What to plant in August in Colorado
In Colorado (CO), August sits about 7 weeks before the average first fall frost (October 1). The state averages 149 frost-free days a year (last frost May 5, first frost October 1; USDA zones 3b, 4b, 5a, 5b, 6a, 7a).
22 crops have a sowing or planting window this month, including beet, cilantro / coriander, bok choy / pak choi, borage, dill, fava bean (broad bean) - and 12 of those windows close during August.
Dates here come from Colorado frost dates (last frost May 5, first frost Oct 1). For one crop in detail, see when to plant beet, lettuce or spinach in Colorado.
Colorado 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.
Colorado: planting activity through the year
Last chance in August
Beet (sow for a fall crop, by Aug 6) · Cilantro / Coriander (sow for a fall crop, by Aug 6) · Bok Choy / Pak Choi (sow for a fall crop, by Aug 13) · Borage (sow for a fall crop, by Aug 13) · Dill (sow for a fall crop, by Aug 13) · Fava Bean (Broad Bean) (sow for a fall crop, by Aug 13) · Green Onion / Scallion (sow for a fall crop, by Aug 13) · Kohlrabi (sow for a fall crop, by Aug 13) · Lettuce (sow for a fall crop, by Aug 13) · Mache (Corn Salad) (sow for a fall crop, by Aug 13) · Mizuna (sow for a fall crop, by Aug 13) · Rapini (Broccoli Raab) (sow for a fall crop, by Aug 13)
For fall and winter harvests (20)
Sowings counted back from Colorado'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 |
|---|---|---|---|
| Beet | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Cilantro / Coriander | Sow for a fall crop | Jul 20 – Aug 6 | Last chance - ends Aug 6 |
| Bok Choy / Pak Choi | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Borage | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Dill | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Fava Bean (Broad Bean) | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Green Onion / Scallion | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Kohlrabi | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Lettuce | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Mache (Corn Salad) | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Mizuna | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Rapini (Broccoli Raab) | Sow for a fall crop | Jul 27 – Aug 13 | Last chance - ends Aug 13 |
| Chervil | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Mustard Greens | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Spinach | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Tatsoi | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Turnip | Sow for a fall crop | Aug 3 – Aug 20 | Aug 3 – Aug 20 |
| Arugula | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Watercress | Sow for a fall crop | Aug 10 – Aug 27 | Aug 10 – Aug 27 |
| Radish | Sow for a fall crop | Aug 17 – Sep 3 | Opens Aug 17 |
Keep sowing (succession)
Repeat sowings of crops already in the ground, for a steady harvest instead of a glut.
- Basil: sow again on Aug 11
- Amaranth (Leaf): sow again on Aug 4 and Aug 18
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 Colorado
Every crop has its own full-year dates for Colorado: indoor start, transplant or direct sowing, and harvest.
Fall garden season: August garden jobs in Colorado
- The average first frost is October 1, about 7 weeks away. Pick tender crops (tomatoes, peppers, squash, beans) before it, or cover them on cold nights.
- Still time to sow or plant: beet, cilantro / coriander, bok choy / pak choi, borage, dill, fava bean (broad bean). 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 Colorado
Colorado spans USDA zones 3b, 4b, 5a, 5b, 6a, 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 Colorado in August?
22 crops have a window in August: beet, cilantro / coriander, bok choy / pak choi, borage, dill, fava bean (broad bean), green onion / scallion, kohlrabi, lettuce, mache (corn salad) and more. The tables above give the exact dates for each.
Is it too late to plant garlic in Colorado in August?
Not too late - it's actually a little early. In Colorado the next garlic window opens around October 12: plant in fall, after first frost.
Is it too late to plant tomatoes in Colorado in August?
For this year, yes - the tomato windows in Colorado have closed. The next step is to start seeds indoors from about March 10.
When is the first frost in Colorado?
The statewide average first fall frost is around October 1 and the last spring frost around May 5. Colorado 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 Colorado in August?
From plantings made on time: potato, tomato, sweet corn, onion, shallot, bitter melon, bell pepper, southern pea (cowpea), thyme, sage.
What to plant in August in other states
Dates are computed from Colorado’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.