When to Plant Wildflower Seeds: Fall, Winter and Spring Dates Where You Live

Plant wildflower seeds in late fall or winter in most of the US: where winters are cold, sow after the first hard frost and before the ground freezes, so the seed lies dormant and sprouts in spring. In Texas, Florida and Southern California, sow earlier, from September to November (into January in central and south Florida), so seedlings grow over winter. Spring sowing also works, but seeds that need cold often wait a year to sprout.^4,13,17,18

We dated the fall window for 24 cities from NOAA’s 1991–2020 normals. The first 28°F hard freeze, when dormant sowing can start, comes around Oct 27 in Minneapolis, Nov 15 in Chicago and Nov 20 in Atlanta. Seeds that need 60 days of cold must be down by Feb 24, Feb 10 and Jan 2.¹ We also tested two common rules against our data, and checked published calendars from seven sources for 14 places.

Dormant, fall or spring: the three sowing seasons

The sources describe three sowing seasons; which one fits depends on your winter:

Sources: Prairie Moon Nursery,^4,6 the University of Minnesota (prairie seed),¹⁰ the University of Maine,²⁷ Illinois DNR,¹¹ the Xerces Society,⁸ TxDOT,¹³ Texas A&M,¹⁴ South Carolina NRCS,¹⁵ the Florida Wildflower Foundation¹⁷ and the Theodore Payne Foundation.¹⁸ Prairie Moon, a Minnesota native-seed nursery, puts it simply:

Late fall (after a hard frost) is the optimal time for outdoor seedings.

Fall works because most native wildflowers need a winter to break dormancy.⁹ Prairie Moon codes seeds that need cold, moist treatment as C(30) or C(60), for 30 or 60 days, which it gives at 33–40°F in a refrigerator; sown outdoors in late fall, winter does it for you.⁵ Minnesota’s Board of Water and Soil Resources lists exceptions that need no cold, such as wild bergamot, evening primrose, mountain mint and asters, which can be sown in spring or fall.⁹ For sowing in covered containers instead of the ground, see our winter sowing guide.

Dormant sowing dates by city

For each city we took two dates from the NOAA station nearest its ZIP code. Dormant sowing opens at the median first hard freeze, 28°F, the National Weather Service’s definition.³ The deadline for seeds that need 60 days of cold is the last date that still leaves 60 nights at 40°F or colder before spring, counted exactly as in our winter sowing guide, so the two pages agree.^1,5

The window shrinks to the south. Minneapolis opens Oct 27 and runs to Feb 24, about four months; Atlanta opens Nov 20 and closes for 60-day seeds Jan 2; Portland, Oregon, gets two weeks. Dallas averages 48 cold nights, enough only for 30-day seeds, and Austin, San Antonio and Houston have no normal night at 40°F or colder, so seed sown there gets little natural cold; Texas sources sow from September instead (below). Gardens far from a station can differ, so look up your own frost and hard-freeze dates.

Two common rules, tested

“Sow after a killing frost”

A killing frost has no fixed temperature, as our frost vs. freeze guide explains, and the advice varies: after two or three killing frosts, after the first few, or after a hard frost.^19,20,4 Across 36,955 ZIP codes, the median hard freeze follows the median first 32°F frost by 11 days (middle 80%: 9–15 days).¹ Either way, the goal is seed that stays dormant: Prairie Moon warns that grass seed sown before mid-October in the Upper Midwest can sprout within ten days in warm weather and be winter-killed.⁶

“Sow 8 weeks before your first frost” in zones 7–10

The National Garden Bureau advises an active fall sowing at least 8 weeks before the first frost in mild-winter zones 7 to 10, and a dormant sowing in zones 1 to 6; American Meadows gives the same two-month rule for warm climates, and Google’s AI Overview repeats the split.^20,19

In the 13 cities in zones 7 to 9 outside Texas, eight weeks before the median first frost falls between Sep 1 and Oct 6, with normal highs of 66–85°F: an active sowing like South Carolina’s. That can work, but the zone line misplaces the switch. A sowing on the median hard-freeze date still gets 60 cold nights in 100% of ZIP codes through zone 8a, 86% of 8b, 28% of 9a and 8% of 9b.^1,2 In 38% of 9b and 95% of 10a ZIP codes there is no normal hard freeze to wait for.

