Zone 4 Planting Calendar (4a & 4b): Printable, by Month

Zone 4 is conventionally taken to average its last spring frost around May 10 and its first fall frost around September 25, giving roughly 138 frost-free days. Be aware that a hardiness zone is defined by winter minimum temperature, not by frost dates — these are widely-used approximations, not official USDA figures. Get your real dates from the NOAA freeze-date map or your county cooperative extension office.

Use the month-by-month table on this page. The pattern is: frost-tolerant crops like peas, spinach and radishes go in 6 to 2 weeks before May 10; warm-season crops like beans, zucchini and tomatoes go in 1 to 3 weeks after it; and cool-season crops get a second sowing about 10 to 12 weeks before September 25.

Yes. In zone 4, start tomato seed indoors 6 to 8 weeks before May 10 or buy a seedling, then transplant 1 to 2 weeks after the last frost once nights stay above 50°F. With 138 frost-free days there is enough season for early and mid-season varieties, though large beefsteak types are a gamble — choose cherry or early varieties rated under 70 days.

One main round plus a tight fall sowing of the fastest crops. Radishes, spinach and lettuce can still be squeezed in after an early crop comes out.

Yes, in spring. A raised bed warms 2 to 3 weeks earlier than open ground, so you can bring the early sowings forward by up to two weeks. Autumn dates are unchanged, since the first frost arrives on the same day regardless of your setup.

Five degrees in the average coldest night of the year. Zone 4a averages -30 to -25°F at its coldest and zone 4b -25 to -20°F. The letter matters for perennials on the edge of winter hardiness. It does not change vegetable planting dates, which follow your frost dates — the calendar on this page applies to both halves.

Neither — the letter does not decide it. 4a and 4b differ only in how cold the coldest winter night gets, and tomatoes grow in summer, long after that night has passed. What matters is the length of your frost-free season. Within zone 4, Rochester, MN (4b) averages 159 frost-free days and Great Falls, MT (4b) only 126. Check the city table on this page, or enter your own frost dates in the calendar.

In zone 4, July plantings are: sow for a fall crop — kale, lettuce (leaf), peas, radish and spinach; re-sow every 14 days — bush beans, kale, lettuce (leaf), radish and spinach. The July table gives the exact window for each. Cool-season sowings in July may bolt in the heat.

Sowings for a fall harvest in zone 4 start around June 9 with carrot and run to about August 12 with radish. Each date is counted back from the average first frost (September 25) by the crop's days to harvest plus two weeks, so a crop sown on time matures before the cold arrives. That puts the slowest crops in before midsummer: with the first frost in September, a fall carrot crop has to be sown while it still feels like spring.

Not as a download yet. The chart and the month-by-month tables on this page print cleanly — use your browser's Print command and the menus, ads and questions are left off the page. A downloadable version is on the way.