Text by Brian Barth
The list of perennial vegetables commonly grown in North America runs pretty short. Asparagus, artichokes and rhubarb may be the only three that most gardeners can name. Other than fruits, not many perennial food plants have tempted our taste buds enough to warrant mass production. It’s so strange, then, that our small stable of commonly grown vegetables doesn’t include that tree collards—a delicious, easy-to-grow member of the Brassica clan.
Tree collards can grow up to 10 feet or more, but they’re easily maintained as a 4-foot “shrub.” That’s not to say they look particularly shrub-like. They typically grow on a single spindly stalk with a crown of large collard-esque leaves that cascade from the top like a little pom-pom. Purple shades the foliage and the new stems. In the kitchen, tree collards offer as good, if not better, culinary traits than any other brassica vegetable. Lacking any of the oxalic acid that makes most brassicas slightly bitter, tree collards taste slightly sweet and nutty, even when raw, and their tender stems don’t get stringy when you chew them. They compare to baby kale as a salad vegetable, but you can use the mature leaves, which grow up to 10 inches in length. Substitute them in any recipe that calls for kale or collards.
These days, you’ll have no trouble finding a source of tree collards on the Internet, but make sure to seek out varieties with a strong purple coloration, as these are the sweetest and most robust. Pure green varieties most likely descend from perennial kale relatives (of which there are several), which have rightfully remained in obscurity because they are neither as palatable nor as vigorous as tree collards. However, tree collards are sometimes labeled as tree kale.
How to Grow Tree Collards
Tree collards grow best given the same environment preferred by any other brassica: full sun to dappled shade, rich soil (not too acidic) and ample irrigation. But being a perennial plant, they require some specific pruning and training, as well as ways to integrate them in the overall garden design.
Left to their own devices, tree collards don’t remain vertical; they fall over and become a tangle of arching stems. Thus, most gardeners choose to train them up a stake, which encourages a neat crown of foliage at the top, like that of a rose standard. You can choose the height you want and keep cutting them back to that point every year, a technique that makes this otherwise gangly plant worthy of a front-and-center position in the landscape. For a lower maintenance patch of tree collards, plant rooted cuttings 18 inches apart and cut them back to a height of 12 inches twice a year—this creates a short, stout trunk capable of supporting the weight of the leaves.
Tree collards are hardy to around 20˚F; they also grow easily as a container plant that can be brought indoors for winter in colder regions. They may also be grown as an annual and perpetuated through cuttings taken each fall, rooted indoors and set out again in spring. Like their collard cousins, tree collards tolerate heat better than most brassicas and they can be harvested in any month of the year.
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