Now
23°C · Overcast
Today
24° / 18°
Soil 6 cm
20°C
First frost
~44 days (Oct 22)
Gardening in Duluth
AI field guide · refreshed weeklyDuluth Garden Guide: September 8–14, 2026
You're in zone 5a with 44 days until your average first frost (October 22). Soil at 20°C (68°F) is still warm enough for root development, but cooling fast. This is your final window for fall crops that need 6–8 weeks to mature before hard freeze. Spring frost typically arrives May 5, giving you a 170-day growing season.
Sow outdoors now
Spinach (Bloomsdale, Space or Tyee)
Sow directly now; germinates well in 18–20°C soil and matures in 40–50 days before frost. Plant 2 cm deep, 10 cm apart in rows.
Arugula (Roquette)
Fast crop (30–40 days), tolerates cool nights, and actually improves in flavor after light frost. Sow 1 cm deep, thin to 15 cm spacing.
Mâche (Corn Salad)
Cold-hardy green that germinates in cool soil and overwinters under mulch for early spring harvest. Sow 1 cm deep, broadcast or in rows.
Radish (Cherry Belle, French Breakfast)
Matures in 25–30 days; sow 1 cm deep, 5 cm apart. Successive sowings through mid-September work if soil stays above 15°C.
Turnip (Purple Top White Globe)
Roots and greens both edible; 60–70 days to maturity. Sow 1 cm deep, thin to 15 cm. Flavor sweetens after frost.
Start indoors now
Onions (Walla Walla, Copra storage types)
Start seeds indoors now for transplant in spring; they need 120+ days to bulb. Keep at 15–18°C under lights.
Leeks (Titan, King Richard)
Sow indoors for spring transplant; 120–150 days to harvest. Thin seedlings to 5 cm spacing under lights.
Harvest now
Tomatoes (all types)
Pick all fruit before first frost (Oct 22). Mature green tomatoes ripen indoors at 18–21°C in 2–3 weeks; store in paper bag with banana to speed ethylene.
Peppers (sweet and hot)
Harvest now; frost kills plants. Green peppers ripen to red/yellow indoors slowly; better to pick mature color before frost.
Beans (bush and pole)
Pick pods before pods yellow or beans harden. Frost will kill plants within 2–3 weeks; prioritize harvest.
Squash and Pumpkins
Cut with 5 cm stem, cure in warm (18–21°C), dry spot for 10 days before storage. Frost-damaged fruit rots quickly.
Tasks this week
- Cut back or remove spent tomato, pepper, and bean plants after final harvest to reduce disease and clear space for fall crops.
- Mulch spinach, arugula, and mâche with 5 cm straw after germination to insulate soil and extend season.
- Clean and oil garden tools before storage; drain hoses and irrigation lines before freeze.
- Scout for late-season pests (aphids, cabbage moths on brassicas); handpick or use neem oil if needed.
- Collect seeds from open-pollinated varieties (beans, peas, squash) before frost; dry in paper bags indoors.
Watch out for
- Heavy rain (28 mm today, 23 mm on Sept 11) can rot ripening fruit and split squash; harvest before storms and ensure good drainage.
- Frost risk jumps sharply after Oct 1; tender crops (tomatoes, peppers, basil, squash) must be harvested or protected by then.
- Powdery mildew thrives in cool, humid conditions (88% humidity today); thin plants for air flow and remove infected leaves.
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