Now
24°C · Clear
Today
27° / 18°
Soil 6 cm
22°C
First frost
~32 days (Oct 10)
Gardening in Grand Forks
AI field guide · refreshed weeklyGrand Forks Gardening: Early September – Harvest, Extend, and Plan for Frost
You're in zone 4a with 32 days until the average first frost (October 10). Soil at 22°C (72°F) is still warm enough for cool-season crops to germinate and establish before soil temps drop below 10°C in late September. Your 153 frost-free days mean every week counts now—prioritize what you want to harvest versus what you're willing to lose to an early freeze.
Sow outdoors now
Spinach (Spinacia oleracea)
Sow 'Space' or 'Bloomsdale Long Standing' directly outdoors now; germinates in 7–10 days at 22°C soil and will mature before frost in 40–50 days.
Arugula (Eruca vesicana)
Direct seed 'Roquette' or 'Astro'; thrives in cool soil and ready to harvest in 30–40 days, even after light frosts.
Radish (Raphanus sativus)
Sow 'Cherry Belle' or 'French Breakfast' for a quick 25–30 day crop before hard freeze; tolerates frost well.
Mâche (Valerianella locusta)
Direct seed now for a hardy, slow-growing winter green; survives hard frosts and can be harvested into November under row cover.
Turnip (Brassica rapa)
Sow 'Purple Top' or 'Tokyo Cross' for roots and greens; matures in 50–60 days and improves in flavor after light frost.
Start indoors now
Kale (Brassica oleracea var. acephala)
Start 'Lacinato' or 'Winterbor' indoors now for transplant in 2–3 weeks; these cold-hardy varieties sweeten after frost and produce through November.
Cabbage (Brassica oleracea var. capitata)
Seed 'January King' or 'Tundra' indoors for transplant by late September; both are cold-tolerant and store well.
Chard (Beta vulgaris subsp. cicla)
Start 'Bright Lights' or 'Fordhook Giant' indoors for transplant in 2–3 weeks; will produce tender leaves through October.
Harvest now
Tomato (Solanum lycopersicum)
Pick all fruit now—mature green, turning, or ripe—before the first frost hits in 32 days; green tomatoes ripen indoors in 2–3 weeks at room temperature.
Pepper (Capsicum annuum)
Harvest all peppers (green or colored) before frost; they won't ripen further outdoors once nights drop below 15°C.
Cucumber (Cucumis sativus)
Pick all remaining fruit; vines will die at first frost and any green fruit will not mature.
Zucchini & Summer Squash (Cucurbita pepo)
Harvest regularly now; plants are frost-tender and will collapse within days of a freeze.
Tasks this week
- Pull spent tomato, pepper, and squash plants by mid-week to reduce disease pressure and clear space for fall crops.
- Install row cover or cold frames over newly seeded spinach, arugula, and radish to protect against the 32 km/h (20 mph) winds forecast and any surprise frost.
- Water newly sown seeds deeply after planting; the next rain isn't forecast until September 14, and 22°C soil will dry quickly.
- Deadhead spent flowers on perennials (coneflower, black-eyed Susan) to redirect energy into root hardening before winter.
- Scout for Japanese beetles and grasshoppers on remaining brassicas; hand-pick or use neem oil if populations are high.
Watch out for
- Early frost risk: An unexpected freeze could arrive any time after September 10; keep frost cloth and cloches ready for tender transplants.
- High wind (up to 37 km/h on Sept 11): Stake or support tall fall crops and newly transplanted seedlings to prevent root damage.
- Dry conditions: No rain forecast until September 14; water newly seeded beds and transplants daily if soil surface dries.
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