What to plant in September in Iowa
In Iowa (IA), September sits about 3 weeks before the average first fall frost (October 8). The state averages 166 frost-free days a year (last frost April 25, first frost October 8; USDA zones 4b, 5a, 5b).
3 crops have a sowing or planting window this month: arugula, watercress, radish - and 3 of those windows close during September.
Dates here come from Iowa frost dates (last frost Apr 25, first frost Oct 8). For one crop in detail, see when to plant arugula, radish or tomato in Iowa.
Iowa: planting activity through the year
Last chance in September
Arugula (sow for a fall crop, by Sep 3) · Watercress (sow for a fall crop, by Sep 3) · Radish (sow for a fall crop, by Sep 10)
For fall and winter harvests (3)
Sowings counted back from Iowa'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 |
|---|---|---|---|
| Arugula | Sow for a fall crop | Aug 17 – Sep 3 | Last chance - ends Sep 3 |
| Watercress | Sow for a fall crop | Aug 17 – Sep 3 | Last chance - ends Sep 3 |
| Radish | Sow for a fall crop | Aug 24 – Sep 10 | Last chance - ends Sep 10 |
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 Iowa
Every crop has its own full-year dates for Iowa: indoor start, transplant or direct sowing, and harvest.
Spring bulbs to plant in September in Iowa
October is ideal. September can make tulips send up leaves in fall. Procrastinators can plant as late as December if the ground is not frozen. (Iowa State University Extension) ↗
Fall garden season: September garden jobs in Iowa
- The average first frost is October 8, about 3 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: arugula, watercress, 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 Iowa
Iowa spans USDA zones 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 Iowa in September?
3 crops have a window in September: arugula, watercress, radish. The tables above give the exact dates for each.
Is it too late to plant garlic in Iowa in September?
Not too late - it's actually a little early. In Iowa the next garlic window opens around October 19: plant in fall, after first frost.
Is it too late to plant tomatoes in Iowa in September?
For this year, yes - the tomato windows in Iowa have closed. The next step is to start seeds indoors from about February 28.
When is the first frost in Iowa?
The statewide average first fall frost is around October 8 and the last spring frost around April 25. Your town can be a week or two either side - look yours up by ZIP code.
What can I harvest in Iowa in September?
From plantings made on time: leek, salsify, celery, luffa (loofah gourd), peanut, sweet potato, zucchini / summer squash, cucumber, broccoli, cauliflower.
When should I plant spring bulbs in Iowa?
October is ideal. September can make tulips send up leaves in fall. Procrastinators can plant as late as December if the ground is not frozen. (Iowa State University Extension). See the bulb planting guide for depth and spacing.
What to plant in September in other states
Dates are computed from Iowa’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.