When to Plant Green Beans: Wait for 60°F Soil, Not Just Frost

Sow green beans outdoors after your last frost and once the soil has warmed to about 60°F, then keep sowing every 2 to 3 weeks until roughly 78 days before your first fall frost. The two spring limits are not the same date: on the median last-frost date the normal air temperature is still under 60°F in 98.4% of US ZIP codes, a gap with a median of 19 days. In Chicago that makes the first sowing May 11 and the last bush bean sowing August 19; in Dallas it is March 17 to April 21, then August 2 to September 12.

Beans are frost-tender, direct-sown and quick, so the usual “weeks before frost” rule does not fit them. We combined the soil, heat and days-to-maturity rules of eight extension sources with NOAA 1991–2020 normals¹ for 37,563 lower-48 ZIP codes and built dates for 22 cities. Everything uses air temperature as a stand-in for soil temperature, because our NOAA data has no soil readings.

Spring: the soil date comes after the last frost

Every source says to wait for frost to pass. The Old Farmer’s Almanac says to sow any time after the last spring frost date, once soil is at least 55°F,² Iowa State puts the start around May 10 in central Iowa,³ and Utah State starts a week before the last frost-free date.⁵ Google’s AI Overview for this query said to wait roughly 1 to 2 weeks after the last frost when we checked on October 14, 2026. Soil is the stricter test, and Clemson is blunt about it:

Do not plant beans before the soil temperature is at least 60 ºF

Each window below opens on the later of two dates: the median last 32°F frost, or the day the normal daily mean air temperature reaches 60°F. Clemson, Utah State and Maryland use 60°F,^4,5,7 and the Almanac, Georgia and Penn State use 55°F.^2,9,8

On the median last-frost date the normal air mean is under 60°F in 98.4% of ZIP codes and under 55°F in 62.0%. A week later it is still under 60°F in 94.0%, and two weeks later in 74.6% (under 55°F in 10.7%). The median wait after the last frost is 19 days, and 78.4% of ZIP codes wait 14 days or more. Boston waits 47 days and Portland 89, because maritime springs stay cool long after the last frost.

Waiting for 60°F also covers most frost risk. The median last frost is a 50% date, but in 66.2% of ZIP codes the 60°F date falls on or after the date with only a 1-in-10 chance of a later frost, so beans sown then rarely meet frost. Where frost is the later limit, as in Austin and Gainesville, the median last frost sets the date, and our frost-cover guide lists beans among the tender crops to cover first.

Soil, air and seed: the rules compared

The sources agree on the shape and differ on the numbers. Utah State says seedlings emerge in 7 to 10 days in soil that has warmed to 65 to 85°F and that germination is greatly reduced below 60°F,⁵ Washington State waits for 65°F,¹¹ and the Almanac warns that cold, moist soil delays germination and can rot seed.² The table sets the rules side by side and the chart puts them on one scale.

Sow seed in the ground. The Almanac says beans grow best direct-seeded because their fragile roots may not survive transplanting.² Washington State allows seedlings started indoors 10 days to 2 weeks before they go out,¹¹ and Seed Savers says no more than 3 to 4 weeks.¹² Our seed-starting guide covers the crops that do benefit from an indoor start.

Sowing earlier: thermometer, mulch and covers

A soil thermometer settles the argument that air averages cannot. Maryland points out that beans, cucumbers and melons need soil of at least 60°F to germinate and that cool, wet soil slows germination and invites rot.⁷ It adds that pre-germinating seed before planting in cool spring soil may help prevent soil rot and seed maggot problems.⁶ If you want a head start, Utah State says plastic mulch can give some frost protection and allow earlier planting and maturity, and that with plastic or row covers you can plant 2 to 3 weeks before the last frost date.⁵ Treat that as a gamble on a cold snap: the soil rule above still applies under the cover.

Heat: when the flowers drop

Beans are warm-season, but too much heat costs pods. Iowa State says hot, dry conditions during blossoming can strip the plant:³

may cause many of the flowers to drop off without setting pods

The lines differ: Georgia says air above 85°F can cause flowers to drop,⁹ Clemson says blossom drop may be a problem above 90°F,⁴ and Utah State says above 95°F with dry conditions.⁵ We used 90°F applied to the normal daily high, which reaches 90°F somewhere in the year in 27.3% of ZIP codes (59.3% at 85°F, 6.5% at 95°F).

