When to Plant Cabbage in Idaho
Published: April 24, 2026
Idaho gardeners in Zone 5a have a 26-week frost-free window for cabbage (April 15 to October 15). Cool-season crops like cabbage do well here because the short, cool summers match the plant's temperature preferences naturally. This guide gives exact dates for Idaho based on your local frost calendar.
Cabbage Planting Dates for Idaho
| Start seeds indoors | February 25–March 4 |
| Last frost (average) | April 15 |
| Transplant outdoors | March 25–April 4 |
| Expect first harvest | May 24 – July 3 |
| Fall crop start | July 23–August 2 |
| Fall harvest | September 21 |
| First fall frost (average) | October 15 |
Dates above assume Zone 5a, the most common zone in Idaho. Gardeners in cooler Coeur d'Alene (Zone 4b) plant 1–2 weeks later; warmer Boise (Zone 5a) can plant 1–2 weeks earlier.
⚠ Start cabbage indoors 6–8 weeks before last frost. Transplant 2–4 weeks before last frost. Very frost tolerant — withstands temperatures as low as 20°F. Also plant in late summer for fall harvest.
Growing Cabbage in Idaho's Climate
Idaho's cold Zone 5a climate is close to ideal for cabbage. 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 cabbage crop in Idaho 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 cabbage pests to watch for in Idaho include Cabbage Worm and Cabbage Looper. The first line of defense is companion planting: Onion and Dill 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.
Cabbage Garden Calendar for Idaho
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| March | Transplant outdoors | Soil temp must be 45°F+; nighttime lows above 50°F |
| April | Harden off seedlings | Set seedlings outdoors 1–2 hours daily, increasing gradually |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | — | Dormant season |
| July | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| August | — | Dormant season |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining cabbage; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Cabbage Growing Tips for Idaho Gardeners
- •Space plants 18 inches apart — crowding reduces head size and promotes fungal disease.
- •Side-dress with nitrogen 3–4 weeks after transplanting to support rapid leaf formation.
- •Idaho'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.
- •Harvest when heads feel firm; leave the root ball in the ground and small secondary heads may form.
Companion Planting for Cabbage in Idaho
In Idaho's cold climate, planting cabbage with Onion and Dill helps deter pests and improve soil. Avoid planting near Tomato and Strawberry, which inhibit cabbage growth through root chemistry or shared pest pressure. See the full cabbage companion planting guide for the complete list.
Cabbage Planting Dates by City in Idaho
Top cities in Idaho — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant cabbage in Idaho?
In Idaho (Zone 5a), start cabbage seeds indoors around February 25–March 4 and transplant outdoors around March 25–April 4 — 3 weeks before the state's average last frost of April 15.
What is the last frost date in Idaho?
Idaho's average last frost date is April 15 in the state's most common Zone 5a. 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 cabbage year-round in Idaho?
cabbage is a cool-season crop in Idaho, 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 cabbage varieties grow best in Idaho?
For Idaho's Zone 5a, consult a local nursery or extension office for cabbage variety recommendations.
When do I start cabbage seeds indoors in Idaho?
Start cabbage seeds indoors in Idaho around February 25–March 4, which is 7 weeks before the state's average last frost of April 15. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.