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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: February — 2 varieties, including King Richard Leek, Viola and pansy edible flowers.

Plant Outside in September

Nothing to plant or sow outside in September for Zone 3B.
Next window: October — 11 varieties, including Asian Tempest Garlic, Chengdu Garlic, Chesnok Red Garlic.

Harvest in September

Plant Type Planted / Sown Harvest Window
Cinderella Pumpkin squash May 25 Sep 17
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 7
Indian Spring Mix Hollyhock Flowers flower May 18 Sep 15 – Sep 16 (before frost)
Long Island Cheese Winter Squash squash May 25 Sep 10
Mammoth Sandwich Island Salsify root vegetable May 25 Sep 22
Paris Yellow Pumpkin squash May 25 Sep 2
Pink Banana Jumbo Winter Squash squash May 25 Sep 2 – Sep 12
Southport Red Globe Onions allium May 18 Sep 15
Southport White Globe Onions allium May 18 Sep 15
Spanish Sweet White Onions allium May 18 Sep 5 – Sep 15
Summer Carnival Mix Hollyhock Flowers flower May 18 Sep 15 – Sep 16 (before frost)
White Cushaw Crookneck Winter Squash squash May 25 Sep 2
Adirondack Blue Potato (fall planting) root vegetable Jun 30 Sep 25
All Season Cabbage (fall planting) brassica Jun 30 Sep 18
All Year Round Cauliflower (fall planting) brassica Jun 30 Sep 3
All Year Round Lettuce (fall planting) lettuce Jun 30 Sep 11
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 18
Broadleaf Full Heart Batavian Endive (fall planting) lettuce Jun 30 Sep 28
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
Carolina Cross Watermelon melon Jun 1 Sep 9
Charleston Wakefield Cabbage (fall planting) brassica Jun 30 Sep 8
Chinese Forget-Me-Not Flowers (fall planting) flower Jun 30 Sep 23
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 Lettuce (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 Lettuce (fall planting) lettuce Jun 30 Sep 8
Delica Kabocha Squash squash Jun 1 Sep 4 – Sep 19
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
Georgia Southern Collard Greens (fall planting) lettuce Jun 30 Sep 23
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 Lettuce (fall planting) lettuce Jun 30 Sep 13
Igloo Cauliflower (fall planting) brassica Jun 30 Sep 8
King Richard Leek (fall planting) allium Jun 30 Sep 13
Lacinato Kale (fall planting) lettuce Jun 30 Sep 3
Little Marvel Pea (fall planting) legume Jun 30 Sep 1
Love-in-a-Mist Flowers (fall planting) flower Jun 30 Sep 8
Mammoth Dill (fall planting) herb Jun 30 Sep 3
Mammoth Melting Sugar Snow Pea (fall planting) legume Jun 30 Sep 13
Medium Red Clover Cover Crop (fall planting) cover crop Jun 30 Sep 13
Michihili Cabbage (fall planting) brassica Jun 30 Sep 8
Morris Heading Collard (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 8
Nodding Catchfly Flowers (fall planting) flower Jun 30 Sep 28
Oregon Sugar Pod Snow Pea (fall planting) legume Jun 30 Sep 6
Orion Florence Fennel (fall planting) vegetable Jun 30 Sep 28
Par-Cel Cutting Celery (fall planting) vegetable Jun 30 Sep 23
Queen Anne's Lace Flowers (fall planting) flower Jun 30 Sep 13
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 Lettuce (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
Tom Thumb Lettuce (fall planting) lettuce Jun 30 Sep 8
Tuscany Black Kale (fall planting) lettuce Jun 30 Sep 13
Vates Collard (fall planting) lettuce Jun 30 Sep 13
Verona Red Chicory (fall planting) lettuce Jun 30 Sep 30
Vienna Purple 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
Yukon Gold Potato (fall planting) root vegetable Jun 30 Sep 28
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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