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Zone 3B — September

What to Plant in September in Zone 3B

September in Zone 3B: 0 crops to start indoors, 0 to plant or direct sow outside, and 94 entering harvest window. Last frost averages May 18. Reference city: International Falls, MN.
Updated August 12, 2026 · Frost data from NOAA 1991-2020 Climate Normals
0 Start Indoors
0 Plant Outside
94 Harvest
Frost risk: Cleared

Frost season has cleared in Zone 3B. The last spring frost typically passed by May 18, and the very latest 10% chance closed by June 1. Tender crops are safe to plant out.

See full Zone 3B frost outlook →

Start Indoors in September

Nothing to start seeds indoors in September for Zone 3B.
Next window: November — 1 variety, including Garlic.

Plant Outside in September

Nothing to plant or sow outside in September for Zone 3B.
Next window: November — 1 variety, including Garlic.

Harvest in September

Plant Type Planted / Sown Harvest Window
Baby Blue Hubbard Winter Squash squash May 25 Sep 2
Cinderella Pumpkin squash May 25 Sep 12
Golden Hubbard Winter Squash squash May 25 Sep 2
Green Hubbard Winter Squash squash May 25 Sep 12
Green Striped Cushaw Crookneck Winter Squash squash May 25 Sep 2
Indian Spring Mix Hollyhock Flowers flower May 18 Sep 15 – Sep 16 (before frost)
Jack Be Little Pumpkin squash May 25 Sep 2
Long Island Cheese Winter Squash squash May 25 Sep 2
Paris Yellow Pumpkin squash May 25 Sep 2
Pink Banana Jumbo Winter Squash squash May 25 Sep 2 – Sep 12
Summer Carnival Mix Hollyhock Flowers flower May 18 Sep 15 – Sep 16 (before frost)
White Cushaw Crookneck Winter Squash squash May 25 Sep 2
All Season Cabbage (fall planting) brassica Jun 30 Sep 18
All Year Round (fall planting) lettuce Jun 30 Sep 11
All Year Round Cauliflower (fall planting) brassica Jun 30 Sep 3
Angelica (fall planting) herb Jun 30 Sep 28
Baby Blue Eyes Flowers (fall planting) flower Jun 30 Sep 28
Bachelor's button edible flowers (fall planting) flower Jun 30 Sep 18
Birds Eye Hot Peppers pepper Jun 1 Sep 9 – Sep 19
Bloody Butcher Corn vegetable Jun 1 Sep 9 – Sep 19
Bouquet Dill (fall planting) herb Jun 30 Sep 3
Broad Windsor Fava Bean (fall planting) legume Jun 30 Sep 23
Broccolini (fall planting) brassica Jun 30 Sep 8
Brunswick Cabbage (fall planting) brassica Jun 30 Sep 28
Butterhead Lettuce (fall planting) lettuce Jun 30 Sep 3
Calabrese Broccoli (fall planting) brassica Jun 30 Sep 3
California Bluebell (fall planting) flower Jun 30 Sep 3
Cascadia Sugar Snap Pea (fall planting) legume Jun 30 Sep 5
Charleston Wakefield Cabbage (fall planting) brassica Jun 30 Sep 13
Chinese Forget-Me-Not Flowers (fall planting) flower Jun 30 Sep 23
Chioggia Beet (fall planting) root vegetable Jun 30 Sep 3
Copenhagen Cabbage (fall planting) brassica Jun 30 Sep 3
Cosmic Purple Carrot (fall planting) root vegetable Jun 30 Sep 13
Crimson Clover (fall planting) cover crop Jun 30 Sep 28
Crisphead (fall planting) lettuce Jun 30 Sep 13
Curly Kale (fall planting) lettuce Jun 30 Sep 3
Danvers Carrot (fall planting) root vegetable Jun 30 Sep 18
Dark Green Romaine (fall planting) lettuce Jun 30 Sep 8
Delica kabocha squash squash Jun 1 Sep 4 – Sep 19
Di Cicco Broccoli (fall planting) brassica Jun 30 Sep 3
Early Jersey Wakefield Cabbage (fall planting) brassica Jun 30 Sep 13
