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Seasonal Planting Calendar

Updated May 2026 · 0 plants · 0 actions

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Northern Tier has a 108-day growing season — short, sharp, and rewarding for gardeners who plan around frost. September is the editorial lens for what to sow indoors and direct-seed now. Pick a USDA zone above to compare calendars.

Zone 3b in September

☀️ In-season0 weeks to first frost
September is prime growing season for Northern Tier — your 108-day window means every warm week counts. Transplant tomatoes and peppers once nights are reliably above 50°F, succession-sow lettuces every 2 weeks, and plan for first frost 0 weeks from now.

About Zone 3b

USDA Zone 3b (Northern Tier) has an average last frost of May 30 and first frost of Sep 15, giving roughly 108 frost-free days. Around 110 frost-free days. Lean on season extenders and indoor seed starting. Sources: UMaine Extension, UMN Extension & Northern Plains gardeners.

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