John Jeavons is the Executive Director of Ecology Action, a 501(c)(3) organization headquartered in Willits, California. He is known internationally as the author of the best-selling book “How to Grow More Vegetables—and Fruits, Nuts, Berries, Grains and Other Crops Than You Ever Thought Possible On Less Land Than You Can Imagine”, as well as author, co-author or editor of 200 other “how-to” books, booklets, topical papers and DVDs on related topics about food and sustainable soil fertility growing. For the past 44 years Jeavons has devoted his time to research, develop and teach a small-scale, resource conserving agricultural method — GROW BIOINTENSIVE®. His high-yield food raising approach is being successfully practiced in 151 countries in virtually all climates and soils where food is grown, and by organizations such as UNICEF, Save the Children, and the Peace Corps.
You may have heard of it, or seen it at the farmers markets, but if you haven’t we are sure that you soon will came across this amazing plant! Different strains are known as Tree Kale or Walking Stick Kale, Tree Collards (Brassica oleracea var. acephala) are the “tall cousins” in the cabbage family. They grow upwards like a tree, and some plants can reach up to 12 feet tall!
HISTORY AND USE
Tree Collards were introduced to California, probably during the latter half of the eighteenth century, from the island of Jersey in the English Channel where they were grown to feed cattle.
They are super nutritious, very high in calcium, and here at Ecology Action we have been doing practical research on this wonderful veggie since 1982. We found out that a 100-square-foot bed of tree collards can provide 4x more protein and 8x more calcium than the milk produced from a grain feed crops grown in the same area. In addition, tree collards contain no oxalic acid; therefore, they may be eaten raw without iron being tied up.
As perennials, tree collards can thrive for four to five years (and longer), but it is best to rotate them after three years, since they remove so much calcium from the soil. You should consider taking cuttings, planting a new bed, and getting it established, before removing them completely.
They grow well in most temperate climates, although there may be approximately 75% die-back if temperature drops to 18°F and stays there for any length of time. In this kind of environment, take cuttings at least one month before the first hard frost (or use prunings), flat them and keep them in a greenhouse to overwinter; one month after the last hard frost in the spring, transplant the cuttings. A relative of tree collards, sukuma wiki, does well in tropical areas.
Tree Collards along a fence in Willits, CA. Photo: Renata Abbade
Tree collards are most easily propagated from cuttings. They rarely go to seed and when they do, the chances that a cross with another Brassica is good, for example with wild radishes.
To make cuttings you should cut off a healthy, non-woody branch that will provide two or more cuttings. It is possible to get as many as six cuttings from a good-sized branch that has closely spaced nodes. Clean off all but the upper 1 to 2 leaves.
Each initial cutting must have at least six growth nodes. (A growth node is the scar left after a leaf has fallen off or been removed.) A cutting may be as small as 4 to 6 inches long, if the nodes are closely spaced. A 6- to 8-inch cutting is optimal, but more than 12 inches is not desirable. Make sure each cutting has 6 to 8 nodes. This is very important! Once you have grown a mature plant, you will have an abundance of cuttings to share with your gardener friends!
To root each cutting:
Determine the right side up: the more curved part of the node is at the bottom; the place where the new leaves/roots will come out is at the top. Make sure the nodes look more or less like a heart or a smile. It is useful to cut the top of the stems at an angle, as to not retain any water and avoid rotting; and to cut the bottoms flat to help you remember which way to plant it. When you are ready to flat the cuttings, cut off about 1 inch from the bottom of each cutting—make sure you cut just below the next node up from the bottom. This enables water to be picked up more easily from a fresh, clean cut and a good root to develop.
Examples of healthy cuttings. Photo: Renata Abbade
Put the cuttings on 1.5- to 2-inch centers in a 3-inch-deep flat with mounded soil. Make sure at least 3 nodes are under the soil (roots will come from these), and 3 nodes are above the soil (leaves will come from these). Leave the flats in partial shade. For summer cuttings, put the flats in full shade for the first 4 weeks. Keep them evenly moist.
It can take 2 to 4 months for the cuttings to fully root, depending on the time of year. A cutting is ready to transplant when it has 3- to 4-inch-long roots forking from the nodes under the soil or from the bottom of the cutting, and 2 leaves growing from the nodes above the soil.
The best time to transplant is early spring, while the temperature is still mild. If it is too hot, the plants will be stressed and have difficulty more getting established. Each seedling should have one strong stem; remove any others. Avoid starts with multiple stems.
Twelve-inch spacing works best for an optimal edible yield, plus ease of harvest, in a Biointensive bed. On 9-inch centers, the leaves are smaller, and it takes more time to harvest a given amount of leaves. On 15-inch centers, the stems and leaves are bigger, but the yield is good and a cooks dream for easy preparation, yet and it is more difficult to market larger leaves.
Tree Collards on a bright day at Ecology Action’s GROW BIOINTENSIVE®
Research & Education center in Willits, CA. Photo: Renata Abbade
Transplant the cuttings on 12-inch hexagonal centers in a well-prepared bed which has been double-dug and fertilized with compost. Use a hand trowel, 6 to 8 inches long and 2 inches wide, to open a hole deep enough for the roots and place 2 to 4 unrooted nodes under the soil. There should be at least two leaf nodes above the soil. The plant may grow over 9 feet tall, so the cutting needs to be deep enough for the roots already formed to anchor the plant firmly and for other roots to develop from the stem as well. Planting 2 to 4 unrooted nodes beneath the soil will increase the tall plant’s stability later.
