Tree collards! They are big, beautiful, and edible; perhaps even better they do not need to be grown from seed every year. Tree collards are a fantastic plant for the vegetable or flower garden and are very easy to maintain. The varieties I grow are several variations on purple tree collards, both the original purple tree collards and several hybrids with other kale varieties. There are other cultivars though: you can find seeds that will give you a wide variety of offspring, as I will discuss below, and you can order cuttings of others online.
The word ‘perennial’ might not actually be the best way to describe many genotypes of tree collards and perennial kale. These long-lived varieties are indeed perennial, but they are also often monocarpic. This means they will flower once and then die, a process that can take several years. This gives the plant the appearance of being a perennial in the sense most gardeners think of, and often causes surprise if the plant does manage to flower and then fade away immediately after. Gardeners don’t necessary expect a plant that has lived several years to die upon flowering. Perennial monocarpic kales should have the qualifier of ‘reluctant to flower’, a trait that has pleased gardeners and vexed plant breeders for quite a while. Some varieties can flower many times, however, though they are usually reluctant to do so.
Attractiveness:
Tree collards is an attractive plant. If grown from seed, the plants can be highly variable. The leaves are often colorful, with purple or white veins and large dark green leaves that often have a purple tint. The leaves come in a variety of shapes, sometimes being ruffled or crinkly. These kinds are harder to use as a food, however. The plants can get tall, and with support can reach upwards of 5 feet.
Ease of Cultivation:
In our climate, very easy. The plant survives with almost no irrigation in the summer once established: given that in the PNW we usually get nearly no rain after June, this is pretty impressive. You will get no harvest if you don’t give them lots of summer water, however, and the plants will look very sad until fall rains. The variety I have is also very resistant to the nasty aphids that decimate my biennial kale varieties in the late summer.
They grow very well from fall to spring. The temperature here regularly dips below 18 degrees and I have yet to experience cold-related plant death. They put out lots of tasty leaves off the summer rain and are not particularly vulnerable to slugs.
For maximum yield, dress plants with compost and provide the fragile canes with support. Tree collards suffers in the wind, so keep relatively sheltered and trellised to avoid issues. The plant is referred to as a perennial but plants don’t seem to live too much longer than 5 years or so. Definitely keep several plants and propagate them regularly.
Ease of Propagation:
Pretty simple, as the plant grows very well from cuttings. Select thick cuttings, at least the diameter of a pencil, from new growth with at least two nodes (preferably more). Dipping in rooting hormone is not necessary but I have found it helps. Pot out cuttings into individual containers filled with potting mix: the new roots break very easily, so cuttings can be very difficult to separate without damaging them. Plant out once the plants are well rooted and actively growing.
Growing from seed can be more challenging. One of the reasons the plant is perennial is that flowering is very rare, if it happens at all. You can buy perennial kale seed mixes online, which are usually the offspring of tree collards/perennial kale, Daubenton kale (another special perennial variety), and mixed biennial varieties. A high percentage of the offspring will be annual and die after flowering, but you will definitely get some long-lived progeny with some interesting traits. If your plant does flower expect the same – some biennial offspring, some that might make it a year or two before petering out, and some that are truly long-lived (for a kale).
Ease of Harvest and Storage:
Simply cut leaves off. The leaves are smooth, so washing isn’t too hard, and store well. In the humid, cold environment of a container in the fridge they can keep a week or so.
Taste:
Very good. Tree collards beats most other kale varieties I’ve grown, with almost no bitterness and tender even when the leaves are older. This is a good kale to eat raw in salads. Because of the purple tint I also assume they contain larger amounts of anthocyanins than most green kale varieties, so they might be more nutritious.
Overall:
A fabulous plant for our climate and an excellent kale for eating raw or cooked. Its perennial nature, drought and pest resistance, and quick winter growth makes it a low-maintenance alternative to biennial kale that provides plenty of leaves even in the dark cold of late winter. The only downside is a lack of tolerance to extreme cold: I’ve heard that temperatures below 15 degrees Fahrenheit are not tolerated well, though mine have survived a bit colder. In most of the PNW this shouldn’t be a huge issue, and the plants are so easily propagated that the loss of a few plants can be compensated for with some planning.