Tree Collards in the Garden: Managing a Leafy Perennial Crop

Tree Collards, like berry bushes, asparagus, fruit trees, and rhubarb, need their own permanent place in the garden. They need a site where they will not be disturbed by digging and harvesting annual crops. If you already have a section of the garden for berries or the like, that might be expanded to fit collards. 

It's best to think about issues like shade, access, soil quality, and views before you commit to a site. The plants can be anywhere from 3 to 6 feet tall, depending on how you manage them. Staked or trellised as tall plants, they make an excellent screen to hide an ugly view, create privacy, diminish wind, or make a striking background for flowers. They will cast shade--welcome for shade-loving perennials like rhubarb, but a problem for plants like blackberries that need sun. Managed to be lower in height, they will need more space. In In my area, which gets very hot sunny summers, one of the best sites for tree collards is to the east of (not under) fruit trees. They profit from the yearly mulch of fallen leaves and the afternoon shade in summer, while getting full sun in winter when the trees are bare. On the coast, or in climates with cool or cloudy summers, you would want to put them in full sun.

Their bold size and purple-tinted leaves make them a welcome background for flowers, or landscape plant for front yard or patio. Like all brassicas, they like a limey, rich soil and are fairly shallow-rooted. Since they do not require any soil disturbance once they're planted, they could use a space that is too steep, too rocky, too awkward in shape, or too close to hardscaping for yearly tillage and planting. Perennials don't have the need for fast growth that annuals have, and can typically get by with less-perfect conditions of sun, soil, and fertility. 4-6 hours of sun and a yearly application of compost should give them what they need, as long as you keep a constant layer of mulch over the soil surface. The mulch will provide much of their fertility requirement, and minimize the need for water once well established. 
 
Management options: As your plants root and grow, consider how you prefer to manage them. Tree Collards naturally have a woody stem that can get over an inch in diameter, with a cluster of leaves on top. Left to themselves, the stem tends to flop down and crawl around, sprouting more upward stems every few inches. Many growers stake them so that they stay vertical, like palm trees. Each plant then has one main "trunk" with a cluster of leaves on top. Staked plants can be grown fairly close--about 18-24". Intensive growers might have a bed with several dozen of them all staked and each producing its cluster of leaves.
 
Other people prefer to let each plant make many clusters of leaves by allowing it to grow horizontally. In that case, vertical stems will sprout from the main stem every few inches. The advantage is that you get many more leaves per plant. The disadvantages are that they are down on the ground where more leaves are lost to slugs, rot, and other pests. Its harder to get in and fertilize, cultivate, and harvest. And it takes up a lot of space.
 
A very effective method is to grow several plants on a trellis or fence, and train them like blackberries. The main stem of each plant is tied to the trellis so that it doesn't sprawl. But instead of being vertical, like staked plants, the trellis permits the plants to be tied at 45-degree angle. You end up with a row of main stems slanted sideways like this //////////////. The plants can sprout many clusters of leaves, like the horizontal plants do. But they take less space and are more accessible. This method combines high production with space-efficiency, at the cost of more labor to build and maintain the trellis system.

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Preparing for Winter

Winter weather will bring out the purple color and make the leaves quite sweet. However, too much cold will stop production and temperatures under 20 degrees will kill them if prolonged. It is best to plan ahead for winter. Give kelp meal or wood ash in August/September--potassium helps develop cold-hardiness. Mulch the soil well to prevent freezing and heaving. And plan on a cover you can easily deploy when cold is predicted. Or use a row cover for the entire winter.
 
Taking cuttings for further propagation: You may want to increase your collards. Many growers take cuttings every year to bring inside in case of severe winter weather. In my area, tree collards freeze to death about one winter in five.
 
Look for side stems that are firm but not woody, and about 1/2” in diameter.  Remove leaves, and make the cuttings about 8” long. Proceed with potting just as above. During the winter, potted cuttings can live in a sunny window or in a greenhouse. They will need more light than the average houseplant (most houseplants are usually from the jungle floor). Supplement with artificial light if needed.

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