When to plant kale in Enterprise and Joseph, OR

Why frost makes kale sweeter

As temperatures drop, kale converts some of its starch into sugars, which act as a natural antifreeze in its cells. The result is noticeably sweeter, milder leaves after a few frosts. Hardy varieties like Winterbor and Red Russian survive into the low teens or below, and west of the Cascades kale often produces all winter.

Soil and clubroot

Kale grows best in fertile soil with a pH of about 6.0 to 7.5. In the Northwest, the main soil threat is clubroot, a soilborne disease of the whole cabbage family that causes swollen, distorted roots and wilting plants. It thrives in acidic, wet soil, and its spores survive in the ground for many years.

If clubroot has shown up before, raise the pH to about 7.2 with lime at least a month before planting, improve drainage, and don't plant any cabbage-family crops in that spot for several years. Start with clean transplants and don't move soil from infected beds.

Feeding and water

Kale is a leaf crop, so it responds well to nitrogen. Mix compost and a balanced fertilizer into the bed, then side-dress with a little more nitrogen a month or so after planting. Keep the soil evenly moist; drought makes leaves tough and strong-flavored.

Pests

Cabbage aphids form gray, waxy colonies, often under leaves and in the growing tip. Blast them off with water, remove badly infested leaves, and let ladybugs and parasitic wasps do the rest. The green caterpillars are imported cabbageworms, the larvae of the white butterflies seen over gardens in summer. Row cover from planting day keeps the butterflies from laying eggs; Bt, a bacterial spray that affects only caterpillars, controls them if they're already there.

Flowering in spring

Kale is a biennial. After a winter of cold, it flowers the next spring. Before the flowers open, the tender shoots (often sold as kale raab) are sweet and good to eat. Once flowers open, pull the plant and compost it.

Harvest and storage

Pick the lowest, oldest leaves first and leave at least five or six leaves on top so the plant keeps growing. Kale stores best near freezing with high humidity, so keep it bagged in the fridge, where it lasts one to two weeks.