When to Plant Green Beans

Spring: go by soil temperature

Beans are frost-tender, but the bigger danger at planting is cold soil. Utah State says bean seed needs soil above 60°F and germinates poorly below it. UC Cooperative Extension’s germination table shows how much warmth speeds things up: about 16 days to emergence at 59°F, 11 days at 68°F, 8 days at 77°F and 6 days at 86°F. Seed that sits in cold, wet soil is prone to rot and damping off.

That is why the advice is “after frost and in warm soil” rather than a fixed date. The dates for your zone above give the usual window; a soil thermometer at planting depth tells you whether this particular spring is ready.

Sources differ on how hard to push the start. Maryland Extension says to wait until frost danger has passed. Utah State allows sowing from about a week before the frost-free date, and 2-3 weeks before it if you plant through plastic mulch or under fabric row covers, which warm the soil and give some frost protection. Maryland also suggests pre-sprouting seed before planting in cool spring soil to reduce rot and seed maggot problems.

Keep sowing for a steady supply

Bush beans bear for only about 2-3 weeks, so a single sowing gives one burst of beans. For a steady supply, sow a short row of bush beans every 2-3 weeks. Utah State continues until mid-July and Maryland through mid- to late July.

Pole beans bear for 5-6 weeks or longer if you keep picking, so Utah State notes that one or two plantings a year are usually enough.

Fall: count back from the first frost

A fall crop has to mature before frost kills the plants, and it grows more slowly as days shorten. Virginia Cooperative Extension’s fall-garden method accounts for both: take the variety’s days to maturity, add about 2 weeks for slower fall growth, and add 2 more weeks because frost-tender crops like beans need to mature before frost to give a reasonable harvest. For a 50- to 60-day bush bean, that means sowing roughly 11-12 weeks before your average first frost.

Purdue Extension’s fall table, which counts 50 days for bush beans, lists August 15 as the last feasible sowing date in northern Indiana and August 25 in southern Indiana. That is a little later than the Virginia method gives, so treat late sowings as a gamble on a mild autumn. Use the fastest bush variety you can find.

Late-summer sowings face hot soil. Purdue suggests a light mulch of compost, vermiculite or potting soil over the seed row to keep a crust from forming, and planting slightly deeper than in spring, where the soil is a little cooler.

Hot climates: two seasons, not one

Where summers are long and hot, beans are planted in spring and again in late summer, skipping the peak of summer, when heat above about 95°F makes the plants drop their flowers.

UF/IFAS lists March-April and August-September for North Florida, February-April and August-September for Central Florida, and September through April for frost-free South Florida. The University of Arizona’s Maricopa County calendar for snap beans in the Phoenix area runs from mid-March through April and again from mid-July through early September.

In Hawaii, UH CTAHR says beans grow well in the warm climate and are ready about 6 weeks after planting, but gives no planting months.