September in Zone 4
September in Zone 4 (last frost early – mid may, first frost mid september – mid october). There are 4 crops to sow, transplant, or harvest this month.
Jump to another month
- Min Winter Temp
- -30 to -20 °F / -34 to -29 °C
- Last Spring Frost
- Early – mid May
- First Fall Frost
- Mid September – mid October
- Growing Season
- 120–150 days
- Annual Rainfall
- 20–45 in
September overview
September is the start of fall and a second growing season for cool-zone gardeners. Temperatures cool to optimal ranges for leafy greens and root vegetables. First frost arrives in cold zones, triggering final harvests.
Direct sowing fall crops; first frost possible in Zones 3–5; harvesting winter squash and pumpkins; planting garlic and spring bulbs; fall clean-up begins.
- Season
- fall
- Temperature trend
- Rapidly cooling in northern zones; first frosts possible in cold areas after mid-month.
- Daylight
- Fall equinox around September 22; days and nights equal, then nights lengthen.
- Zone 4 last frost
- Early – mid May
- Zone 4 first frost
- Mid September – mid October
0
Sow indoors
3
Sow outdoors
0
Transplant
1
Harvest
1
Maintenance
🌿 Sow outdoors
Sow these directly outdoors
Soil and weather are right to sow these straight into the garden where they will grow.
Spinach
Fall/overwinter crop: sow late summer; survives hard frost under cover.
Radishes
Fall sowing gives crisper, milder roots than spring.
Garlic
Plant cloves 2 in deep, pointy end up, 6 in apart in fall; mulch heavily. Harvest the following midsummer.
🧺 Harvest
Harvest these now
These crops are coming ripe — pick regularly to keep plants productive.
Onions
Harvest when tops flop and brown; cure 2 weeks before storing.
🛠️ Maintenance
Keep the garden growing
Mid-season upkeep keeps plants healthy and productive.
📌 Water deeply and less often, mulch to hold moisture, side-dress heavy feeders, scout for pests, and succession-sow quick crops.
General September tasks
These apply broadly regardless of zone — a useful checklist alongside the zone-specific tasks above.
- ✓Plant garlic cloves 4–6 weeks before ground freezes
- ✓Direct sow spinach, mâche, and overwintering lettuce varieties
- ✓Harvest winter squash, pumpkins, and dried beans as plants die back
- ✓Plant spring bulbs: tulips, daffodils, hyacinths, crocuses
- ✓Divide and transplant perennials: hostas, daylilies, irises
- ✓Take cuttings of tender perennials to overwinter indoors
- ✓Apply fall fertilizer to lawns and perennial beds
- ✓Begin fall clean-up: remove spent annuals, cut back perennials
⚠ Watch-outs for September
- ⚠First frost warnings in cold zones — protect tender crops or harvest before freeze
- ⚠Don't cut back ornamental grasses or late-season perennials yet — they provide fall habitat
- ⚠Fall is prime time for lawn grubs — apply biological controls (milky spore, nematodes) now
- ⚠Deer browse pressure increases as natural food sources diminish
September in Zone 4: common questions
What can I plant in September in Zone 4?＋
In September, Zone 4 gardeners can sow or transplant Spinach, Radishes, and Garlic. September in Zone 4 (last frost early – mid may, first frost mid september – mid october). There are 4 crops to sow, transplant, or harvest this month.
When is the last and first frost in Zone 4?＋
Zone 4 typically has its last spring frost around Early – mid May and its first fall frost around Mid September – mid October, giving a growing season of roughly 120–150 days. Always check a local frost-date source, since microclimates vary.
What's ready to harvest in September in Zone 4?＋
In September, Zone 4 gardeners are typically harvesting Onions. Pick regularly — frequent harvesting keeps most crops producing longer.