How to Plant, Grow, and Save Seeds from Collards (Brassica oleracea)

While collard greens have traditionally been enjoyed in the American South, this hearty Brassica oleracea plant grows well in many regions around the United States. Collards produce enormous edible leaves from summer through fall.


Collards are among the most resilient Brassica crops. They can thrive throughout long, hot summers and endure into the fall and winter longer than most garden crops. Plants may be transplanted to the garden anytime after the danger of hard frost has passed.

Sow seeds indoors, 4-6 weeks before transplanting. Sow seeds ¼” deep. Seeds should germinate in 3-10 days. Transplant collard seedlings outdoors just before or anytime after the last frost of the season. Collards need a lot of space to grow. Plant your seedlings at least 24” apart.

Cabbage worms, harlequin bugs, grasshoppers, and other summer insects enjoy eating the thick leaves of collard greens. If you are experiencing pressure from pests, drape light row cover over your collard plants.

Collard leaves can be harvested after they have matured to the size of a large dinner plate. Individual leaves can be harvested throughout the summer, fall, and winter. Leaves are especially tasty and sweet after plants have experienced moderate frost.

Eating and Storing

Some people enjoy eating raw collards, using them like a tortilla or lettuce wrap. Collard greens are traditionally simmered in broth, stock, or fat over low heat.

Collard greens will last 7-10 days in the refrigerator and can be blanched and frozen to store their vegetation throughout the winter.

Saving Seeds

Collards are a biennial plant. Biennials typically do not flower in their first growing season. They must first experience cold weather before they flower, set seed, and die in their second growing season.

When saving seeds from collards, separate varieties by at least 800 feet in their second year. To ensure viable seeds, save seeds from at least five plants. To maintain a variety over time, save seeds from between 20-50 plants.

If your garden does not reach temperatures below 20 °F, you can overwinter collards outside.

When plants cannot be successfully overwintered outside, they can be vernalized in storage. First, take care to dig up the entire plant, roots and all. Then, outer leaves should be trimmed off, with the growing point left intact. Finally, trimmed plants should be replanted into containers filled with slightly moist potting mix or sand for storage.

The optimum storage conditions for Brassica oleracea crops range from 34-39 °F and 80-95% relative humidity. A traditional root cellar is ideal for vernalization but garages, sheds, and other unheated structures can be equally useful in some climates.

In the spring, when the soil can be worked, remove your collards from storage and replant them in your garden, taking care to give them a lot of room to grow. When growing collards for seed, increase spacing to 18-24” apart in rows that are at least 36” apart. Staking the plants is recommended.

After flowering in their second year, harvest collard seeds when they are very hard and pods are dry and brittle. Seeds can be gathered by cutting branches or by harvesting whole plants. Because of this species’ tendency to shatter, the harvested material should be placed on drop cloths or in containers to prevent seed loss.

Brassica oleracea seeds can be threshed by rubbing the pods between one’s hands or against any surface that will cause them to break open. If the pods are dry, they will release their seeds easily when threshed.

Store collard seeds in a cool, dark, and dry place in an airtight container to keep out moisture and humidity. When stored under these conditions, collard seeds can be expected to remain viable for six years.