Early Purple Broccoli (fall planting) brassica Jun 30 Sep 3
Endive / Escarole (fall planting) lettuce Jun 30 Sep 3
Evergreen Parsley (fall planting) herb Jun 30 Sep 23
Full Heart Batavian (fall planting) lettuce Jun 30 Sep 28
Georgia Southern Collard Greens (fall planting) lettuce Jun 30 Sep 18
German Chamomile (fall planting) herb Jun 30 Sep 3
Globe Gilia Flowers (fall planting) flower Jun 30 Sep 18
Glory of Enkhuizen Cabbage (fall planting) brassica Jun 30 Sep 28
Golden Acre Cabbage (fall planting) brassica Jun 30 Sep 3
Golden Beet (fall planting) root vegetable Jun 30 Sep 3
Green Arrow Pea (fall planting) legume Jun 30 Sep 8
Hairy vetch cover crop stands (fall planting) cover crop Jun 30 Sep 28
Iceberg (fall planting) lettuce Jun 30 Sep 13
Igloo Cauliflower (fall planting) brassica Jun 30 Sep 8
Lacinato Kale (fall planting) lettuce Jun 30 Sep 3
Lacy Phacelia Flowers (fall planting) flower Jun 30 Sep 13
Little Marvel Pea (fall planting) legume Jun 30 Sep 1
Love-in-a-Mist Flowers (fall planting) flower Jun 30 Sep 23
Mammoth Dill (fall planting) herb Jun 30 Sep 3
Mammoth Melting Sugar Snow Pea (fall planting) legume Jun 30 Sep 12
Medium Red Clover Cover Crop (fall planting) cover crop Jun 30 Sep 13
Michihili Cabbage (fall planting) brassica Jun 30 Sep 8
Morris Heading (fall planting) lettuce Jun 30 Sep 18
Mâche (Corn Salad) (fall planting) lettuce Jun 30 Sep 22
Napa Cabbage (fall planting) brassica Jun 30 Sep 28
Nodding Catchfly Flowers (fall planting) flower Jun 30 Sep 28
Oregon Giant Snow Pea (fall planting) legume Jun 30 Sep 12
Oregon Sugar Pod Snow Pea (fall planting) legume Jun 30 Sep 6
Orion Florence Fennel (fall planting) vegetable Jun 30 Sep 28
Radicchio (fall planting) lettuce Jun 30 Sep 23
Rapeseed Cover Crop (fall planting) cover crop Jun 30 Sep 8
Rapini Broccoli Raab (fall planting) brassica Jun 30 Sep 3
Red Acre Cabbage (fall planting) brassica Jun 30 Sep 18
Red Romaine (fall planting) lettuce Jun 30 Sep 8
Romaine Lettuce (fall planting) lettuce Jun 30 Sep 13
Scarlet Flax Flowers (fall planting) flower Jun 30 Sep 8
Shelling Pea (fall planting) legume Jun 30 Sep 8
Snow Pea (fall planting) legume Jun 30 Sep 8
Snowball Self-Blanche Cauliflower (fall planting) brassica Jun 30 Sep 3
Sweet Marjoram (fall planting) herb Jun 30 Sep 28
Tom Thumb (fall planting) lettuce Jun 30 Sep 8
Tuscany Black (fall planting) lettuce Jun 30 Sep 13
Vates Collard (fall planting) lettuce Jun 30 Sep 13
Verona Red (fall planting) lettuce Jun 30 Sep 30
Vienna Purple Kohlrabi (fall planting) brassica Jun 30 Sep 3
Vienna White Kohlrabi (fall planting) brassica Jun 30 Sep 3
Viola and pansy edible flowers (fall planting) flower Jun 30 Sep 8
Violetta Purple Cauliflower (fall planting) brassica Jun 30 Sep 3
Waltham 29 Broccoli (fall planting) brassica Jun 30 Sep 28
Wando Pea (fall planting) legume Jun 30 Sep 6
Watermelon Radishes (fall planting) root vegetable Jun 30 Sep 3
Nantes Carrot (fall planting) root vegetable Jul 1 Sep 14
Sugar Snap Pea (fall planting) legume Jul 15 Sep 23

Key Tasks for September in Zone 3B

  1. 1 Check soil moisture before watering — stick a finger 2 inches into the soil. Water only when the soil is dry at that depth. Consistent moisture is more important than frequency.
Back to full Zone 3B planting calendar
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