What to plant in September in Idaho
In Idaho (ID), September sits about 1 week before the average first fall frost (September 25). The state averages 138 frost-free days a year (last frost May 10, first frost September 25; USDA zones 3b, 4b, 5b, 6a, 6b, 7a).
1 crop has a sowing or planting window this month: shallot.
Dates here come from Idaho frost dates (last frost May 10, first frost Sep 25). For one crop in detail, see when to plant tomato, lettuce or garlic in Idaho.
Idaho covers a very wide range of climates, so dates near you can be two weeks or more either side of these. Enter your ZIP code in the planting calendar for dates tuned to your town.
Idaho: planting activity through the year
For fall and winter harvests (1)
Sowings counted back from Idaho's first fall frost, so the crop matures before the cold - or, for garlic and similar, planted after it.
| Crop | What to do | Window | This month |
|---|---|---|---|
| Shallot | Plant in fall (after first frost) | Sep 29 – Oct 16 | Opens Sep 29 |
Harvesting in September
First harvests expected this month from crops sown or planted on time earlier in the season.
Planting dates for popular crops in Idaho
Every crop has its own full-year dates for Idaho: indoor start, transplant or direct sowing, and harvest.
Spring bulbs to plant in September in Idaho
Tulips, daffodils, hyacinths and crocus are planted in fall, once the soil has cooled and before it freezes. The exact window depends on the state, so our bulb guide quotes what each extension service says.
Fall garden season: September garden jobs in Idaho
- The average first frost is September 25, about 1 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: shallot. Fast greens and radishes are the safest bets this late.
- Row cover buys 4-6°F of frost protection and weeks of extra harvest - see season extension.
- Pull finished crops and sow a cover crop (cereal rye or crimson clover) into empty beds before the soil gets cold.
USDA zone chart for Idaho
Idaho spans USDA zones 3b, 4b, 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average.
Questions gardeners ask
What vegetables can I plant in Idaho in September?
1 crops have a window in September: shallot. The tables above give the exact dates for each.
Is it too late to plant garlic in Idaho in September?
Not too late - it's actually a little early. In Idaho the next garlic window opens around October 6: plant in fall, after first frost.
Is it too late to plant tomatoes in Idaho in September?
For this year, yes - the tomato windows in Idaho have closed. The next step is to start seeds indoors from about March 15.
When is the first frost in Idaho?
The statewide average first fall frost is around September 25 and the last spring frost around May 10. Idaho covers a wide range of climates, so local dates can differ by two weeks or more - look yours up by ZIP code.
What can I harvest in Idaho in September?
From plantings made on time: chili pepper, watermelon, leek, winter squash, zucchini / summer squash, parsnip, cucumber, salsify, pumpkin, broccoli.
What to plant in September in other states
Dates are computed from Idaho’s statewide average frost dates (from NOAA/NCEI climate normals) and each crop’s timing in our crop database. Your garden may be a week or two either side - for dates tuned to your ZIP code, use the planting calendar.