Now
25°C · Clear
Today
26° / 16°
Soil 6 cm
20°C
First frost
~37 days (Oct 15)
Gardening in International Falls
AI field guide · refreshed weeklyGardening in International Falls: Early September — Race the Frost
You're in zone 4a with 37 days until the average first frost (October 15). Soil at 20°C is still warm enough for germination, but nights are already dipping into the teens. This is your last realistic window for cool-season crops and frost-tender annuals; anything planted now must mature before mid-October. Spring frost typically arrives May 14, giving you a 154-day growing season.
Sow outdoors now
Spinach (Bloomsdale, Space or Tyee)
Direct sow now for a 40–50 day harvest before hard frost. Germinates well at 20°C soil; thin to 10 cm (4 in) apart. Tolerates light frosts once established.
Arugula (Roquette)
Sow thickly in rows 15 cm (6 in) apart; ready to cut in 30–40 days. Flavor improves after light frost. Prefers cool soil, so this timing is ideal.
Radish (Cherry Belle, Icicle)
Matures in 25–30 days at current soil temps. Sow every 10 days for succession harvests through October.
Mâche (Corn Salad)
Extremely cold-hardy; sow now for fall and early winter harvests. Germinates slowly (2–3 weeks) but thrives as temps drop.
Turnip (Purple Top, Tokyo Cross)
Sow for 50–60 day maturity; roots sweeten after frost. Thin to 15 cm (6 in) spacing; greens are also edible.
Start indoors now
Kale (Lacinato, Winterbor)
Start indoors now for transplant in 3–4 weeks; these will mature outdoors by November and survive hard frosts. Zone 4a gardeners often overwinter kale under row cover.
Cabbage (Savoy, Red Acre)
Sow indoors for October transplant; 60–80 day varieties will head before heavy snow. Seedlings need 12–14 hours light and cool nights (15–18°C).
Harvest now
Tomatoes (all varieties)
Pick all fruit, including green ones; ripen indoors at room temperature or in a paper bag with a ripe banana. Frost will kill vines within 37 days.
Peppers (sweet and hot)
Harvest all mature peppers before frost; immature fruit will not ripen after picking. Green peppers are edible; store in cool place for slow ripening.
Beans (bush and pole)
Pick all pods; frost will blacken plants. Dry mature pods for seed saving or shell fresh for storage.
Squash and Pumpkins
Harvest fully mature fruit with hard skin and dry stem. Cure in a warm, dry place (18–21°C) for 7–10 days before storage.
Tasks this week
- Clean up spent pea and bean plants to reduce disease pressure; compost only if disease-free.
- Deadhead perennials (coneflower, black-eyed Susan) if you want to prevent self-seeding, or leave for seed and wildlife.
- Mulch garlic beds (if planted) and perennial beds with 5–7 cm (2–3 in) of compost or aged manure before hard frost.
- Drain and store garden hoses; shut off outdoor water before the first hard freeze.
- Collect seeds from herbs (dill, cilantro, parsley) and flowers before rain or wind scatters them.
Watch out for
- Early frost risk: The forecast shows 5°C lows by September 13; tender annuals (basil, tender herbs) will die. Pull or protect now.
- Heavy rain September 14 (36 mm / 1.4 in) may cause root rot in wet soil; ensure drainage is clear around beds.
- Powdery mildew thrives in cool, humid conditions (current humidity 83%); thin crowded plants and water at soil level only.
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