What to Plant in August: Zone-by-Zone Fall Garden Guide
Updated July 2026 · SowWhen
The short answer: in August, almost every US gardener can still plant something — but what that something is depends entirely on your USDA zone. In zones 3–4, August is last call for the quickest greens and, surprisingly, the first call for garlic. In zones 5–6 it is the busiest fall-sowing month of the whole year. In zones 7–8 it is brassica month — broccoli, kale, and collards go in now. And in zones 9–10 it is a preparation month, because the real fall planting starts in September. Below is the zone-by-zone breakdown, with every window computed from that zone's average first fall frost — the same math the SowWhen calendar runs for your exact zone.
Why August planting is counted backward
Spring planting counts forward from the last frost; fall planting counts backward from the first one. A fall crop needs enough frost-free days left to reach maturity, plus a cushion because plants grow more slowly as days shorten. So the question 'can I still sow carrots?' is really 'is my first fall frost at least 8–10 weeks away?' — and the answer flips from zone to zone. That is why zone 3 gardeners are finishing their fall sowing in early August while zone 8 gardeners have barely started. All dates below are zone averages; your frost dates are probabilities, not promises, so treat each window as a target, not a deadline to the day.
Zones 3–4: last call for greens — and time to think about garlic
With a first fall frost around September 8–12 (zone 3) and September 18–22 (zone 4), the fall window here is nearly shut, so the first week or two of August is a sow-it-now moment. In zone 3a, spinach, mustard greens, bok choy, and cilantro can go in until about August 4, and the two fastest crops — radishes and arugula — until about August 11. Zone 3b gets a few extra days on all of those, plus lettuce, turnips, kohlrabi, and dill through the first day or so of the month.
Zone 4 has more breathing room: lettuce, turnips, and kohlrabi sow until roughly August 7 (4a) or August 11 (4b); spinach, mustard, bok choy, and cilantro until mid-month; and radishes and arugula until August 21–25. A radish sown in early August is on your plate before month's end, and arugula follows about a week later — these are the two crops to reach for if you are reading this late.
The northern consolation prize is garlic. Zone 3 plants cloves from about August 11–25 (3a) or August 15–29 (3b), and zone 4a from August 21 — several weeks before the ground starts to freeze, so the cloves can root before winter. Plant now, mulch well, and harvest next summer. It is the single best 'last thing in the ground' for a short-season garden.
Zone 5: the fall-sowing window opens this week
Zone 5's first fall frost lands around October 1–5, which makes early August the hinge of the fall garden. The first week of the month is last call for the slower crops: carrots, beets, and bulb fennel need to be in by about August 6 (5a) or August 10 (5b), and the same dates close the direct-sow window for kale and collard greens. Miss those by a week and the crop may still limp in — miss them by three and it will not.
Then, from August 6–10 onward, nearly everything quick opens at once: lettuce, spinach, cilantro, turnips, kohlrabi, mustard greens, bok choy, and dill all sow from early-to-mid August into late August, and radishes and arugula run all the way into the first week of September. Cool-season flowers join them — calendula and cornflower both take an August sowing in zone 5 for fall color. If you only garden one weekend this month, make it the second weekend of August.
Zone 6: brassicas first, roots mid-month, greens late
Zone 6 (first frost around October 17–25) runs on a three-part August schedule. First, the broccoli window is closing: fall broccoli goes in by about August 1 in 6a and August 9 in 6b — this is the week, not the month, to act. Kale and collards are more forgiving, sowing from late July clear through August 22 (6a) or August 30 (6b).
Second, mid-month belongs to the roots: carrots, beets, and fennel sow from about August 8–22 in 6a, or August 16–30 in 6b. Fall carrots are worth the effort — roots that mature into cooling October soil come out sweeter than any spring crop. Third, from August 22 (6a) or August 30 (6b), the quick greens open — lettuce, spinach, turnips, kohlrabi, mustard, bok choy, radishes, arugula — and carry your sowing into September.
Zone 7: broccoli's big month
With frost holding off until early-to-mid November, zone 7's August is all about the fall brassicas. Broccoli transplants or seed go in from about July 27 to August 17 in 7a, and August 4–25 in 7b — squarely an August job in both halves. Kale and collard greens follow from August 10 (7a) or August 18 (7b) and stay open into early September; both actually improve after the first light frosts, when cold sweetens the leaves.
In 7a, the tail end of the month adds the roots: carrots, beets, and fennel open around August 24 and run into early September. In 7b, hold those — and the quick salad greens — for September; sowing lettuce into an August heat wave in zone 7 mostly grows regret. If your beds are empty in the meantime, that is normal here: August in zone 7 is two or three deliberate plantings, not a full-garden reset.
Zone 8: begin the fall garden now, sow the rest next month
Zone 8's frost does not arrive until late November, which pushes most fall sowing into September and October — but broccoli starts now: about August 12 to September 2 in 8a, and August 19 to September 9 in 8b. In 8a, kale and collards follow from August 26. Getting brassica seedlings through a zone 8 August takes some shade cloth and evening water, but plants established now will crop from mid-fall onward.
Everything else — the lettuces, roots, and Asian greens — waits for September, when soil temperatures come off their peak. Use August to clear spent spring beds, work in compost, and start brassica seed in trays somewhere cooler than the open garden.
Zones 9–10: the patience month
It feels backwards, but the hottest zones have the least to plant in August. With first frost in December (or effectively never), the fall windows here open from late August at the earliest — broccoli from about August 29 in 9a — and mostly through September and October. In zones 9–10, cool-season crops are fall-through-spring crops: the season you are preparing for is the best gardening weather of your year.
So August is a working month, not a sowing month: pull exhausted spring plantings, refresh beds, order seed while varieties are in stock, and late in the month start broccoli and other brassicas in trays in a bright, shaded spot. Check your zone's calendar toward the end of the month — the windows come fast once the anniversary of the heat breaking arrives.
How to germinate fall seeds in August heat
The universal catch with fall sowing is that cool-season seed must germinate in the year's hottest soil. Three fixes cover most failures: sow slightly deeper than the spring depth, where soil is cooler and moister; keep the seedbed constantly damp, watering in the evening so it stays wet overnight; and shade the row until seedlings emerge — a board laid over the row, a scrap of row cover, or the shadow of a taller neighbor all work. Lettuce is the fussiest of the group (it can refuse to germinate outright in soil above about 80°F), which is one more reason its August windows skew to the cooler zones.
What it's too late for
Everywhere with a real fall frost — zones 3 through 8 — August is too late to start the tender, long-season crops. A tomato, pepper, melon, or winter squash planted now needs 75–100 frost-free days it is not going to get; those are next spring's projects. The honest August garden is a cool-season garden, and that is no consolation prize: frost-sweetened carrots, kale, and collards are some of the best eating of the year.
Every date in this guide is a zone-average window — the same windows SowWhen computes when you open your zone's calendar, which also shows the exact dates for your half-zone rather than the band summaries above. For the fuller method behind the fall garden, read Plan a Second Harvest: The Fall Vegetable Garden, and if you want a steady supply rather than one flush, succession planting shows how to stagger the sowings you make this month.
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