Zone 3a Planting Calendar
In zone 3a, the median last spring frost falls around May 30 and the first fall frost around Sep 12, giving roughly 104 frost-free days. Average annual minimum temperature is -40°F to -35°F. Every date in the table below is calculated from those two frost dates.
Comparable areas: International Falls, MN, Gunnison, CO, Havre, MT. Split between far-northern continental interiors (northern MN, northern ME, north-central ND/MT) and high-elevation valleys of the Intermountain West. The two behave very differently: mountain-valley 3a sites such as Gunnison, CO can record frost in any month and have frost-free seasons under 80 days, well short of the ~105 days shown here. Treat this row as a floor, not a promise.
What to plant and when in zone 3a
Sorted by when you start each crop. Dates are calculated from a median last frost of May 30 and a first frost of Sep 12.
| Crop | Start indoors | Plant outside | Fall sowing | Harvest from |
|---|---|---|---|---|
| Celery | Mar 7 – Mar 21 | Jun 13 – Jun 26 | — | Sep 21 – Oct 21 |
| Leek | Mar 7 – Apr 4 | May 2 – May 15 | — | Jul 31 – Sep 29 |
| Onion | Mar 7 – Mar 21 | May 9 – May 22 | — | Aug 17 – Sep 6 |
| Rosemary | Mar 7 – Mar 21 | Jun 13 – Jun 26 | — | Sep 1 – Sep 21 |
| Kale | Mar 14 – Apr 4 | May 2 – May 15 | Jun 20 – Jul 3 | Jun 21 – Jul 23 |
| Broccoli | Mar 21 – Apr 11 | May 9 – May 22 | Jun 13 – Jun 26 | Jun 28 – Aug 7 |
| Cabbage | Mar 21 – Apr 11 | May 9 – May 22 | Jun 13 – Jun 26 | Jul 8 – Aug 17 |
| Pepper (sweet/bell) | Mar 21 – Apr 18 | Jun 20 – Jul 3 | — | Aug 29 – Sep 13 |
| Chives | Mar 21 – Apr 4 | May 30 – Jun 12 | — | Aug 18 – Aug 28 |
| Common Thyme | Mar 21 – Apr 4 | May 30 – Jun 12 | — | Jul 29 – Aug 28 |
| Greek Oregano | Mar 21 – Apr 4 | May 30 – Jun 12 | — | Aug 18 – Aug 28 |
| Cauliflower | Mar 28 – Apr 18 | May 16 – May 29 | Jun 13 – Jun 26 | Jul 5 – Aug 4 |
| Eggplant | Apr 4 – Apr 18 | Jun 13 – Jun 26 | — | Aug 7 – Sep 1 |
| Sweet Potato | Apr 4 – Apr 18 | Jun 20 – Jul 3 | — | Sep 18 – Oct 18 |
| Basil | Apr 4 – Apr 18 | Jun 6 – Jun 19 | — | Aug 12 – Sep 11 |
| Garden Sage | Apr 4 – Apr 18 | May 30 – Jun 12 | — | Aug 8 – Aug 18 |
| Parsley | Apr 4 – Apr 18 | May 30 – Jun 12 | Jul 4 – Jul 17 | Aug 8 – Aug 18 |
| Spearmint | Apr 4 – Apr 18 | May 30 – Jun 12 | — | Jul 29 – Aug 28 |
| Calendula / Pot Marigold | Apr 4 – Apr 18 | May 16 – May 29 | Jul 18 – Jul 31 | Jul 5 – Jul 15 |
| French Marigold | Apr 4 – May 2 | Jun 6 – Jun 19 | — | Jul 21 – Aug 5 |
| Sweet Alyssum | Apr 4 – Apr 18 | May 16 – May 29 | Jul 18 – Jul 31 | Jun 27 – Jul 11 |
| Tomato | Apr 11 – Apr 25 | Jun 6 – Jun 19 | — | Jul 31 – Sep 4 |
| Bok Choy | Apr 18 – May 2 | May 16 – May 29 | Jul 18 – Jul 31 | Jun 15 – Jul 15 |
