My Planting Calendar

What to plant in September in Montana

In Montana (MT), the average first fall frost (September 15) has passed by mid-September. The state averages 123 frost-free days a year (last frost May 15, first frost September 15; USDA zones 3a, 3b, 4a, 4b, 5a, 5b, 6a).

2 crops have a sowing or planting window this month: shallot, garlic.

Dates here come from Montana frost dates (last frost May 15, first frost Sep 15). For one crop in detail, see when to plant garlic, tomato or lettuce in Montana.

After the first frostSow or plant: 2Start indoors: 0Harvesting: 51

Montana 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.

Montana: planting activity through the year

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5
29
65
91
69
34
8
2
2
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JanFebMarAprMayJunJulAugSepOctNovDec
Frost riskFrost-free: May 15 – Sep 15
Bars count the vegetables, herbs and fruit with a sowing or planting window in each month, from the state’s average frost dates. 2 have one in September; the busiest month is May (91).

For fall and winter harvests (2)

Sowings counted back from Montana's first fall frost, so the crop matures before the cold - or, for garlic and similar, planted after it.

CropWhat to doWindowThis month
ShallotPlant in fall (after first frost)Sep 19 – Oct 6Opens Sep 19
GarlicPlant in fall (after first frost)Sep 26 – Oct 13Opens Sep 26

Harvesting in September

First harvests expected this month from crops sown or planted on time earlier in the season.

Cucumber · Aug 2 – Sep 8Lima Bean · Aug 2 – Sep 1Broccoli · Aug 5 – Sep 16Cauliflower · Aug 5 – Sep 21Cabbage · Aug 5 – Oct 1Chili Pepper · Aug 7 – Sep 6Watermelon · Aug 7 – Sep 6Bush Bean · Aug 9 – Sep 5Kale · Aug 9 – Sep 10Leek · Aug 9 – Sep 28Winter Squash · Aug 10 – Sep 9Lettuce · Aug 10 – Sep 26Brussels Sprouts · Aug 14 – Sep 30Bok Choy / Pak Choi · Aug 15 – Sep 16Mizuna · Aug 15 – Sep 11Swiss Chard · Aug 16 – Sep 12Parsnip · Aug 16 – Sep 15Napa Cabbage · Aug 16 – Sep 27Mustard Greens · Aug 17 – Sep 18Fennel (Bulb) · Aug 17 – Sep 28Cilantro / Coriander · Aug 18 – Sep 29Carrot · Aug 19 – Sep 25Radicchio · Aug 19 – Oct 15Salsify · Aug 19 – Sep 28Pumpkin · Aug 20 – Sep 19Dill · Aug 20 – Sep 26Rosemary · Aug 20 – Sep 19Rapini (Broccoli Raab) · Aug 20 – Sep 26Pea · Aug 21 – Sep 22Collard Greens · Aug 21 – Sep 27Tatsoi · Aug 22 – Sep 23Beet · Aug 23 – Sep 29Radish · Aug 23 – Sep 17Celery · Aug 23 – Oct 2Celeriac · Aug 23 – Sep 12Spinach · Aug 24 – Sep 18Arugula · Aug 24 – Sep 20Kohlrabi · Aug 25 – Sep 26Mache (Corn Salad) · Aug 25 – Sep 26Turnip · Aug 27 – Oct 3Chervil · Aug 27 – Oct 3Luffa (Loofah Gourd) · Aug 27 – Oct 26Rutabaga · Aug 28 – Sep 24Peanut · Aug 30 – Oct 19Sweet Potato · Sep 3 – Oct 3Borage · Sep 4 – Oct 11Parsley · Sep 5 – Oct 12Green Onion / Scallion · Sep 9 – Oct 16Watercress · Sep 13 – Oct 10Endive & Escarole · Sep 20 – Oct 22Fava Bean (Broad Bean) · Sep 24 – Oct 26

Planting dates for popular crops in Montana

Every crop has its own full-year dates for Montana: indoor start, transplant or direct sowing, and harvest.

When to plant garlic in Montana →When to plant tomato in Montana →When to plant lettuce in Montana →When to plant bell pepper in Montana →When to plant carrot in Montana →When to plant onion in Montana →When to plant pea in Montana →When to plant spinach in Montana →Montana frost dates by zone →

Spring bulbs to plant in September in Montana

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.

Bulb planting guide by state, with depth and spacing →When to plant daffodils →When to plant tulips →

After the first frost: September garden jobs in Montana

  1. The average first frost (September 15) has passed - pull frost-killed tender plants and compost the healthy ones; bin or burn anything that had blight or mildew.
  2. Plant garlic now (Sep 26 – Oct 13): single cloves, pointy end up, 2 inches deep and 6 inches apart, then mulch.
  3. Leave cold-hardy roots (carrots, parsnips, leeks) in the ground under a thick mulch and dig them as needed.
  4. Clean and oil tools, drain hoses, and note what worked this year while you still remember - it makes next year's plan far easier.

USDA zone chart for Montana

Montana spans USDA zones 3a, 3b, 4a, 4b, 5a, 5b, 6a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average.

ZoneLast frostFirst frostSeason
Zone 3May 15Sep 15120 days
Zone 4May 10Sep 25135 days
Zone 5Apr 30Oct 5160 days
Zone 6Apr 15Oct 15185 days

Questions gardeners ask

What vegetables can I plant in Montana in September?

2 crops have a window in September: shallot, garlic. The tables above give the exact dates for each.

Is it too late to plant garlic in Montana in September?

No - plant in fall (after first frost) runs Sep 26 – Oct 13 in Montana.

Is it too late to plant tomatoes in Montana in September?

For this year, yes - the tomato windows in Montana have closed. The next step is to start seeds indoors from about March 20.

When is the first frost in Montana?

The statewide average first fall frost is around September 15 and the last spring frost around May 15. Montana 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 Montana in September?

From plantings made on time: cucumber, lima bean, broccoli, cauliflower, cabbage, chili pepper, watermelon, bush bean, kale, leek.

← August in MontanaOctober in Montana →Full-year Montana planting calendar →Montana frost dates →

What to plant in September in other states

ColoradoIdahoNevadaUtahWyomingAlabamaAlaskaArizonaAll states →

Dates are computed from Montana’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.