USDA Plant Hardiness Zones
Both collard greens and can be grown in most United States Department of Agriculture plant hardiness zones in the spring. To yield multiple crops per year, grow collard greens in USDA zones 8 and above in fall and throughout winter. You can also plant turnip greens in USDA zones 9 and 10 during fall and winter.
Growth Habit and Description
Turnip greens are medium green in color. They grow in mounds or clumps, and most varieties have cut or lobed leaves that are thinner and less textured than collard green leaves. Collard greens can be distinguished from turnip greens by their medium to dark green, or sometimes bluish-green color. Collard greens have a coarser texture than turnip greens, but in their early stages of growth they look similar to turnip greens as they grow in a mound or clump. Once collard greens mature and leaves are picked, it is easier to differentiate them from turnip greens because they begin to grow in an upright habit with leaves at the apex of their long stems.
Growth Season and Timing
Both collard and turnip greens are cool-season vegetables, although collard greens are more cold- and frost-tolerant than turnip greens. While both types of greens can be planted in spring and summer, one major difference between the two is that collard greens grow more slowly than turnip greens. Collard greens can be harvested in 60 to 75 days while most turnip greens take around 40 days to harvest. To harvest collard greens in summer, plant them in early spring, approximately one month prior to the last expected frost. For a fall or early winter harvest, plant them in midsummer, around six to eight weeks prior to the first frost. Plant turnip greens in spring, two to four weeks prior to the last frost in spring, for an early summer harvest or between August and October, eight to 10 weeks before first frost for an early winter harvest.
Both types of greens enjoy substantial sunlight, but can tolerate shade as well. Collard greens thrive in full sun, especially during spring. If the weather is especially hot, they may enjoy light shade. To bring out their best flavor, ensure they get at least 4 to 5 hours of sun per day. Turnip greens grow well in full sun or partial shade.
Both collards and turnip greens prefer well-drained soil that is free of any rocks, twigs or other debris. Likewise, both plants grow best in soil that is amended with organic material. In cases where the soil is clay, add a 4-inch layer of compost and work it into the soil to a depth of 10 to 12 inches to fully nourish the roots. Turnip greens can grow even in sandy soil, although amending the soil is always a good idea for best growth.