Timing matters because flowers open weeks after sowing. Utah State gives 50 to 60 days to maturity and pods 7 to 14 days after flowering,⁵ which puts the first flowers 36 to 53 days after sowing; we use the midpoint, 45 days (our derivation). A sowing is flagged when its flowers would open after the normal high reaches 90°F. In the 10,236 ZIP codes that reach it, that leaves a pause between the last spring sowing and a late-summer restart: a median of 67 days, and 30 days or more in 83.8%. Dallas, for example, sows March 17 to April 21 and restarts August 2.

Treat a flagged pause as a warning, not a ban. Utah State sows straight through to mid-July,⁵ and mulch and even watering help during flowering. If you sow in the gap, choose varieties that tolerate heat and keep the soil evenly moist.

Succession sowing and the last sowing date

Bush beans crop in a rush: Maryland says harvest slows or stops after 3 to 4 weeks,⁷ and Utah State puts it at 2 to 3 weeks for bush types.⁵ Hence the advice to sow a new row on a schedule:

Plant bush beans every 14-21 days until mid-July

Clemson says 10 to 14 days,⁴ the Almanac and Penn State two weeks,^2,8 and Iowa State and Maryland 2 to 3 weeks.^3,6 At 14 days the median ZIP code gets 6 sowings; at 21 days, 4, with a range from none to 18 at 14 days. The last sowing counts back 78 days from the median first frost: 50 days to maturity (the low end of Utah State’s 50 to 60), 14 for slower fall growth and 14 more because beans are frost-tender, the same count as our fall vegetable planting guide. Chicago’s median first frost is November 5, and 78 days earlier is August 19. The median last bush sowing is August 7; by September 1 it has passed in 87.3% of ZIP codes, and in 33.2% it falls before August 1.

Other guides count differently. Gardener’s Path adds about two weeks to days to maturity, roughly 10 weeks before frost,¹³ and Our Stoney Acres counts back at least 70 days and says beans can be planted until about 80 days before the first frost.¹⁴ Google’s AI Overview for “when to plant green beans for fall harvest” said 10 to 12 weeks before the first frost when we checked on October 14, 2026. Ours is 78 days, 11 weeks, so it sits inside that spread. For pole beans Gardener’s Path adds about 30 days to days to maturity,¹³ where we add 28 to Georgia’s 65.¹⁰ Iowa State’s own last practical date for central Iowa, August 1, is within 2 days of ours for Des Moines.³

Bush or pole beans

Pole beans need longer to start bearing and then bear longer. Georgia lists 50 to 60 days for bush and 65 to 75 for pole,¹⁰ and Utah State says pole plants flower and mature pods for 5 to 6 weeks against 2 to 3 for bush, so one or two sowings are enough.⁵ Counting 65 + 14 + 14 = 93 days back from the first frost, the last pole sowing comes 15 days before the bush date: July 23 at the median, and before August 1 in 67.1% of ZIP codes. If you are planning tomatoes in the same bed, see when to plant tomatoes.

How published local calendars compare

Four extension sources publish dates we could convert. Iowa State’s and Georgia’s start and end dates land within a few days of ours; Maryland’s last date is 8 days earlier than ours; and Utah State’s start rule runs far ahead of the 60°F test in Salt Lake City, where our NOAA station’s median last frost is March 31.

Frost-free ZIP codes and Hawaii

Where the table has no median frost date, count months instead. The normal air mean is at least 60°F from March through November in Phoenix (ZIP 85001) and Los Angeles (90001), from July through October in San Francisco (94103) and all year in Miami (33101). Only Phoenix has normal monthly highs of 90°F or more, May through September. Our table has no frost dates for 104 of Hawaii’s 135 ZIP codes, so we give no Hawaii dates; ask your county extension office.

How we calculated these dates

Daily temperatures are NOAA’s monthly normals placed on the 15th of each month and interpolated linearly, for the station nearest each ZIP code.¹ Frost dates are the median 32°F dates. The 60°F and 90°F lines, the 45-day flowering lag and the 78- and 93-day counts are the published rules above, applied to air temperature, not soil. Individual years vary by weeks.

Next steps

Look up your own frost dates with our frost date lookup and read what a last frost date means. More crops are in our vegetable guides.