What to plant in August in Iowa
In Iowa (IA), August sits about 8 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).
29 crops have a sowing or planting window this month, including collard greens, endive & escarole, napa cabbage, parsley, pea, swiss chard - and 8 of those windows close during August.
Dates here come from Iowa frost dates (last frost Apr 25, first frost Oct 8). For one crop in detail, see when to plant pea, swiss chard or beet in Iowa.
Iowa: planting activity through the year
Last chance in August
Collard Greens (sow for a fall crop, by Aug 6) · Endive & Escarole (sow for a fall crop, by Aug 6) · Napa Cabbage (sow for a fall crop, by Aug 6) · Parsley (sow for a fall crop, by Aug 6) · Pea (sow for a fall crop, by Aug 6) · Swiss Chard (sow for a fall crop, by Aug 6) · Beet (sow for a fall crop, by Aug 13) · Cilantro / Coriander (sow for a fall crop, by Aug 13)
For fall and winter harvests (26)
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 |
|---|---|---|---|
| Collard Greens | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Endive & Escarole | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Napa Cabbage | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Parsley | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Pea | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Swiss Chard | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Beet | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Cilantro / Coriander | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Bok Choy / Pak Choi | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Borage | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Dill | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Fava Bean (Broad Bean) | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Green Onion / Scallion | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Kohlrabi | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Lettuce | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Mache (Corn Salad) | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Mizuna | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Rapini (Broccoli Raab) | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Chervil | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Mustard Greens | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Spinach | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Tatsoi | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Turnip | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Arugula | Sow for a fall crop | Aug 17 – Sep 3 | Opens Aug 17 |
| Watercress | Sow for a fall crop | Aug 17 – Sep 3 | Opens Aug 17 |
| Radish | Sow for a fall crop | Aug 24 – Sep 10 | Opens Aug 24 |
Keep sowing (succession)
Repeat sowings of crops already in the ground, for a steady harvest instead of a glut.
- Cucumber: sow again on Aug 1
- Basil: sow again on Aug 1 and Aug 22
- Amaranth (Leaf): sow again on Aug 8 and Aug 22
Harvesting in August
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.
Fall garden season: August garden jobs in Iowa
- The average first frost is October 8, about 8 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: collard greens, endive & escarole, napa cabbage, parsley, pea, swiss chard. 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 August?
29 crops have a window in August: collard greens, endive & escarole, napa cabbage, parsley, pea, swiss chard, beet, cilantro / coriander, bok choy / pak choi, borage and more. The tables above give the exact dates for each.
Is it too late to plant garlic in Iowa in August?
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 August?
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 August?
From plantings made on time: potato, sweet corn, onion, shallot, bell pepper, southern pea (cowpea), brussels sprouts, sunflower, lima bean, edamame (soybean).
What to plant in August 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.