To stake tree collards:
Immediately after transplanting, push an 8 foot x 1 inch x 1 inch stake 18 to 24 inches into the soil, about 2 inches away from each plant. This is easiest to do from one row to the next, before the planting board is moved backward. Be careful not to exert too much pressure on the stake, as it can snap, leaving a sharp point. If the bed is on a slope, it is generally better for the stake to be uphill of the seedling.
When all the stakes are in, drape 30% shade netting over the bed at least until the mini-climate is established, i.e., until there are enough leaves for the plant to thrive. Shade netting can be left on during the hot summer to create a healthier environment for the plants. Remove the shade netting in the late summer or early autumn as the weather becomes cooler.
When the plant is about 18 inches tall, use heavy twine to tie a loose figure-eight loop around the stake and the plant, about 12 inches from the ground. As the tree collard gets taller, tie a loop 18 inches above the last loop periodically, so that the plant always has adequate support.
Optimal 12” spacing, and stakes for support every 18”or so. Note that we have inter-planted some nasturtiums with our Tree Collards! Photo: Mike Pearce
Tree collards are best for eating and marketing during the cooler months; here in Willits, CA that means approximately mid-October to June. The sweetest-tasting leaves are the ones harvested after a light frost.
What to harvest:
Harvest the larger leaves that are about 60% green and 40% purple. This will give you higher yields! Also, the green leaves are not as sweet. Always allow at least 5 central reasonable sized leaves to remain at the top of the stalk (6-8 leaves in winter), this will ensure your plant stays alive because there are enough leaves left on the plant to enable photosynthesis. On a stem with a lot of small leaves, remove approximately one-third of the leaves. Leave the bottom purple leaves on the plant to fall off. If they are removed, the next leaf upward will turn purple the next day, thus reducing your yield.
About 60% green is the best time to harvest (leaf on the left). This is when they are the most delicious! Photo: Renata Abbade
How to harvest:
Break off the leaf at the node by snapping it downwards gently but firmly and easily. Do not pull it down slowly—it can peel off part of the stem. The leaves snap off more easily if they are harvested in the morning or evening when it is cool.
During the first year of growth, tree collards may grow 3 to 4 feet tall before winter comes. The following year, they may reach 6 to 10 feet tall.
Ecology Action’s Garden Manager Matt Drewno stands happily next to his 9’ tall Tree Collards at Green Belt Garden in Mendocino, CA. Photo: Matt Drewno
When to prune:
Tree collards should be pruned 2 to 3 weeks before the hottest summer heat—in Willits, that means about the end of July or the beginning of August. This will give the plant enough time to regrow for the winter harvest to begin in November or December.
How to prune:
The goal is for the plant to produce fewer medium to large leaves rather than a lot of smaller leaves, for ease of harvesting and marketing. In our experience, pruning the plants just above a node, to 2 feet high the first year of pruning, 2.5 feet high the second year, and 3 feet high the third year, gives the best yields over time. Even if the first-year plant is not much over 2 feet or even under 2 feet, it is best to prune it back, so that it does not grow too fast and produce too rapid tall weaker growth the second year. Be sure to cut at an angle into green wood, so that the plant will let water flow off the cut easily.
Prune out thin, weak, woody, bent or twisted stems. Leave the 3 to 4 healthiest and strongest stems that are “evenly radial” leaders (more or less evenly spaced around the stem) and remove the others. If there are no strong stems, go back 2 to 3 months later, prune off the smaller shoots, and leave 3 to 4 strong, evenly radial stems. Leave any leaves on the remaining plant stems, but remove any small branches. Be sure the pruned stems are tied securely to their stakes with string in a figure-eight loop.
Loosen the soil carefully with a border fork 3 to 4 inches deep between the tree collards and around the edges of the bed, to aerate the soil and let water in more easily. Be sure not to disturb the plant roots in the process. Water well (approximately 6 min. per 100 sq. ft.).
Cover the bed immediately with shade netting, to protect the pruned plants from excess heat, if necessary, until the new leaf sprouts are about 3 inches long. Water them at midday to help them regrow and keep them cool until the mini-climate is re-established.
One to two months later, prune off any small branches growing below 2 to 2.5 feet. Prune off smaller stems above this level if a lot of small stems shoot out after pruning, but be sure to leave 3 to 4 strong, evenly radial stems.
After pruning, add the stems and leaves to your compost pile and give it a calcium boost! Your other plants and your bones will love you for it!
EATING (The best part about them!)
Tree collards are fun to cook with, and can be used raw or cooked in any recipes that call for kale, collards or cabbage, and are especially good in soup and sauces! They take a bit longer to cook than kale. You can also eat the stems. They are generally twice as sweet as the leaves, and are nutritious as well.
Salad: Finely chopped raw tree collard leaves may be added to salads, but because they tend to be tougher it is nice to massage the leaves with some vinegar or citrus juice.
Sautéed: Stack your tree collard leaves in a pile and roll them together to create a tight bundle – this makes chopping a whole lot easier! In a large skillet sauté some finely sliced garlic and add the tree collards. Cook on high heat for about 3 minutes. You may also want to add some balsamic vinegar or red wine when the pan is very hot to add some flavor!
Steamed: Sauté onion and garlic in large pot. Add chopped tree collard leaves and a small amount of water. Cover pot closely. Stir after about five minutes and continue steaming until tender.
Tree Collard Pancake: Mix together steamed tree collards, mashed potatoes, sautéed onions, and garlic. Form a large pancake or several smaller ones. Brown lightly in hot oil.
Tree collards are also wonderful in tomato sauce or gazpacho, especially if you need an extra nutrition boost! Photo: Renata Abbade