When to start kale seeds
Short answer: start kale indoors 4 to 6 weeks before transplanting and plant it out about 4 weeks before your last frost, or sow it directly as soon as the soil can be worked. Kale is one of the most cold-tolerant crops you can grow.
At a glance
- Start indoors
- 4–6 weeks before setting out (UNH; Iowa State); UMN says about 4 weeks
- Set out
- About 4 weeks before last frost (UNH)
- Germination temperature
- 65–70°F (Iowa State)
- Days to sprout
- 4–7 days (Iowa State)
- Direct sow?
- Yes, as soon as the soil is workable; again about 3 months before first fall frost (UMN)
UNH = University of New Hampshire Extension; UMN = University of Minnesota Extension; Harrington = J. F. Harrington's germination data as published by Oregon State University Extension. Full links are under Sources below.
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How many weeks before the last frost?
University of New Hampshire Extension gives kale 4 to 6 weeks from seed to transplant and says it is safe to set out 4 weeks before the last frost. With an average last frost of May 10, you would sow indoors March 1 to March 15 and set plants out April 12.
University of Minnesota Extension suggests sowing indoors in early April in Minnesota, about four weeks before transplanting. Kale doesn't need a long indoor period, so don't start it with your peppers.
Germination
Iowa State Extension lists 65–70°F for kale germination, with seedlings in 4 to 7 days, and notes the seed germinates in darkness, so cover it. Outdoors, UMN plants seeds a quarter to a half inch deep. Kale is the same species as broccoli, cabbage and cauliflower (UMN). Those crops are grown at room temperature without a heat mat, and kale is no different.
Direct sowing
Direct sowing works well. UMN advises sowing in spring as soon as the soil is workable, in rows 18 to 30 inches apart, and thinning seedlings to 8 to 12 inches apart once they emerge. For baby leaves only, plants can be as close as 4 inches.
Hardening off and transplanting
UMN's kale guidance is simple: harden seedlings by reducing water and temperature for two to three days before transplanting, then set them 8 inches apart in rows 18 inches apart. A gradual week outdoors also works if you have time.
Fall and winter kale
Kale often tastes best in fall. UMN suggests direct seeding again about three months before the average first fall frost, or starting fall transplants indoors in June. Kale and collards keep growing well past the first fall frosts, and UMN notes you can harvest and cook the leaves even after they have frozen. The fall planting calculator works out a sow-by date from your variety's days to maturity.
Soil, feeding and rotation
UMN recommends a soil test, a pH of 6.0 to 7.5, and loamy, well-drained soil with plenty of organic matter. When plants are about four inches tall, side-dress with fertilizer; UMN gives example rates per 100 feet of row, and the fertilizer calculator converts a nitrogen rate into the amount of product. Grow kale where you haven't grown cabbage, cauliflower, broccoli, Brussels sprouts, collards, kale, mustard, turnip or rutabaga for four years. UMN also notes that overheated or water-stressed plants develop pungent or bitter flavors, so keep them watered.
Common mistakes
- Starting too early indoors. Four to six weeks is plenty.
- Waiting for warm weather. Kale goes out weeks before the last frost.
- Skipping the fall crop. Cool fall weather gives the best leaves.
- Letting plants dry out. Water stress makes leaves bitter.
Example schedules
The same timing rules applied to three different average last frost dates. Find your own date on the frost dates page, or check your zone planting calendar for typical ranges.
| Last frost | Start indoors | Plant out | Direct sow |
|---|---|---|---|
| Mar 15 | Jan 4–Jan 18 | Feb 15 | — |
| Apr 15 | Feb 4–Feb 18 | Mar 18 | — |
| May 15 | Mar 6–Mar 20 | Apr 17 | — |
Supplies
Optional. You can start seeds with very little gear; these are the items that make the steps above easier. Disclosure: some links on this site may be affiliate links; if you buy through them we may earn a commission at no extra cost to you. Learn more.
- Kale seed (curly, lacinato or Siberian types): grow a spring and a fall planting.
- Insect-barrier row cover: protects young brassicas.
- Soil test kit: UMN recommends testing before fertilizing.
Frequently asked questions
How early can I plant kale outside?
UNH Extension says kale transplants are safe to set out about 4 weeks before your average last frost. UMN direct sows as soon as the soil is workable.
Can kale survive frost?
Yes. UMN says kale and collards keep producing well beyond the first fall frosts, and the leaves can be harvested and cooked even after freezing.
When do I plant kale for fall?
UMN direct seeds about three months before the average first fall frost, or starts transplants indoors in June.
Sources
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden
- Iowa State University Extension — Germination Requirements for Annuals and Vegetables
- University of Minnesota Extension — Growing collards and kale in home gardens
Dates in the calculator and example tables use the University of New Hampshire Extension timings. Average frost dates are not guarantees; check the forecast before setting out tender plants. Last reviewed 2026-10-23. Found an error? Tell us.