When to Plant Kale in Washington
Published: April 24, 2026
Washington gardeners in Zone 4b have a 21-week frost-free window for kale (May 7 to October 1). Cool-season crops like kale do well here because the short, cool summers match the plant's temperature preferences naturally. This guide gives exact dates for Washington based on your local frost calendar.
Kale Planting Dates for Washington
| Start seeds indoors | April 2–9 |
| Last frost (average) | May 7 |
| Transplant outdoors | April 9–19 |
| Direct sow outdoors | April 9–19 |
| Expect first harvest | June 3 – June 23 |
| Fall crop start | August 6–16 |
| Fall harvest | September 30 |
| First fall frost (average) | October 1 |
⚠ Plant kale 3–5 weeks before last frost for spring. Best planted in late summer (6–8 weeks before first fall frost) for fall/winter harvest. Frost sweetens the flavor.
Growing Kale in Washington's Climate
Washington's cold Zone 4b climate is close to ideal for kale. The cool springs and moderate summers match the plant's natural temperature preferences, producing crisp, sweet, slow-bolting harvests that hot-climate gardeners cannot grow.
The fall kale crop in Washington is often better than the spring crop. Plants mature as temperatures cool in September and October, concentrating sugars and tightening heads or roots. Light frost can improve flavor; hard frost signals harvest time.
Common kale pests to watch for in Washington include Cabbage Worm and Cabbage Looper. The first line of defense is companion planting: Onion and Garlic planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Kale Garden Calendar for Washington
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | — | Dormant season |
| April | Transplant outdoors | Soil temp must be 40°F+; nighttime lows above 50°F |
| May ← | Harden off seedlings | Set seedlings outdoors 1–2 hours daily, increasing gradually |
| June | First harvest window opens | Kale begins producing 55–75 days after transplant |
| July | — | Dormant season |
| August | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining kale; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Kale Growing Tips for Washington Gardeners
- •Harvest outer leaves first using the cut-and-come-again method; the central growing point will produce for months.
- •Kale leaves become sweeter after the first frost as plants convert starches to sugars — wait for cold nights for best flavor.
- •Washington's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Use floating row covers to block cabbage white butterflies from laying eggs on plants.
Companion Planting for Kale in Washington
In Washington's cold climate, planting kale with Onion and Garlic helps deter pests and improve soil. Avoid planting near Tomato and Strawberry, which inhibit kale growth through root chemistry or shared pest pressure. See the full kale companion planting guide for the complete list.
Kale Planting Dates by City in Washington
Top cities in Washington — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant kale in Washington?
In Washington (Zone 4b), start kale seeds indoors around April 2–9 and transplant outdoors around April 9–19 — 4 weeks before the state's average last frost of May 7.
What is the last frost date in Washington?
Washington's average last frost date is May 7 in the state's most common Zone 4b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow kale year-round in Washington?
kale is a cool-season crop in Washington, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What kale varieties grow best in Washington?
For Washington's Zone 4b, consult a local nursery or extension office for kale variety recommendations.
When do I start kale seeds indoors in Washington?
Start kale seeds indoors in Washington around April 2–9, which is 5 weeks before the state's average last frost of May 7. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.