PERENNIAL. Tree collards are one of the easiest vegetables to grow in a home garden. For very little input they can provide an abundance of greens all year round. A fast growing relative of collards and kale, they can reach over eight feet in height in a few years. Both resilient and adaptable, they can endure periods of drought by producing smaller leaves, and can even thrive in a large container. Propagated from cuttings in the Longfellow garden!