Many vegetables of the same genus can cross with one another. In the case of brassicas like cabbages and kale, the different species can naturally create hybrids – like tree collards, for instance. The collard green tree is a subspecies called acephala. It is derived from Brassica oleracea, or wild cabbage. It is a perennial or partial perennial, meaning it can live for several years. Hence its alternative name of perpetual kale.
Tree collards are also known as tree kale, kale tree or tree cabbage. Whatever the name, the kale tree has all the flavor and nutrients of kale, collards and cabbage. While it tastes closer to a kale, there are definite cabbage notes and a hint of the pepperiness of collards. In mild climates, these plants have been known to live for 20 years. In colder climes, their life span is less but they can still persist for several years with some protection. The plants can grow up to five feet (1.5m) in height and produce delicious leaves for years.

Care for Tree Collards -
While perennial kale is a brassica and shares many of the cultivation needs of its leafy cousins, there are some key needs to bear in mind for the healthiest plants:
Lighting Conditions: Tree collard plants prefer a full sun site, but in moderately shaded areas, they actually produce more tender, flavorful leaves. Afternoon shade or dappled light is ideal in southern climates.
Watering: Provided the soil is rich and fertile, the kale tree has moderate water needs. In low moisture situations, the plant has an adaptation which prevents moisture loss through the leaves. It develops a powdery coating on the leaves which reflects light.
Temperature & Humidity: Tree collards thrive in high humidity areas, but they are also adaptable to more arid zones. Their temperature tolerance is vast. Some varieties can tolerate temperatures as low as 14 degrees Fahrenheit (-10°C). Most of the varieties should not experience temperatures below 30F (-1°C) or they could die. Some varieties can tolerate temperatures into triple digits (38°F) during summer.
Soil & Compost: Almost any soil is capable of hosting a tree kale. The best growth will occur in well-draining, nutrient-rich soil, but they are capable of thriving even in heavy clay. While the plant does well in acidic soils, the application of lime several months prior to planting will result in better tasting leaves.
Fertilizer: Where the soil is fertile, the plant needs little supplemental food. In poor soils, apply green manure or well-rotted animal manure as a side dress annually. A calcium supplement is recommended annually in the form of ground oyster shells or chicken shells applied around the root zone.

Problems, Pests & Diseases
Root rot can occur in heavy soils and where percolation is poor. Like all brassicas, the cabbage looper is a common pest. These larvae of the cabbage butterfly can wreak havoc on the leaves with their feeding. Hand remove the larva or apply Bacillus thuringiensis. Some animals such as mice and rabbits will feed on lower leaves.

Pruning and Repotting
Left unpruned, tree collards develop into tall, spindly, leggy plants with few leaves. Prune back to the first leaf axil to promote stronger branches and more leaf production. This should be done every few months. Container-grown plants should be repotted every year or two. Replace the soil with the same variety or a good potting soil. Fluff up the roots at transplanting time, and cut out any that are discolored. Stake the plant for best results.

Propagating Tree Collards
Tree kale is propagated by stem cuttings. Take cuttings from either the main stem or secondary shoots. Remove a 1-inch (2.54 cm) wide 12-inch (30 cm) long piece of the tip of a stem. Remove all the leaves except 2 or 3 at the tip. Plant vertically with ⅓ of the top of the cutting outside the soil. Keep the cutting moist but not soggy. Rooting occurs in about six weeks.

Harvesting Tree Kale
The young leaves are the sweetest, but all the foliage can be eaten. Never take more than a third of the foliage. Use young leaves in salads, while older, larger leaves are best cooked. Harvested leaves will keep for several days in a plastic bag in the vegetable crisper. As well as salad, the leaves are excellent added to soups and stews, or sauteed as a green vegetable. Use them anywhere you would use cabbage. The thick leaves may be steamed and used to wrap other foods such as meats.