and moved to cover

other crops later in the spring.

New Opportunities for Northern Growers

Because of the low cost of cold houses and Quick Hoops, northern growers now

have the opportunity to explore late-fall planting of spring crops, a growing

strategy that growers in warmer climates, like the Puget Sound area where I

came from, routinely use.

To take advantage of this opportunity, we need to know:

1) How early we can plant certain fall-seeded crops to have them mature

earlier in the spring without triggering them to go to seed rapidly as the

weather warms up. In other words, we need to know the initial planting

date for each crop and the planting dates we would choose for each

successive planting of that crop to get continuous harvests. We would

use Eliot’s graph to help us figure this out.

Since the sowing and planting date charts for 6000 feet elevation and

7400 feet elevation shown on our website have been unreliable this year,

it would probably be best to decide on our sowing dates by using the

germination temperature tables on our website instead. In other words,

taking the soil’s temperature at dawn, before it has had time to warm up

to determine whether the soil is warm enough to germinate that crop’s

seed.

2) At what size or stage of growth each kind of young seedling is the

hardiest, for surviving the cold winter weather. (Eliot gives us this

information in his book. I hope to compile a chart for this information.

3) What crops can be sown just before the ground freezes, to overwinter as

seeds and germinate extra early in the spring, like our winter wheat did

this year.

4) What crop varieties can be overwintered -- that is, started in the late

summer or early fall to hibernate through the winter, and then start

growing again early in the spring to yield a very early spring harvest. (See

a list of overwintering varieties below. This list is not all inclusive. The

Fall and Winter Territorial Seed Co. catalog offers many of these varieties

because they overwinter well in the Pacific Northwest without any winter

protection at all in many cases.)

Varieties that could overwinter well in Quick Hoops or Cold Houses:

Onions: Walla Walla Sweet Onions, 125 days OP. TS; Olympic; Gatekeeper

Onions, 150 days, F1 hybrid. TS; Stockton Early Reds; Sweet Winter Onions; Red

Marble Onions, 93-105 days, OP. TS;

Scallions: Winter White Overwintering Bunching Onions 120 days OP. TS; White

Lisbon Overwintering Salad Onions, 60-120 days, OP. TS; Welch Onions; White

Spear Scallions; Kujo Multistalk; Shimonita;

Leeks: Giant Musselburgh produces a thick, white, tender stalk two or three

inches in diameter. You can succession plant in the cold house for baby leeks

through the next summer, or let them overwinter under Quick Hoops until they

mature in 105 days. Eliot uses the Todorna variety. They don’t require a row

cover in the cold house. Other winter varieties include Alaska from Stokes;

Giant Winter; Carentan, (extremely hardy), and Winta TS.

Garlic: Many hard neck varieties.

Cauliflower: Overwintering to Spring Harvest Blend from TS. Open pollinated.

Broccoli: Purple Sprouting; Tyfon: A sweet-tasting sprouting broccoli-type tall

plant. Most biomass per square foot of garden space. People and chickens love

eating this crop!

Cabbage: Sow in September and overwinter in cold frames in the Cold Houses.

Remove the frames when the cabbages get too tall, OR grow under Quick

Hoops, which are about 30” tall at their peaks. Jersey Wakefield, April

Monarch, First Early Market, Filderkraut, Berra Tronchuda.

Carrots: Merida Overwintering F1 Hybrid, 240 days for growing under the

Quick Hoops TS. Mokum, (Candy Carrots), and Napoli, the varieties that Eliot

grows in his Cold Houses, are not overwintering in the true sense of the word,

because they mature in the late fall instead of early spring. Once they are

mature, they are covered with straw and then dug as needed all winter.

Spinach: Palco F1 Hybrid can be grown under a Quick Hoop or in a cold house

for easier access. 38 days. Multiple cuttings. Great variety for baby spinach.

Parsley Root: Halblange 120 days. TS OP.

Lettuce: Arctic King Butterhead OP 150 days. TS

Tools and supplies from Johnny’s Selected Seeds in Winslow, Maine,

www.Johnnyseeds.com 1-877-564-6697 Catalog page numbers are listed

below.

Clear plastic outer covering: Tufflite 4 mil Nursery Clear Greenhouse Film. UV

resistant and ultra clear. Extremely durable. 10 feet X 100 feet, $82.95. A great

candidate for a group purchase! Page 194.

Row cover: Quick Hoop initial covering: Agribon AG-19 Floating Row Cover for

frost protection and overwintering. Light transmission, 85%. 10’ X 50 feet,

$31.15. Cut in half to provide a 5 foot Inner covering over wickets for Cold

House crops in 30” beds. Page 200.

Clamps for securing plastic and row cover to conduit hoops: Snap Clamps for

1/2” PVC pipe. Pkg. of 10 for $5.45 Page 194.

Wiggle Wire Connection System for connecting plastic, row cover or shade cloth

to framework. Four foot section of Wiggle Wire, $1.75. Eight foot channel

section, $9.25. Page 196.

Coiled #9 Galvanized Wire for wickets inside of Cold Houses: 60’ $29.95. Page

201. Cuts easily with a bolt cutter.

Locally sourced materials:

Electrical conduit for Quick Hoop frames: either ½” PVC or metal pipe

Wire for wire wickets that support the Agribon row covers inside the cold

houses: Either 76” long straight lengths of # 9 wire made by Ken-Bar, Inc. and

carried by most greenhouse dealers. To locate a local dealer, contact Ken-Bar,

Inc., Peabody, MA 800-336-8882 or www.ken-bar.com

Sources for specialty materials: 6 foot wide metal row cover hoop benders:

Lost Creek Greenhouse Systems, Mineola, TX 903-569-8541 www.lostcreek.net