Hardiness zones measure the coldest night of the year, not the length of winter, so a zone can’t date this.²¹ To check yours, use our zone lookup by ZIP code.

Published calendars against the NOAA dates

We checked published fall windows from seven sources against the NOAA dates for 14 places they cover:

None of these windows waits for a killing frost. Prairie Moon’s mid-October start comes closest, 4 days before Winona’s median first frost and 14 before its hard freeze; Illinois DNR starts September 15, 37 days before Springfield’s first frost, and says the seeds won’t sprout until spring.^6,11 In the South, agencies aim to finish before frost. South Carolina NRCS wants fall planting done at least six weeks before hard-freezing weather, by October 10 in the Piedmont; Greenville’s median hard freeze comes 43 days later, a match.¹⁵

Texas, Florida and California

TxDOT sows from September 1 through the end of November for most of Texas, and bluebonnets in late summer or early fall.¹³ That window closes 1 day after Dallas’s median first frost but 24 days after Amarillo’s hard freeze, and Texas A&M’s Michael Arnold adds:

The farther north you are in Texas, then the earlier you should plant.

Florida’s windows run mid-September to late October in the north, mid-October to early January in central Florida and November to mid-January in the south, set by soil warmth and rain rather than frost; germination drops as soil cools below the mid-60s.¹⁷ Orlando and Miami have no normal frost. In Los Angeles, the Theodore Payne Foundation sows annual wildflowers from mid-October through late November, so seed sprouts with the fall rains.¹⁸ In Colorado, NRCS asks dormant seedings to get at least 45 days of soil at 45°F or colder.¹⁶

Spring sowing: what you give up

Sown on the median last-frost date, seed gets a median of 0 cold nights in every hardiness zone, and 9 at most in our 24 cities.¹ Seeds that need cold mostly sit out the first summer: Prairie Moon lists a one-year delay for those species, and Illinois DNR says some won’t germinate until the second year.^6,11

Spring does give time to clear weeds, and it suits warm-season grasses.⁶ To sow cold-needing seed in spring, chill it first: Oklahoma State Extension gives four to eight weeks in a moist medium in the refrigerator, and Prairie Moon 33–40°F.^12,5 See what a last frost date means.

Site prep, seeding rates and sowing

Prairie Moon, UMN, Illinois DNR and Oklahoma State all start by removing the existing vegetation; Prairie Moon lists smothering, sod removal, repeated shallow tilling or herbicide, and gives a weedy site a full season or two.^6,7,10,11,12 TxDOT is the outlier: it says most seed can go on undisturbed soil, with some delay, as long as it touches the soil.¹³ Follow the label on any herbicide. Rates and carriers vary by source:

Pure live seed is purity times germination rate, figures the supplier provides.¹³ Prairie Moon’s rule of thumb is to sow no deeper than the seed is wide.⁵ Divide the seed and the area into equal parts and broadcast each part; Prairie Moon compares it to sowing lawn seed.^6,7,12 Turf grass is a different crop with its own cue; see dormant seeding a lawn.

What to expect after sowing

Texas A&M notes that annuals bloom the first year while perennials do better in the second or third.¹⁴ Illinois DNR expects most of its native mix to bloom in year two or three, and UMN says seeded wildflowers take two to five years.^11,10 First-year weeds outgrow the seedlings, so Prairie Moon mows to 4–5 inches whenever weeds reach 8–10 inches.⁷

Next step: find your ZIP code’s first frost and hard freeze in our frost date lookup, then see our other flower and bulb planting guides.