If you don’t live in the south, you probably don’t see collard greens very often, although they are becoming increasingly popular in other parts of the country.
So when to harvest collard greens? They are a leafy, cool-weather vegetable that is perfect for cooking.
However, collard greens can be made more and more throughout the country. A relative of cabbage, broccoli, hugger kale, kohlrabi, and collard greens, this upright, dark green waxy plant is a bit like a head of cabbage.
It is one of the most cold-tolerant of all vegetables, able to withstand temperatures as low as 10+°F. In zone 8 to the south, collard greens usually provide a bumper crop throughout the winter.
You can grow them in the spring and fall, although collard greens grown in the garden in the fall is more popular because the leaves are sweeter when kissed under frost.
Plant collard greens in the spring, 3 to 4 weeks before the last frost. These plants will grow well in raised beds, containers, and in-ground gardens.
Space plants 18 to 24 inches apart in an area with full sun, rich, well-drained soil, and a pH of 6.5 to 6.8.
Improve the native soil by mixing in a few inches of compost or other rich organic matter.
An even amount of water makes the best scattered-leaf glycines. Make sure you add 1 to 1.5 inches of water to them each week.
Collard greens are fast-growing crops and producers, so they must be fed a water-soluble plant food regularly.
Add 3 inches of organic material mulch to keep the soil moist and to keep weeds at bay.
Harvest young collard greens leave when dark green and 10 inches long.
collard greens can be harvested once they reach a usable size. They will be most flavorful when they are young-less than 10 inches long and dark green. Older leaves will be tough and silky.
Scattered-leaf collard greens vegetables are ready to harvest 75 to 85 days from transplanting and 85 to 95 days from seed.
WHEN TO HARVEST COLLARD GREENS
Loose-leaf collard greens are most delicious in cool weather. If harvested after a frost, the leaves will be sweeter; cooler temperatures cause the carbohydrates in the leaves to convert to sugar.
In mild winter areas, collard greens will produce new leaves almost all winter. In areas with heavy icing, protect collars from temperatures as low as 20°F-use row covers, plastic channels, or cold frames.
When temperatures are expected to be in the teens, cover plants with collard greens to prevent the leaves from freezing. Frozen leaves can still be cooked.
Overwintered collard greens will bolster and bloom in the spring. The plants should then be removed and replaced.
If a heatwave hits in the summer, collard greens that are sown in the spring and grow into the summer will be very bitter. However, when the temperature cools again, the new leaves produced in the fall will be delicious.
The roots of summer-grown collard greens are well mulched and watered for optimum flavor.
HOW TO HARVEST COLLARD GREENS
First harvest the leaves from low on the stem, then grow them up the stem. Pick leaves from the outside of the plant and work your way inward. Be careful not to damage the stem where the new leaves emerge.
The leaves will fall off the stem with a sharp downward pull. You can also use a sharp knife.
Leave at least four leaves at the top of the plant (the growing canopy); this will allow the plant to grow new leaves for future harvesting.
Regular harvesting and even watering will allow the plant to produce new young leaves.
HOW TO STORE COLLARD GREENS
After harvesting collard greens, wash the leaves thoroughly to remove any soil that may have clung to the underside of the leaves.
Place the rolled leaves in the refrigerator for a few days to a week. Place the leaves in a perforated plastic bag wrapped in a damp paper towel in a vegetable crisper in the refrigerator to keep the leaves moist and avoid drying out.
Collard greens vegetables can be stored for two to three weeks at 32° to 34°F and 90% to 95% humidity (moist) with some air circulation.
By placing the roots in moist soil or sand, you can harvest the entire collard greens plant and keep the leaves fresh indoors for several weeks.
If you cook the whole collard greens, the stems will become tender.
CONTAMINATED COLLARD GREENS?
I often need to protect cauliflower from cabbage worms and must also watch out for aphids on Brussels sprouts and collard greens, but these pests rarely take the slightest interest in collard greens.
So it bothers me that commercial growers in the U.S. feel the need to use persistent systemic pesticides when growing collard greens, but it’s true.
In 2013, the Environmental Working Group put collard greens and kale on its “dirty list” after finding that the leaves were contaminated with “pesticides that are particularly toxic to the nervous system. This is a very good reason to grow or buy your own organic food.