When to Plant Marigolds

The rule: after frost, into warm soil

Marigolds are warm-season annuals, and a frost kills them. The safe outdoor planting time is after your average last spring frost, which is shown with the dates for your zone above. The same timing works for transplants and for seed sown directly in the bed.

Soil warmth matters as much as the calendar. Clemson germinates seed at 70 to 75°F, and Mississippi State gives 75 to 80°F for outdoor sowings, where seed comes up in 4 to 7 days. In cold soil the seed just sits there. If a late spring stays chilly, waiting a week or two past the frost date usually gets plants off to a quicker start.

Starting indoors: count back from your frost date

Indoor sowing gets flowers weeks earlier than direct sowing. Extension guides give slightly different lead times:

• Mississippi State: 4 weeks before the last frost, for plug-grown plants.
• Iowa State: 6 weeks.
• Clemson: 4 to 6 weeks for most types and 8 weeks for African marigolds.

Use the longer end for African types and the shorter end for compact French and signet varieties, which bloom quickly. Seedlings held indoors too long get leggy and root-bound, so it’s better to sow on time than early. Harden plants off for a few days before you set them out.

Plant African marigolds first

Tall African marigolds take longest to reach full bloom, so Penn State recommends getting them in right after frost danger has passed. Mississippi State notes that its Giant series of tall cut-flower African marigolds takes 70 to 90 days to reach its full 36- to 40-inch height. A late planting may barely flower before fall.

French and signet marigolds are more forgiving. Penn State says they can be planted any time from spring through midsummer.

How late can you plant?

Work backward from your first fall frost. The University of Arizona’s low-desert chart gives 30 to 60 days from seed to bloom for both African and French marigolds, and Penn State says flowering typically begins about two months after sowing. A sowing made at least two to three months before your first fall frost will give a worthwhile show. Closer to frost, buy transplants already in bud.

Midsummer sowings in the South have to cope with heat. Mississippi State notes that plants can stall during peak July-August heat, so keep late seedlings watered until they’re established. Around San Antonio, Texas A&M AgriLife lists May as still fine for sowing marigold seed directly in the ground.

Warm-winter regions

Where frost is rare, the calendar shifts:

• Florida: UF/IFAS lists marigolds for planting from spring into early summer and again in September. South Florida also has November and an earlier start in February. French types are reliable year-round there, while large African types are best planted for spring bloom.
• Arizona low desert (Phoenix area): The University of Arizona chart shows African marigolds planted from February to early June and French marigolds from February to May. French types also get a second planting in September, which blooms through fall into winter.

In both places the hottest months are the ones to skip for new plantings. Marigolds tolerate heat once established, but seedlings set out in peak summer struggle.