What to plant in September in Illinois
In Illinois (IL), September sits about 4 weeks before the average first fall frost (October 14). The state averages 177 frost-free days a year (last frost April 20, first frost October 14; USDA zones 5a, 5b, 6a, 6b, 7a).
8 crops have a sowing or planting window this month, including chervil, mustard greens, spinach, tatsoi, turnip, arugula - and 8 of those windows close during September.
Dates here come from Illinois frost dates (last frost Apr 20, first frost Oct 14). For one crop in detail, see when to plant spinach, arugula or radish in Illinois.
Illinois: planting activity through the year
Last chance in September
Chervil (sow for a fall crop, by Sep 2) · Mustard Greens (sow for a fall crop, by Sep 2) · Spinach (sow for a fall crop, by Sep 2) · Tatsoi (sow for a fall crop, by Sep 2) · Turnip (sow for a fall crop, by Sep 2) · Arugula (sow for a fall crop, by Sep 9) · Watercress (sow for a fall crop, by Sep 9) · Radish (sow for a fall crop, by Sep 16)
For fall and winter harvests (8)
Sowings counted back from Illinois'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 |
|---|---|---|---|
| Chervil | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
| Mustard Greens | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
| Spinach | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
| Tatsoi | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
| Turnip | Sow for a fall crop | Aug 16 – Sep 2 | Last chance - ends Sep 2 |
| Arugula | Sow for a fall crop | Aug 23 – Sep 9 | Last chance - ends Sep 9 |
| Watercress | Sow for a fall crop | Aug 23 – Sep 9 | Last chance - ends Sep 9 |
| Radish | Sow for a fall crop | Aug 30 – Sep 16 | Last chance - ends Sep 16 |
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 Illinois
Every crop has its own full-year dates for Illinois: indoor start, transplant or direct sowing, and harvest.
Spring bulbs to plant in September in Illinois
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 Illinois
- The average first frost is October 14, about 4 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: chervil, mustard greens, spinach, tatsoi, turnip, arugula. 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 Illinois
Illinois spans USDA zones 5a, 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 Illinois in September?
8 crops have a window in September: chervil, mustard greens, spinach, tatsoi, turnip, arugula, watercress, radish. The tables above give the exact dates for each.
Is it too late to plant garlic in Illinois in September?
Not too late - it's actually a little early. In Illinois the next garlic window opens around October 25: plant in fall, after first frost.
Is it too late to plant tomatoes in Illinois in September?
For this year, yes - the tomato windows in Illinois have closed. The next step is to start seeds indoors from about February 23.
When is the first frost in Illinois?
The statewide average first fall frost is around October 14 and the last spring frost around April 20. Your town can be a week or two either side - look yours up by ZIP code.
What can I harvest in Illinois in September?
From plantings made on time: leek, salsify, celery, luffa (loofah gourd), peanut, sweet potato, zucchini / summer squash, cucumber, chayote, broccoli.
What to plant in September in other states
Dates are computed from Illinois’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.