Kale

Spring crop: sow or set out transplants four to five weeks before your last frost

Start seeds indoors about four weeks before you plan to set them out, or direct-sow as soon as the soil is workable. Set transplants out four to five weeks before your average last frost date, spacing plants 12 inches apart in rows 2 feet apart. Harden seedlings off by reducing water and temperature for two to three days before transplanting. Kale grows best when temperatures do not exceed 75F, so the spring crop has to size up before summer heat arrives - high summer temperatures reduce growth and cause bitter, off flavors to develop.

Fall crop: sow in midsummer for the best kale of the year

Direct-sow about three months before your average first frost date, or start seedlings indoors in June to transplant out in midsummer. For a later fall crop choose an early variety and count back 50 to 75 days from when you want to start cutting. Kale keeps growing well past the first fall frosts and its flavor improves as temperatures drop, so a midsummer sowing lands the harvest in exactly the weather this crop was built for.

Side-dress nitrogen four weeks after transplanting

About four weeks after transplanting or thinning, side-dress with half a cup of 21-0-0 per 10 feet of row, placed in a band six inches out from the plants, scratched in and watered. Repeat the same side-dress on your fall planting four weeks after it goes in. You are harvesting leaves, not fruit, so nitrogen is the crop - a plant that runs short mid-season puts out small, pale leaves and stops replacing what you cut.

⚠ Keep granular fertilizer off the leaves and six inches away from stems; concentrated nitrogen against wet foliage or crowns will burn them.

Cabbageworms: Bt kurstaki while the caterpillars are still small

Watch weekly for small white butterflies over the bed, pale eggs laid singly on the leaves, ragged holes between the veins, and green frass pellets. When you find young larvae, spray Bacillus thuringiensis var. kurstaki, covering leaf undersides, and repeat as new larvae appear. Brassica leaves shed water, so add a spreader-sticker to the tank. Bt has to be eaten to work and only kills small early-instar larvae, so it succeeds or fails on timing - a caterpillar found at full size has already done its damage and will shrug the spray off.

⚠ Bt kurstaki carries a 0-day pre-harvest interval and a 4-hour re-entry interval on cole crops; its label strongly recommends an approved spreader-sticker.

Cabbage aphids: check the growing tips weekly once nights cool

Scout weekly and treat if more than 10 percent of plants carry aphids. Look at the youngest leaves and growing tips and at the undersides of older leaves, where the gray-green colonies pack in. Spray insecticidal soap or a horticultural oil with a spreader-sticker at high pressure aimed up into the undersides, and pull heavily infested plants rather than trying to rescue them. Cabbage aphids reproduce fastest between 50 and 68F and stall above 95F, so a fall kale planting sits inside their ideal range for months and colonies explode - and once they are wedged into the crown, no spray reaches them.

⚠ Soaps can burn foliage at high concentrations - use the lower labeled rate and avoid spraying in hot sun.

Floating row cover from the day you plant

Lay floating row cover or fine mesh netting over the bed the day you sow or transplant, and secure the edges to the soil so butterflies cannot get underneath to lay eggs. Because kale is harvested as leaves and needs no pollination, the cover can stay on right through to harvest - just lift it when you need to weed or cut. If you skip the cover, scout for tiny, pale, individually-laid eggs on the leaves and crush them by hand. Cabbage white butterflies have to land on the plant to lay their eggs, so fine mesh netting used as a physical barrier keeps the adults off the crop entirely and stops the infestation before there is anything to spray.

Low tunnel to carry kale through winter

Before hard freezes arrive, set hoops over the row and pull a 10 to 14 foot row cover blanket over them, secured taut with bricks, rocks or sandbags. Row cover gives protection down to roughly 24 to 28F depending on grade; add a second layer or a 4- to 6-mil plastic layer over it for colder nights. Vent by clipping or raising the sides on warm days so the tunnel does not cook. Kale is hardy enough to keep standing through winter under cover, and greens matured in cold weather are the sweetest of the year - the limit is not the plant's toughness but the handful of nights that go below what bare foliage tolerates.

Cut the outer leaves and let the crown keep going

Cut baby greens about 20 to 30 days after sowing, or full-size leaves at 50 to 75 days depending on variety. Strip the older, lower leaves first and leave the growing tip alone - the plant keeps producing from the center for months. Fresh leaves hold about a week in the refrigerator. Cut a spring crop before the weather turns hot and dry. Kale grows from a central crown, so removing the oldest outer leaves takes the ones already past their peak while leaving the factory intact; taking the whole top ends the harvest.