How to Sow
Sowing Seed Indoors:
- Direct sowing is recommended, but to get a head start you can grow collards indoors 3-4 weeks before the last frost
- Sow seeds ¼ - ½ inches deep in seed-starting formula
- Keep the soil moist at 70 degrees F
- Seedlings emerge in 10-21 days
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Sowing Directly in the Garden
- For optimum flavor, grow in cool weather after danger of frost.
- Sow in well-drained soil in full sun.
- In rows 30 inches apart, sow seed directly in the ground ¼- ½ inches deep.
- Seedlings emerge in 10-21 days depending on soil and weather conditions.
- Thin gradually to stand 6-8 inches apart starting when seedlings are about 3 inches high.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. Avoid disturbing the soil around the plants when weeding.
- Keep plants well watered during dry periods to promote rapid, uninterrupted growth. Plants need about 1-1/2 inches of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It’s best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
Harvest and Preserving Tips
- Harvest whole plants when they are 6-8 inches tall.
- If you do not want the whole plant, pick the bottom leaves as you need them and the inner buds will keep producing.
- You can also harvest whole plants by cutting off just below the crown.
- If grown in the fall, wait until after a light frost as the frost sweetens the flavor.
- Wrap the leaves in a clean, wet tea towel, or damp paper towel and place in a perforated plastic bag and refrigerate.
- Collards are best when steamed, sautéed, or boiled.
Common Disease Problems
Alternaria leaf spot: Small, round reddish brown spots with white to gray centers for on the upper surface of the leaves. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Bacterial Leaf Spot: This causes brown water soaked spots on the foliage which eventually makes the foliage turn yellow. It thrives in cooler temperatures. Burpee Recommends: Remove infected plants. Rotate crops with plants in a different family. Avoid overhead watering. Do not work around plants when they are wet.
Clubroot: This causes plants to wilt in patches during the day, stunts their growth, and causes swollen or disfigured roots. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Improve drainage by reducing soil compaction. Do not work around plants when they are wet. Control weeds where the disease can overwinter.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water & rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cabbage Looper: These worms are green with a white stripe on either side, about 1-1.5 inches long. Burpee Recommends: Hand pick. Floating row covers can help prevent their laying eggs on the plants.
Flea Beetles: These small hopping beetles feed on plant foliage. Burpee Recommends: Rotate crops with plants in a different plant family. Use floating row covers to prevent damage to young foliage.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Collards FAQs
Can I grow collards in a container? Yes, but only in a large container 24 inches deep and wide. Be sure to use a commercial container mix rather than garden soil.
Why did my collards produce a flower stalk? Collards will bolt, or produce a flower stalk, when the temperatures rise quickly in summer. At this point pull the plants from the ground.
Can collards tolerate frost? Yes collards can tolerate a light frost and the flavor can actually be improved with a light frost.
Can I eat collards raw? Yes, collards may be chopped and used in salads or used in smoothies.
Is a fall or spring crop best for the North? A fall crop is preferred in the north because the light frost can improve the flavor. A spring crop may be cut short if the weather turns hot quickly. But you can always try both and see which works best for you.