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.
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.