Zone 4a planting calendar
In zone 4a the last spring frost usually comes around May 12 and the first fall frost around September 28: about 137 frost-free days. Here is what to do each month.
Typical frost dates
- Last spring frost
- May 12 Middle half of the zone: May 9 – May 18. Over by May 27 in 9 of 10 years.
- First fall frost
- September 28 Middle half of the zone: Sep 24 – Oct 1. After Sep 15 in 9 of 10 years.
- Frost-free season
- about 137 days
- Coldest winter nights
- -30 to -25 °F
- ZIP codes in the zone
- 783
Most of its weather stations are in North Dakota, Montana, Minnesota, Wisconsin, South Dakota and New York and 6 more.
Places in zone 4a
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 |
|---|---|---|---|---|
| Caribou | Maine | May 7 | Oct 1 | 143 |
| Ada | Minnesota | May 11 | Sep 27 | 137 |
| Mellette | South Dakota | May 11 | Sep 27 | 137 |
| Sidney | Montana | May 11 | Sep 27 | 137 |
| Carrington | North Dakota | May 12 | Sep 27 | 137 |
| Stillwater Reservoir | New York | May 15 | Oct 2 | 139 |
| Clam Lake | Wisconsin | May 16 | Sep 30 | 136 |
| Sybille Research Unit | Wyoming | May 22 | Sep 24 | 125 |
Month by month in zone 4a
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
- Peppers Mar 3–17
- Hot peppers Mar 3–17
- Eggplant Mar 3–17
- Onions Mar 3–17
- Parsley Mar 3–17
- Tomatoes Mar 17–31
- Tomatillos Mar 17–31
- Cabbage Mar 17–31
- Broccoli Mar 17–31
- Cauliflower Mar 17–31
- Chives Mar 17–31
- Basil Mar 31 – Apr 14
- Marigolds Mar 31 – Apr 14
April
Sow outside
- Arugula Apr 7 – May 5
- Radishes Apr 7 – May 19
- Shallots (shallot sets) Apr 14–28
- Collard greens Apr 14 – May 5
- Kohlrabi Apr 14 – May 5
- Turnips Apr 14 – May 5
- Asparagus (asparagus crowns) Apr 14 – May 5
- Rhubarb (rhubarb crowns) Apr 14 – May 5
- Mustard greens Apr 14 – May 12
- Potatoes (seed potatoes) Apr 14 – May 12
- Lettuce Apr 14 – May 26
- Green onions Apr 14 – May 26
- Bok choy Apr 21 – May 12
- Parsnips Apr 21 – May 19
- Carrots Apr 21 – May 26
- Beets Apr 21 – May 26
- Cilantro Apr 28 – May 26
- Swiss chard Apr 28 – Jun 2
Plant out
- Cabbage Apr 14–28
- Onions Apr 14–28
- Strawberries (strawberry plants) Apr 14 – May 5
- Broccoli Apr 21 – May 12
- Leeks Apr 21 – May 19
- Chives Apr 21 – May 19
- Cauliflower Apr 28 – May 12
- Parsley Apr 28 – May 26
- Thyme Apr 28 – May 26
- Mint Apr 28 – May 26
Start picking
- Asparagus Apr 28 – Jun 23
May
Sow outside
- Dill May 5 – Jun 2
- Sunflowers May 12 – Jun 9
- Zucchini May 19 – Jun 2
- Zinnias May 19 – Jun 2
- Nasturtiums May 19 – Jun 2
- Cosmos May 19 – Jun 2
- Cucumbers May 19 – Jun 9
- Winter squash May 19 – Jun 9
- Pumpkins May 19 – Jun 9
- Green beans May 19 – Jun 9
