Perennial vegetables are an essential part of the sustainable garden, and one that can be harvested year-round is invaluable. Purple Tree Collards is just such a plant, offering continuous harvests regardless of the season. This incomparable plant grows 6-10 feet tall and up to 3 feet wide with big leaves up to 10 inches long. These blue-green leaves take on a purple coloration, especially in cool weather, and are tender, sweet and nutty for fresh or cooked dishes. This especially tasty and vigorous variety will yield lots of fresh greens for years and is hardy to about 20°F or zones 8-10.