August · USDA Zone 4
summerWhat to plant in August in USDA zone 4
Summer planting guide for zone 4 (Northern Maine, northern Wisconsin, Montana, parts of New England) — a 125-day growing season with last frost around mid-May and first frost around mid-September.
Sow outdoors in August — zone 4
Direct-sow these seeds into prepared garden beds or large containers. Soil temperature matters more than the calendar date — wait for a sustained warm-up before sowing tender crops.
- Fall salad, spinach, kale, radishes, turnips, lettuce
Transplant in August — zone 4
Move hardened-off seedlings into the garden. Tender crops want soil above 16 °C and night temperatures consistently above 10 °C; cool-season transplants tolerate light frost.
- Fall brassicas (broccoli, cabbage, cauliflower)
Harvest in August — zone 4
These crops should be ready or in active harvest in August for zone 4 gardens. Pick fruiting crops every 2-3 days to keep production going.
- Tomatoes, peppers, beans, squash, corn, herbs, onions
Prep and planning — zone 4
- Order garlic for September-October planting
Universal August tasks
These apply across most US and UK gardens in August, regardless of zone.
- Sow autumn salad, spinach, kale, and oriental greens.
- Transplant fall brassicas (broccoli, cabbage, cauliflower) in zones 4-7.
- Preserve the summer harvest — can, freeze, dehydrate, or ferment.
- Order garlic and shallots for fall planting.
- Water consistently — uneven moisture splits tomatoes and bolts greens.
- Cut and dry herbs at peak flavor (just before flowering).
Why this works for zone 4
Zone 4 has average annual minimum temperatures of -30 to -20°F (-34 to -29°C) and a frost-free window from mid-May to mid-September — about 125 growing days. Tomatoes and peppers benefit from row covers in early season. Mulch heavily over winter for perennials and garlic.
Dates are zone-wide averages. Local microclimates (south-facing slopes, urban heat, lakeside warmth, elevation) can shift the window by 1-2 weeks within the same zone.
UK gardeners — August
August is harvest peak and the gateway to autumn. Sow spring cabbage, winter lettuce, spinach, salad onions, and overwintering varieties of broad beans and peas. Harvest sweetcorn, tomatoes, beans, courgettes, soft fruit, and main-crop potatoes.
Source and methodology
Frost-date averages from NOAA Climate Data Online within USDA zone 4. Hardiness boundaries from the USDA Plant Hardiness Zone Map (2023). Crop timing curated against US Cooperative Extension Service publications (UNL, UMN, NC State, Texas A&M, UF/IFAS, Oregon State) and cross-referenced against the RHS sowing calendar. Curated by the Growli editorial team.
Keep going
- ← July in zone 4
- September in zone 4 →
- All zones — what to plant in August
- USDA Zone 4 — frost dates and crop list
- Full 12-month planting calendar