Two of the easiest-to-grow cabbage family crops, kale and collards (Brassica oleracea) are closely related veggies with similar cultural requirements. You can grow quick crops of kale or collard greens in spring, while the weather is cool, and then plant them a second time in late summer for harvesting after the weather cools again in fall.
If you live where winter temperatures stay above 15 degrees Fahrenheit, you can grow kale and collard greens right on through the winter months. As true biennials, kale or collard plants that survive winter rush to produce flowers and seeds in spring.
Types of Kale
Kale varieties vary in leaf shape and color, as well as overall vigor. ‘Red Russian’ kale produces heavy yields of green leaves with reddish-purple ribs.
Tuscan kales, such as ‘Lacinato,’ produce long, narrow, dark-green leaves with a waffle-like texture.
Numerous curly kale varieties including ‘Winterbor’ and ‘Redbor’ feature leaves with rumpled, curled edges.
Types of Collard Greens
Collard varieties vary in leaf color and texture, as well as regional adaptation. ‘Georgia’ collards grow well in the sandy soils of the Gulf Coast, while ‘Champion’ and other strains bred in Virginia perform better where winters are cold.
Try the ‘Green Glaze’ collard variety, which has bright green leaves and is slow to bolt, if you’re looking for a plant that is both heat-resistant and frost-resistant.
How to Plant Kale and Collards
You can grow kale or collards from seeds sown directly into prepared soil, but especially in spring it’s best to start seeds indoors and set them out under protective cloches four to six weeks before your last spring frost. As long as they are protected from cold winds, kale or collards transplanted into cool soil will quickly establish themselves and start growing.
Kale and collard greens grown in spring often become magnets for pests in early summer, so most gardeners pull up the plants and compost them. Then, in July or August, new seedlings are started that will serve as the fall to winter crop.
Recommended seeding dates for growing kale and collards in fall include late June in New Hampshire, early July in Maryland, late July in Alabama, and late August in Arizona. Harden off the seedlings before setting them out in well-prepared soil, and plan to cover them with lightweight row cover or tulle to exclude insect pests and provide a little bit of shade.
Kale and collard plants are heavy feeders that grow best in moist, fertile soil with a pH between 6.0 and 7.5. Mix in a generous application of a balanced organic fertilizer before planting, and allow at least 12 inches between plants. Use a biodegradable mulch of grass clippings or coarse compost to insulate the roots from any warm weather.
For recommended planting dates for your local climate — and to design your garden beds — try our Vegetable Garden Planner.
Pest Control for Kale and Collards
Featherweight row cover held aloft with hoops or stakes is the easiest way to protect actively growing kale and collard greens from cabbageworms, harlequin bugs, grasshoppers and other summer insects. When the row covers are removed, monitor plants closely for pest problems, and use either a Bt or spinosad-based organic pesticide to limit feeding by leaf-eating pests.
Harvesting and Storage
Begin harvesting when plants’ leaves are larger than your hand, and just break off the older, bigger leaves as you need them for cooking. New leaves will continue to grow from the plants’ centers. After the plants reach harvestable size, most varieties will yield three leaves per plant every five days.
Leaf quality is best in the fall, after the plants have been exposed to a few light frosts. These are the best leaves to blanch and freeze for long-term storage. Kale and collard greens also can be dried into snackable chips.
As biennials, kale and collard greens produce yellow flowers followed by elongated seedpods in their second year. When the seedpods dry to tan, gather them in a paper bag, and allow them to dry indoors for a week. Shatter the dry pods and collect the largest seeds for replanting. Under good conditions, kale or collard seeds will store for up to three years. Be sure to work only with open-pollinated varieties when saving seeds, because hybrid varieties may not breed true from seed.
For growing advice for many more garden crops, check out our complete Crops at a Glance Guide.
Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.