| Collard Greens | Apr 18 – May 2 | May 16 – May 29 | Jun 20 – Jul 3 | Jul 15 – Aug 4 |
| Kohlrabi | Apr 18 – May 2 | May 9 – May 22 | Jul 11 – Jul 24 | Jul 5 – Jul 15 |
| Lettuce | Apr 18 – May 2 | May 9 – May 22 | Jul 4 – Jul 17 | Jul 5 – Jul 25 |
| Spinach | Apr 18 – Apr 25 | May 9 – May 22 | Jul 25 – Aug 7 | Jul 6 – Jul 17 |
| Swiss Chard | Apr 18 – May 2 | May 16 – May 29 | Aug 15 – Aug 28 | Jun 25 – Jul 10 |
| Pea | — | Apr 25 – May 8 | Jul 11 – Jul 24 | Jun 19 – Jul 9 |
| Rhubarb | — | Apr 25 – May 8 | — | Apr 24 |
| Watermelon | Apr 25 – May 16 | Jun 13 – Jun 26 | — | Aug 22 – Sep 16 |
| Arugula | — | May 2 – May 15 | Aug 1 – Aug 14 | Jun 1 – Jun 21 |
| Asparagus | — | May 2 – May 15 | — | May 1 |
| Cucumber | May 2 – May 16 | Jun 13 – Jun 26 | — | Aug 2 – Aug 22 |
| Pumpkin | May 2 – May 9 | Jun 13 – Jun 26 | — | Sep 6 – Oct 11 |
| Turnip | — | May 2 – May 15 | Jul 11 – Jul 24 | Jun 11 – Jul 16 |
| Nasturtium | May 2 – May 9 | Jun 6 – Jun 19 | — | Jul 31 – Aug 10 |
| Beet | — | May 9 – May 22 | Jul 4 – Jul 17 | Jun 28 – Jul 18 |
| Carrot | — | May 9 – May 22 | Jun 27 – Jul 10 | Jul 8 – Jul 28 |
| Potato | — | May 9 – May 22 | — | Jul 18 – Sep 6 |
| Radish | — | May 9 – May 22 | Aug 1 – Aug 14 | May 30 – Jun 23 |
| Sunflower | May 9 – May 16 | Jun 6 – Jun 19 | — | Aug 15 – Sep 14 |
| Parsnip | — | May 16 – May 29 | — | Sep 3 – Sep 23 |
| Winter Squash (Butternut) | May 16 – May 23 | Jun 13 – Jun 26 | — | Sep 1 – Sep 21 |
| Cantaloupe (Muskmelon) | May 16 – May 23 | Jun 13 – Jun 26 | — | Aug 20 – Sep 6 |
| Strawberry | — | May 16 – May 29 | — | Jun 13 – Jun 15 |
| Dill | — | May 23 – Jun 5 | Jul 4 – Jul 17 | Jul 2 – Jul 17 |
| Bush bean | — | May 30 – Jun 12 | Jul 4 – Jul 17 | Jul 19 – Jul 29 |
| Pole bean | — | May 30 – Jun 12 | — | Jul 27 – Aug 1 |
| Sweet corn | — | May 30 – Jun 12 | — | Jul 29 – Sep 7 |
| Borage | — | May 30 – Jun 12 | — | Jul 19 – Jul 29 |
| Cilantro / Coriander | — | May 30 – Jun 12 | Jul 18 – Jul 31 | Jul 14 – Aug 8 |
| Brussels Sprouts | — | Aug 8 – Aug 21 | Jun 6 – Jun 19 | Nov 1 – Nov 26 |
| Summer squash / zucchini | — | Jun 6 – Jun 19 | — | Jul 11 – Jul 31 |
| Okra | — | Jun 13 – Jun 26 | — | Aug 12 – Aug 22 |
| Garlic | — | — | Sep 12 – Sep 25 | — |
Print this page for a calendar you can pin up in the shed.
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One zone is not one climate. USDA hardiness zones are drawn from average winter minimum temperature and nothing else, so they do not determine frost dates. Two gardens in zone 3a can differ by two or three weeks depending on elevation, distance from water, and local topography. Treat this page as a starting schedule and adjust it to what your own garden has actually done. How these dates were derived →
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