Collard greens are a hardy vegetable that grow best in cool weather. However, they tolerate the heat better than kale, cabbage, or broccoli. Collards are like cabbage without a head. The leaves are harvested and eaten instead.
Collards can be planted directly outside 4-6 weeks before the spring frost date. For an earlier harvest, start seeds indoors 8-12 weeks before the frost date, or purchase transplants.
Transplants are ready when they are 3” tall (8cm). Harden off and transplant outside from 4 weeks before until the week of the spring frost date.
Collard greens can be planted directly outside 10-14 weeks before the fall frost date.
If the temperatures are still very hot, start seeds indoors 10-14 weeks before the fall frost date, or purchase transplants (if available).
Transplants are ready to move into the garden when they are 3” tall (8cm). Harden off and transplant outside 7-8 weeks before the fall frost date.
The plants will mature more slowly in the fall because the days are shorter, but since they can tolerate freezing temperatures, you can continue harvesting after the first fall frost. In fact, the flavor is better after a light frost.
If you live in a mild climate with a late or no fall frost date (after Nov 1), you might be able to grow collard greens all during the winter.
Soil and Fertilizer
Collards grow best in a rich soil; amend with lots of compost and fertilizer (chemical or organic) at planting and every 4-6 weeks during the season.
Fertilizer: 16-16-8 at planting, 21-0-0 every 4-6 weeks.
Harvest outside leaves when the plant reaches 12” tall (30cm).