When to Harvest Kale:
Harvest kale as soon as the leaves are large enough to eat. Pick large, outside kale leaves first; leave the center ones to grow on.
Regular harvest and even watering will keep kale plants producing new tender leaves for several months—as long as the weather stays cool.
Kale leaves will be sweeter if harvested after frost; cool temperatures cause carbohydrates in the leaves to turn to sugar.
Kale is ready for harvest 55 to 75 days from seed sowing. It is best grown to mature in spring or fall before temperatures climb into the 70°sF (21°+C). In mild-winter regions, kale will produce new leaves nearly all winter.
Kale can survive but not thrive where winters are cold; plants can withstand temperatures as low as 14°F (-10°C).
In hard freeze regions, grow kale under row covers, plastic tunnels, or in cold frames. When temperatures in the teens are predicted, cover plants to keep the leaves from freezing. Still, frozen leaves can be cooked.
Kale planted in the spring and grown into the summer will be bitter if hit by summer heat. When summer comes keep roots cool by mulching around plants and make sure plants are well watered; these efforts will improve flavor.
How to Harvest Kale:
Cut kale leaves one-by-one as needed with a garden scissors or knife or cut away the whole head. If you cut kale leaves as needed (called cut-and-come-again) new leaves will grow from the center of the plant.
After harvesting kale, wash the leaves thoroughly to remove any soil that may be clinging to the leaves.
How to Store Kale:
Kale will store for two to three weeks at 32° to 34°F (0°-4°C) and 90 to 95 percent humidity (moist) with some air circulation. Wrap leaves in a moist cloth or paper towel and place them in a perforated plastic bag in the vegetable crisper of the refrigerator; this will keep leaves from drying.
If you cook the whole leaf, the stems will become tender.
More tips: How to Grow Kale.