What to plant in August in Idaho
In Idaho (ID), August sits about 6 weeks before the average first fall frost (September 25). The state averages 138 frost-free days a year (last frost May 10, first frost September 25; USDA zones 3b, 4b, 5b, 6a, 6b, 7a).
19 crops have a sowing or planting window this month, including bok choy / pak choi, borage, dill, fava bean (broad bean), green onion / scallion, kohlrabi - and 15 of those windows close during August.
Dates here come from Idaho frost dates (last frost May 10, first frost Sep 25). For one crop in detail, see when to plant lettuce, spinach or arugula in Idaho.
Idaho 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.
Idaho: planting activity through the year
Last chance in August
Bok Choy / Pak Choi (sow for a fall crop, by Aug 7) · Borage (sow for a fall crop, by Aug 7) · Dill (sow for a fall crop, by Aug 7) · Fava Bean (Broad Bean) (sow for a fall crop, by Aug 7) · Green Onion / Scallion (sow for a fall crop, by Aug 7) · Kohlrabi (sow for a fall crop, by Aug 7) · Lettuce (sow for a fall crop, by Aug 7) · Mache (Corn Salad) (sow for a fall crop, by Aug 7) · Mizuna (sow for a fall crop, by Aug 7) · Rapini (Broccoli Raab) (sow for a fall crop, by Aug 7) · Chervil (sow for a fall crop, by Aug 14) · Mustard Greens (sow for a fall crop, by Aug 14) · Spinach (sow for a fall crop, by Aug 14) · Tatsoi (sow for a fall crop, by Aug 14) · Turnip (sow for a fall crop, by Aug 14)
For fall and winter harvests (18)
Sowings counted back from Idaho'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 |
|---|---|---|---|
| Bok Choy / Pak Choi | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Borage | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Dill | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Fava Bean (Broad Bean) | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Green Onion / Scallion | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Kohlrabi | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Lettuce | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Mache (Corn Salad) | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Mizuna | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Rapini (Broccoli Raab) | Sow for a fall crop | Jul 21 – Aug 7 | Last chance - ends Aug 7 |
| Chervil | Sow for a fall crop | Jul 28 – Aug 14 | Last chance - ends Aug 14 |
| Mustard Greens | Sow for a fall crop | Jul 28 – Aug 14 | Last chance - ends Aug 14 |
| Spinach | Sow for a fall crop | Jul 28 – Aug 14 | Last chance - ends Aug 14 |
| Tatsoi | Sow for a fall crop | Jul 28 – Aug 14 | Last chance - ends Aug 14 |
| Turnip | Sow for a fall crop | Jul 28 – Aug 14 | Last chance - ends Aug 14 |
| Arugula | Sow for a fall crop | Aug 4 – Aug 21 | Aug 4 – Aug 21 |
| Watercress | Sow for a fall crop | Aug 4 – Aug 21 | Aug 4 – Aug 21 |
| Radish | Sow for a fall crop | Aug 11 – Aug 28 | Aug 11 – Aug 28 |
Keep sowing (succession)
Repeat sowings of crops already in the ground, for a steady harvest instead of a glut.
- Amaranth (Leaf): sow again on Aug 9
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 Idaho
Every crop has its own full-year dates for Idaho: indoor start, transplant or direct sowing, and harvest.
Fall garden season: August garden jobs in Idaho
- The average first frost is September 25, about 6 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: bok choy / pak choi, borage, dill, fava bean (broad bean), green onion / scallion, kohlrabi. 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 Idaho
Idaho spans USDA zones 3b, 4b, 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 Idaho in August?
19 crops have a window in August: bok choy / pak choi, borage, dill, fava bean (broad bean), green onion / scallion, kohlrabi, lettuce, mache (corn salad), mizuna, rapini (broccoli raab) and more. The tables above give the exact dates for each.
Is it too late to plant garlic in Idaho in August?
Not too late - it's actually a little early. In Idaho the next garlic window opens around October 6: plant in fall, after first frost.
Is it too late to plant tomatoes in Idaho in August?
For this year, yes - the tomato windows in Idaho have closed. The next step is to start seeds indoors from about March 15.
When is the first frost in Idaho?
The statewide average first fall frost is around September 25 and the last spring frost around May 10. Idaho 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 Idaho in August?
From plantings made on time: radicchio, tarragon, potato, fennel (bulb), mint, lemon balm, cucumber, tomato, sweet corn, sweet marjoram.
What to plant in August in other states
Dates are computed from Idaho’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.