Zone 4b planting calendar
In zone 4b the last spring frost usually comes around May 8 and the first fall frost around October 1: about 145 frost-free days. Here is what to do each month.
Typical frost dates
- Last spring frost
- May 8 Middle half of the zone: May 5 – May 17. Over by May 22 in 9 of 10 years.
- First fall frost
- October 1 Middle half of the zone: Sep 27 – Oct 4. After Sep 18 in 9 of 10 years.
- Frost-free season
- about 145 days
- Coldest winter nights
- -25 to -20 °F
- ZIP codes in the zone
- 1,256
Most of its weather stations are in Montana, South Dakota, Minnesota, Wisconsin, Wyoming and Maine and 8 more.
Places in zone 4b
Zones measure winter cold, so frost dates still vary from place to place. A few weather stations across the zone:
| Place | State | Last spring frost | First fall frost | Frost-free days |
|---|---|---|---|---|
| Brookings | South Dakota | May 6 | Oct 1 | 145 |
| Frenchville Aroostook | Maine | May 6 | Oct 2 | 147 |
| Edgeley | North Dakota | May 7 | Oct 2 | 148 |
| Shoshoni | Wyoming | May 7 | Oct 3 | 145 |
| Rice Lake | Wisconsin | May 8 | Oct 2 | 145 |
| Forsyth | Montana | May 9 | Sep 29 | 142 |
| Two Harbors | Minnesota | May 12 | Oct 6 | 145 |
| Covington | Michigan | May 17 | Sep 30 | 134 |
Month by month in zone 4b
Every job for all 60 crops, in the month it starts.
January
A quiet month: order seeds and sketch the beds.
February
March
Start indoors
- Tomatoes Mar 13–27
- Tomatillos Mar 13–27
- Cabbage Mar 13–27
- Broccoli Mar 13–27
- Cauliflower Mar 13–27
- Chives Mar 13–27
- Basil Mar 27 – Apr 10
- Marigolds Mar 27 – Apr 10
April
Sow outside
- Arugula Apr 3 – May 1
- Radishes Apr 3 – May 15
- Shallots (shallot sets) Apr 10–24
- Collard greens Apr 10 – May 1
- Kohlrabi Apr 10 – May 1
- Turnips Apr 10 – May 1
- Asparagus (asparagus crowns) Apr 10 – May 1
- Rhubarb (rhubarb crowns) Apr 10 – May 1
- Mustard greens Apr 10 – May 8
- Potatoes (seed potatoes) Apr 10 – May 8
- Lettuce Apr 10 – May 22
- Green onions Apr 10 – May 22
- Bok choy Apr 17 – May 8
- Parsnips Apr 17 – May 15
- Carrots Apr 17 – May 22
- Beets Apr 17 – May 22
- Cilantro Apr 24 – May 22
- Swiss chard Apr 24 – May 29
Plant out
- Cabbage Apr 10–24
- Onions Apr 10–24
- Strawberries (strawberry plants) Apr 10 – May 1
- Broccoli Apr 17 – May 8
- Leeks Apr 17 – May 15
- Chives Apr 17 – May 15
- Cauliflower Apr 24 – May 8
- Parsley Apr 24 – May 22
- Thyme Apr 24 – May 22
- Mint Apr 24 – May 22
May
Sow outside
- Dill May 1–29
- Sunflowers May 8 – Jun 5
- Zucchini May 15–29
- Zinnias May 15–29
- Nasturtiums May 15–29
- Cosmos May 15–29
- Cucumbers May 15 – Jun 5
- Winter squash May 15 – Jun 5
- Pumpkins May 15 – Jun 5
- Green beans May 15 – Jun 5
- Sweet corn May 15 – Jun 5
- Watermelons May 22 – Jun 5
- Cantaloupes May 22 – Jun 5
- Okra May 22 – Jun 12
Plant out
- Oregano May 1–22
- Sage May 1–22
- Rosemary May 8–29
- Lavender May 8–29