- Sweet corn May 19 – Jun 9
- Watermelons May 26 – Jun 9
- Cantaloupes May 26 – Jun 9
- Okra May 26 – Jun 16
Plant out
Sow for fall
- Brussels sprouts May 4–25
Start picking
June
Plant out
- Sweet potatoes (sweet potato slips) Jun 2–23
Sow for fall
- Cabbage Jun 1–29
- Cauliflower Jun 8–29
- Broccoli Jun 8 – Jul 6
- Cucumbers Jun 29 – Jul 13
- Green beans Jun 29 – Jul 13
Start picking
- Collard greens Jun 8 – Nov 9
- Strawberries Jun 9 – Jul 7
- Beets Jun 10 – Jul 25
- Cilantro Jun 12 – Aug 4
- Parsley Jun 12 – Nov 9
- Thyme Jun 12 – Nov 9
- Cabbage Jun 13 – Jul 27
- Green onions Jun 13 – Aug 9
- Dill Jun 14 – Aug 9
- Broccoli Jun 15 – Jul 31
- Swiss chard Jun 17 – Oct 12
- Marigolds (in bloom) Jun 18 – Sep 28
- Oregano Jun 19 – Nov 6
- Carrots Jun 20 – Aug 14
- Cauliflower Jun 22 – Jul 31
- Basil Jun 25 – Sep 28
- Potatoes Jun 28 – Sep 9
July
Sow for fall
- Zucchini Jul 6–20
- Peas Jul 6–20
- Carrots Jul 6–27
- Beets Jul 6–27
- Kale Jul 6 – Aug 3
- Collard greens Jul 6 – Aug 3
- Green onions Jul 13–27
- Cilantro Jul 20 – Aug 3
- Lettuce Jul 20 – Aug 10
- Kohlrabi Jul 20 – Aug 10
- Bok choy Jul 20 – Aug 10
- Spinach Jul 20 – Aug 17
- Turnips Jul 20 – Aug 17
- Arugula Jul 27 – Aug 24
- Mustard greens Jul 27 – Aug 24
Start picking
- Zucchini Jul 3 – Sep 28
- Nasturtiums (in bloom) Jul 3 – Sep 28
- Sage Jul 4 – Nov 9
- Cucumbers Jul 8 – Sep 28
- Green beans Jul 8 – Sep 28
- Lavender Jul 11 – Sep 5
- Rosemary Jul 11 – Oct 12
- Shallots Jul 13 – Aug 16
- Onions Jul 13 – Aug 26
- Garlic Jul 14 – Aug 4
- Okra Jul 15 – Sep 28
- Tomatoes Jul 18 – Sep 28
- Zinnias (in bloom) Jul 18 – Sep 28
- Cosmos (in bloom) Jul 18 – Sep 28
- Leeks Jul 20 – Nov 9
- Sunflowers (in bloom) Jul 21 – Sep 17
- Sweet corn Jul 23 – Sep 7
- Tomatillos Jul 23 – Sep 28
- Peppers Jul 25 – Sep 28
- Eggplant Jul 30 – Sep 28
August
Sow for fall
- Radishes Aug 10–31
Start picking
- Cantaloupes Aug 4 – Sep 8
- Watermelons Aug 4 – Sep 17
- Hot peppers Aug 4 – Sep 28
- Winter squash Aug 7 – Sep 28
- Celery Aug 12 – Oct 7
- Pumpkins Aug 17 – Sep 28
- Beets Aug 25 – Sep 29
- Arugula Aug 26 – Oct 3
- Mustard greens Aug 26 – Oct 8
- Cabbage Aug 28 – Oct 25
- Bok choy Aug 29 – Oct 4
- Spinach Aug 29 – Oct 6
- Lettuce Aug 29 – Oct 10
- Turnips Aug 29 – Oct 16
- Peas Aug 30 – Sep 28
- Cauliflower Aug 30 – Oct 12
- Broccoli Aug 30 – Oct 22
- Sweet potatoes Aug 31 – Sep 28
September
Sow for fall
- Garlic (garlic cloves) Sep 14 – Oct 19
Start picking
- Brussels sprouts Sep 1 – Nov 9
- Kohlrabi Sep 3 – Oct 9
- Cilantro Sep 3 – Oct 12
- Radishes Sep 4–30
- Carrots Sep 4 – Oct 16
- Green onions Sep 11 – Oct 23
- Parsnips Sep 14 – Nov 9
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.