Idaho · zones 5b–7b
When to plant bell peppers in Idaho.
Sow or transplant between May 27 to Jul 6 in a typical year, keyed to Idaho's median last frost around May 11. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Bell Peppers dates for a typical Idaho season.
1 · Start indoors
Apr 15 to May 25
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
May 27 to Jul 6
Keyed to the ~May 11 last frost. Sow 0.25" deep, 18" apart.
Harvest
~70 days later
~4 lb per plant over ~8 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
Bell peppers are the slowest crop in an Idaho garden to get moving, and rushing the transplant costs more than waiting a week ever does.
Cold soil, not cold air, is what stalls this crop
A bell pepper transplant set into ground that's still cold will often just sit there, roots barely moving, for two or three weeks before it puts on a single new leaf. That's the test worth running instead of guessing at a soil thermometer reading: if a transplant hasn't grown at all two weeks after going in, the ground is the problem, not the plant. Pulling it and starting over rarely helps; the fix is waiting, or giving the bed a head start with black plastic or a cover that banks heat in the soil before transplanting.
This is also why peppers are worth reserving for the state's warmest ground. A pepper needing about 70 days from transplant looks comfortable against a roughly 140-day frost-free window, but peppers can't use the cold ends of that window, and a slow, cold start in a high-elevation bed cuts it closer than the raw math suggests. Treasure Valley gardens that warm up earlier and hold heat longer into fall are where a full pepper crop comes closest to a sure thing. In the colder 5b and 6a country, the same plant is still workable, but it needs the warmest spot in the yard and no tolerance for a late start.
Phytophthora blight follows standing water, not bad luck
Phytophthora blight is a soil-borne problem, not an airborne one, and it shows up where water sits: a low spot in the row, a bed that drains slowly after a hard watering, the base of a plant set into ground that was mounded flat instead of raised. The plant wilts fast, sometimes overnight, with the stem near the soil line going dark and soft, and by the time the wilting is obvious the root system underneath is usually already gone. There is no rescuing a plant once it collapses this way; the fix lives upstream, in how the bed was built in the first place.
Raised rows or mounded beds that shed water instead of holding it, and drip irrigation that wets the root zone without soaking the whole bed, are what keeps this disease from getting a foothold. At 18 inches between plants, a bed with decent drainage and good airflow does most of the preventive work before a spray comes into it. Bacterial leaf spot is the other disease worth watching for on peppers, and it spreads on wet foliage and on hands or tools that brushed a wet, infected plant before touching a healthy one, so working the patch dry is worth more than it sounds like it should be.
Flea beetles first, aphids all season, and a soil quirk worth knowing
Flea beetles hit peppers earliest, chewing small round shot-holes through leaves on transplants still small enough for the damage to matter; a young plant covered in pinholes is losing leaf area it needs to get established. Row cover over the bed for the first couple of weeks after transplanting keeps the beetles off without a spray, and it can come off once the plants are big enough that a little leaf damage stops mattering. Aphids show up all season on new growth and leaf undersides and are usually a hard water spray away from being a non-issue.
One more thing worth watching: a lot of the state's irrigated ground runs alkaline enough to lock up iron before a plant's roots can take it up. New leaves coming in pale yellow with the veins still green usually means the soil is doing that rather than the plant going hungry, and more fertilizer will not fix it. The ordinary chelated iron on a garden center shelf mostly stops working once soil pH climbs this high; look for one labeled EDDHA, since that form is what still functions on alkaline ground. It is not a disease and not a pest, just a soil quirk worth recognizing before wasting a feeding cycle.
In Idaho: watch for
The pests that find bell peppers here.
The short season here, about 140 frost-free days, keeps pepper, bell in front of aphids only briefly. One early row cover usually carries a planting through the worst of it.
Clusters on new growth, sticky leaves, curling tips. Green peach aphid spreads virus.
Organic fix: Blast with water, then insecticidal soap or neem.
Bacterial leaf spot
Small water-soaked spots that turn brown; badly spotted leaves drop.
Organic fix: Plant resistant varieties, avoid overhead watering, rotate out of nightshades.
Plant wilts and collapses at the soil line after a bed stays soggy.
Organic fix: Plant on raised ground for drainage; remove collapsed plants and do not replant there.
Tiny shot-hole pits peppering young leaves.
Organic fix: Row cover the seedlings; healthy transplants outgrow the damage.
Your season math: Idaho gives bell peppers about 140 frost-free days, and it needs roughly 70 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting bell peppers in Idaho: questions
When should I plant bell peppers in Idaho?+
In a typical Idaho year, sow bell peppers or set out transplants between May 27 to Jul 6, keyed to the state's median last frost around May 11. Your exact dates shift with your ZIP code and microclimate.
When do I start bell peppers seeds indoors in Idaho?+
Start seeds inside about 6 weeks before set-out: roughly Apr 15 to May 25 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 bell peppers 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.