- Tomatoes May 15–29
- Tomatillos May 15–29
- Celery May 15–29
- Marigolds May 15–29
- Peppers May 22 – Jun 5
- Hot peppers May 22 – Jun 5
- Eggplant May 22 – Jun 5
- Basil May 22 – Jun 5
- Sweet potatoes (sweet potato slips) May 29 – Jun 19
Sow for fall
- Brussels sprouts May 7–28
June
Sow for fall
- Cabbage Jun 4 – Jul 2
- Cauliflower Jun 11 – Jul 2
- Broccoli Jun 11 – Jul 9
Start picking
- Collard greens Jun 4 – Nov 12
- Strawberries Jun 5 – Jul 3
- Beets Jun 6 – Jul 21
- Cilantro Jun 8 – Jul 31
- Parsley Jun 8 – Nov 12
- Thyme Jun 8 – Nov 12
- Cabbage Jun 9 – Jul 23
- Green onions Jun 9 – Aug 5
- Dill Jun 10 – Aug 5
- Broccoli Jun 11 – Jul 27
- Swiss chard Jun 13 – Oct 15
- Marigolds (in bloom) Jun 14 – Oct 1
- Oregano Jun 15 – Nov 2
- Carrots Jun 16 – Aug 10
- Cauliflower Jun 18 – Jul 27
- Basil Jun 21 – Oct 1
- Potatoes Jun 24 – Sep 5
- Zucchini Jun 29 – Oct 1
- Nasturtiums (in bloom) Jun 29 – Oct 1
- Sage Jun 30 – Nov 12
July
Sow for fall
- Cucumbers Jul 2–16
- Green beans Jul 2–16
- Zucchini Jul 9–23
- Peas Jul 9–23
- Carrots Jul 9–30
- Beets Jul 9–30
- Kale Jul 9 – Aug 6
- Collard greens Jul 9 – Aug 6
- Green onions Jul 16–30
- Cilantro Jul 23 – Aug 6
- Lettuce Jul 23 – Aug 13
- Kohlrabi Jul 23 – Aug 13
- Bok choy Jul 23 – Aug 13
- Spinach Jul 23 – Aug 20
- Turnips Jul 23 – Aug 20
- Arugula Jul 30 – Aug 27
- Mustard greens Jul 30 – Aug 27
Start picking
- Cucumbers Jul 4 – Oct 1
- Green beans Jul 4 – Oct 1
- Lavender Jul 7 – Sep 1
- Rosemary Jul 7 – Oct 15
- Shallots Jul 9 – Aug 12
- Onions Jul 9 – Aug 22
- Garlic Jul 10–31
- Okra Jul 11 – Oct 1
- Tomatoes Jul 14 – Oct 1
- Zinnias (in bloom) Jul 14 – Oct 1
- Cosmos (in bloom) Jul 14 – Oct 1
- Leeks Jul 16 – Nov 12
- Sunflowers (in bloom) Jul 17 – Sep 13
- Sweet corn Jul 19 – Sep 3
- Tomatillos Jul 19 – Sep 27
- Peppers Jul 21 – Oct 1
- Eggplant Jul 26 – Oct 1
- Cantaloupes Jul 31 – Sep 4
- Watermelons Jul 31 – Sep 13
- Hot peppers Jul 31 – Oct 1
August
Sow for fall
- Radishes Aug 13 – Sep 3
Start picking
- Winter squash Aug 3 – Oct 1
- Celery Aug 8 – Oct 3
- Pumpkins Aug 13 – Oct 1
- Sweet potatoes Aug 27 – Oct 1
- Beets Aug 28 – Oct 2
- Arugula Aug 29 – Oct 6
- Mustard greens Aug 29 – Oct 11
- Cabbage Aug 31 – Oct 28
September
Sow for fall
- Garlic (garlic cloves) Sep 17 – Oct 22
Start picking
- Bok choy Sep 1 – Oct 7
- Spinach Sep 1 – Oct 9
- Lettuce Sep 1 – Oct 13
- Turnips Sep 1 – Oct 19
- Peas Sep 2 – Oct 1
- Cauliflower Sep 2 – Oct 15
- Broccoli Sep 2 – Oct 25
- Brussels sprouts Sep 4 – Nov 12
- Kohlrabi Sep 6 – Oct 12
- Cilantro Sep 6 – Oct 15
- Radishes Sep 7 – Oct 3
- Carrots Sep 7 – Oct 19
- Green onions Sep 14 – Oct 26
- Parsnips Sep 17 – Nov 12
October
Nothing new to start; keep picking what is still growing, then clear finished beds and spread compost.
November
Nothing to sow; clean and store the tools and note what grew well.
December
A month to rest the soil and plan next year.