When to Plant Wildflowers

Why fall works

Many wildflower seeds won’t germinate until they have been through winter. Clemson explains that some species need 6 to 12 weeks of cool, moist conditions at around 40°F, called stratification, before they sprout. Sowing in fall lets winter provide that treatment. The seed lies dormant through the cold months and comes up in spring when conditions suit it.

Fall sowing has other advantages. Seedlings of hardy annuals and perennials use fall and winter rain and cool soil to get established. Clemson also notes that spring plantings can face more weed competition if the soil isn’t well prepared.

This kind of dormant seeding follows soil temperature, not the frost date, so use the regional windows below rather than counting weeks from a frost date.

Fall windows by region

Northern New England: UNH’s fall planting season runs from late September through early December, depending on the year. The safest target is mid-to-late October. In November, snow can arrive any day and cover the ground before you sow.

South Carolina: Clemson sows from September through November, as soil temperatures fall toward 40°F. This timing is ideal for wildflowers that bloom in spring and early summer.

Texas: Texas A&M recommends September, October or early November, so plants can establish before winter dormancy. Plant earlier the farther north you are in Texas.

Florida: UF/IFAS sets windows by region:

• North Florida: mid-September to mid-October
• Central Florida: mid-October through December
• South Florida: November through January

Arizona low desert: The University of Arizona’s planting guide puts cool-season flowers, including most of its wildflower species, in the ground in fall, for bloom through spring until heat arrives.

Plan backward from the sowing date

A fall sowing date really starts the previous spring. UNH and UF/IFAS both call for a full season of site preparation before seeding, so existing grass and weeds are dead when the seed goes down. UNH smothers vegetation under black plastic from mid-June to mid-September, which leaves a clean seedbed just in time for fall sowing. One method doesn’t fit this schedule: a summer cover crop such as buckwheat has to decompose before you sow, so UNH notes it generally rules out fall planting and pushes seeding to spring.

Order seed early, too. UNH suggests ordering in early summer to avoid shortages of popular mixes and storing it in the refrigerator until planting.

Sowing in spring instead

If fall slips by, sow in spring. UNH’s advice is to store seed cold and dry, at 35 to 40°F, over winter and sow as early in spring as possible, so the seed still gets some cool, moist weather. In South Carolina, Clemson gives March through late April as the spring window, provided seedlings get enough moisture.

Expect two drawbacks. Perennials sown in spring generally won’t flower until their second growing season, and weeds compete harder with spring plantings unless the site was well prepared. Annual wildflowers handle spring sowing best: Clemson notes they germinate promptly and establish quickly when sown in spring after the threat of frost. A spring sowing of a mix with plenty of annuals still gives color the first summer.

After sowing

Whatever the season, keep the seedbed moist for the first 4 to 6 weeks of germination and early growth. Sowing just before your area’s normal seasonal rains saves most of the watering.