How to Grow Kale From Seed

Kale (Brassica oleracea var. acephala) needs cool weather to grow from seed to harvest. It can survive in temperatures as low as 20 degrees Fahrenheit but will start to fizzle out when temperatures top 80 F. Kale thrives in the spring and in fall gardens in cold-winter areas with hot summers. If your winters are mild, grow kale in late fall and winter. Cool summer regions make it possible to grow kale from late spring through summer.

Get a jump on the growing season by starting kale seeds indoors in the spring. Sow the seeds 1/4 inch deep and 1 inch apart in a seed flat filled with seed-starting mix. Prepared seed-starting blends are lightweight and sterile, two factors that help maximize germination success. Maintain soil temperature between 45 and 85 F and water when the top of the soil feels dry under your finger.

For a fall crop, start seeds indoors in the summer. Keep the seedlings in a cool area with temperatures below 80 F. By late summer, the four to six-week-old seedlings will be ready to plant out in the garden. Kale seeds germinate in four to seven days and are ready for harvest about 75 days after germination.

Kale grows best in well-draining soil with high amounts of organic matter mixed in the soil. Remove weeds and add compost or manure to the soil before planting. Use 1 inch of seasoned manure or 2 to 3 inches of plant-based compost. Work it 6 to 8 inches into the soil. For a small garden plot, a garden fork does the job well. For larger gardens, renting or investing in a tiller saves time and effort.

A pH between 6.0 and 7.5 is ideal for kale plants. Grow kale in a sunny spot where it gets at least six hours of direct sun per day.

Transplant seedlings outdoors in the spring about four weeks before the last frost date. Kale seedlings can survive a few late spring frosts. Space seedlings 12 inches apart. Leave 18 inches between each row. Plant seedlings so the top of the root mass is level with the soil. Water the soil 1 inch deep after transplanting kale seedlings.

For a fall crop, transplant kale seedlings in late summer, about three months before the first fall frost. In hot summer areas, plant in the fall once daytime temperatures drop below 80 F.

Water once a week during the growing season to keep the soil moist at least 1 inch deep. In wet weather, monitor the soil moisture and water if the top 1 inch starts to dry out. Kale can tolerate drought although it might affect flavor.

Mulch kale seedlings after transplanting them outdoors with 3 to 4 inches of mulch. If you have access to organic chemical-free grass clippings, use them to mulch the kale. Seed-free straw also works well.

Feed kale through the growing season with aged manure or compost. Use 1 cup per plant spread on the soil around the roots. Apply compost after planting when the seedlings grow 6 to 8 inches tall.

Weed around the plants through the growing season to keep the bed free of competition for water and nutrients.

If you prefer to sow seeds directly in the garden, plant kale in late summer, about three months before your typical first winter frost date. Seeds germinate during the remaining warm days and mature for harvest just after the first frosts.

Getting the timing right for direct sowing in spring is tricky as summers tend to heat up before kale has time to mature. For spring growing, grow kale from seed indoors and transplant out. In cool-summer climates, however, you can direct sow kale seeds outdoors as soon as the soil temperature warms to 45 F.