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Growing Guide: Collards

A pile of leafy greens on a dirt surface

Grow and Save Collard Seeds

How to Grow Collards

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.

Time of Planting

Plants may be transplanted to the garden anytime after the danger of hard frost has passed. Sow seeds indoors, 4-6 weeks before transplanting.

Spacing Requirements

Sow seeds ¼ inch deep. Collards need a lot of space to grow. Plant your seedlings at least 24 inches apart.

Time to Germination

3-10 days

Special Considerations

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.

Common Pests and Diseases

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.

When and How to Harvest for Food Consumption

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.


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.

How to Save Collard Seeds

Collards belong to the Brassica oleracea species, which includes many other crop types, like broccoli, Brussels sprouts, and cauliflower. Because of this, isolation needs to be managed thoughtfully, but because most are biennials that will not flower until their second season, a gardener can grow multiple varieties for eating while simultaneously growing one variety for seed saving.

Life Cycle


Recommended Isolation Distance

Separate varieties by 800 feet – ½ mile mile in their second year of growth.

Recommended Population Sizes

To ensure viable seeds, save seeds from at least 5 plants. When maintaining a variety over many generations, save seeds from 20-50 plants. If you’re saving seeds for genetic preservation of a rare variety, save seeds from 80 plants.


If your garden does not reach temperatures below 20 degrees 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 degrees 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 the 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 inches apart in rows that are at least 36 inches apart. Staking the plants is recommended.

Assessing Seed Maturity

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.

Cleaning and Processing

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.

Storage and Viability

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 6 years.