What to plant in September in Wisconsin
In Wisconsin (WI), September sits about 2 weeks before the average first fall frost (September 30). The state averages 143 frost-free days a year (last frost May 10, first frost September 30; USDA zones 3b, 4a, 4b, 5a, 5b).
1 crop has a sowing or planting window this month: radish - and 1 of those windows close during September.
Dates here come from Wisconsin frost dates (last frost May 10, first frost Sep 30). For one crop in detail, see when to plant radish, tomato or lettuce in Wisconsin.
Wisconsin: planting activity through the year
Last chance in September
Radish (sow for a fall crop, by Sep 2)
For fall and winter harvests (1)
Sowings counted back from Wisconsin'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 |
|---|---|---|---|
| Radish | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
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 Wisconsin
Every crop has its own full-year dates for Wisconsin: indoor start, transplant or direct sowing, and harvest.
Spring bulbs to plant in September in Wisconsin
Plant when the ground cools to about 50-55°F or lower (but is not frozen), and keep planting until a couple of weeks before the ground freezes. (University of Wisconsin Extension) ↗
Fall garden season: September garden jobs in Wisconsin
- The average first frost is September 30, about 2 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: radish. 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 Wisconsin
Wisconsin spans USDA zones 3b, 4a, 4b, 5a, 5b. 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 Wisconsin in September?
1 crops have a window in September: radish. The tables above give the exact dates for each.
Is it too late to plant garlic in Wisconsin in September?
Not too late - it's actually a little early. In Wisconsin the next garlic window opens around October 11: plant in fall, after first frost.
Is it too late to plant tomatoes in Wisconsin in September?
For this year, yes - the tomato windows in Wisconsin have closed. The next step is to start seeds indoors from about March 15.
When is the first frost in Wisconsin?
The statewide average first fall frost is around September 30 and the last spring frost around May 10. Your town can be a week or two either side - look yours up by ZIP code.
What can I harvest in Wisconsin in September?
From plantings made on time: chili pepper, watermelon, leek, winter squash, parsnip, zucchini / summer squash, salsify, pumpkin, rosemary, cucumber.
When should I plant spring bulbs in Wisconsin?
Plant when the ground cools to about 50-55°F or lower (but is not frozen), and keep planting until a couple of weeks before the ground freezes. (University of Wisconsin Extension). See the bulb planting guide for depth and spacing.
What to plant in September in other states
Dates are computed from Wisconsin’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.