Idaho · zones 5b–7b
When to plant kale in Idaho.
Sow or transplant between Apr 3 to May 1 in a typical year, keyed to Idaho's median last frost around May 11. A second, fall sowing fits Jun 28 to Aug 13. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Kale dates for a typical Idaho season.
1 · Start indoors
Feb 20 to Mar 20
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Apr 3 to May 1
Keyed to the ~May 11 last frost. Sow 0.25" deep, 16" apart.
Fall round
Jun 28 to Aug 13
Counted back from the ~Sep 28 first frost.
Harvest
~45 days later
~2 lb per plant over ~16 weeks.
Idaho spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 7b. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Idaho growing notes
A single kale plant here can give up about 2 pounds of leaf across a season, and Idaho's cool nights are what let one planting keep giving that much for months.
One planting, cut for months instead of resown
Kale goes in as a transplant, spaced about 16 inches apart to give each one room to bush out, and reaches a real harvest in around 45 days. Its yield here runs close to 2 pounds a plant, a figure that reflects a season of repeated cutting rather than one big pull, since this crop is never harvested all at once. Unlike a root crop or a leafy green that gets resown every couple of weeks to keep pace with the calendar, kale goes in once and keeps giving; the plant does the rest of the work across the season.
Both a spring and a fall start work here, so the choice is about preference more than necessity. A spring transplant set out once the soil has warmed keeps producing leaves right through summer and often keeps going after more tender crops nearby have finished for the year, while a transplant set in late summer heat comes into its best condition just as the weather turns and stays productive well into fall.
Cold is this crop's advantage, not its risk
Many gardeners who grow this crop through a cold snap say the leaves taste better afterward than they did before it. The only way to know for a given planting is to taste one leaf ahead of a hard cold night and another the next morning, since the plant itself gives no other visible sign that anything has changed.
That cold tolerance also means kale is one of the last things standing in a garden after the state's first fall frost has ended more tender crops for the year. Zones here run from 5b up through 7b, and an ordinary frost that stops a tomato or a bean cold barely slows this one down, which is why a fall planting often keeps producing well after the calendar most other vegetables are working against has already run out.
Working pest checks into a harvest already underway
Cabbage worms and loopers hide on the underside of the leaf, which happens to be the exact surface already getting checked during a normal cutting round, so scouting folds into harvest instead of becoming a separate chore. Turning each leaf before it goes in the basket catches the small green caterpillars and the pale egg clusters underneath before they turn into a bigger problem two cuttings later. Aphids settle into the tightly ruffled center leaves of the curlier varieties, which is why a hard rinse before cooking matters more on this crop than on flatter greens; the folds hide what a glance misses.
Flea beetles hit hardest right after transplanting, riddling young leaves with small round holes before the plant is established enough to shrug it off. Covering the bed with row fabric for those first two weeks after the transplants go in earns its keep more than covering it any later. Cabbage root maggot works underground instead, attacking the stem and roots of a young transplant in cool, damp spring soil; a simple collar, a few inches of cardboard snugged around the base of the stem at transplanting, blocks the adult fly from laying eggs at the soil line for the cost of a few minutes' work. Black rot announces itself in a V shape, a yellow wedge starting at the leaf edge and pointing back toward the vein, which blackens as the wedge spreads. Any leaf carrying it belongs out of the garden entirely, not in the compost, since this one survives on plant debris and returns the following year if it gets the chance.
In Idaho: watch for
The pests that find kale here.
The short season here, about 140 frost-free days, keeps kale in front of cabbage worms & loopers only briefly. One early row cover usually carries a planting through the worst of it.
Green caterpillars chewing ragged holes; green droppings.
Organic fix: Handpick, cover with netting, spray Bt.
Gray-green clusters tucked into the leaf folds.
Organic fix: Blast with water, then insecticidal soap.
Tiny holes peppering the young leaves.
Organic fix: Row cover from day one; diatomaceous earth.
Black rot
Yellow V-shaped wedges cutting in from the leaf edge, veins blackening inside.
Organic fix: Pull infected plants, water at the base, keep brassicas out of that bed 3 years.
Seedlings wilt, yellow and stall for no reason; white maggots tunnel the roots.
Organic fix: Row cover before the flies are up, when yellow rocket blooms; rotate the bed.
Your season math: Idaho gives kale about 140 frost-free days, and it needs roughly 45 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting kale in Idaho: questions
When should I plant kale in Idaho?+
In a typical Idaho year, sow kale or set out transplants between Apr 3 to May 1, keyed to the state's median last frost around May 11. There's also a fall window: Jun 28 to Aug 13. Your exact dates shift with your ZIP code and microclimate.
When do I start kale seeds indoors in Idaho?+
Start seeds inside about 6 weeks before set-out: roughly Feb 20 to Mar 20 for a typical Idaho season.
What USDA zone is Idaho?+
Idaho spans zones 5b–7b, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many kale plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.