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When to plant Cosmos

Computed from land-grant Extension planting-window rules (cited below), localized to real ZIP-level median frost dates, not a single national guess. These are national-generic rules by hardiness class; individual state Extension offices layer their own regional adjustment on top (earlier in the Deep South, later in the Upper Midwest). Enter your ZIP for your own dates, or read the four representative locations below.

Planting windows and crop timing here are computed from USDA/NOAA climate data and the university extension sources cited below, not a site visit or soil test. Treat this as a starting point: local conditions vary, and a local nursery or extension office can advise on your exact site. See our full Disclaimer.

Representative timing, by climate band

When to plant Cosmos in four US climates

Each column is the most nursery-dense location in our directory within that USDA zone band, computed from that location's own real median frost dates, not a made-up example.

Stage Zones 1-5 (cold winters)
Fort Plain, NY 		Zones 6-7 (temperate)
McMinnville, TN 		Zones 8-9 (warm)
Apopka, FL 		Zones 10-13 (hot, frost rare or absent)
Loxahatchee, FL
Start seed indoors Not available Not available Not available –
Direct-sow outside May 6–May 20 Apr 7–Apr 21 Feb 24–Mar 10 –
Transplant outside Not available Not available Not available –
Fall planting Not available Not available Not available –
Expected harvest Not available Not available Not available –

Zones 10-13 (hot, frost rare or absent) (Loxahatchee, FL): Frost is rare here (about 359 frost-free days a year); most years see little or no hard freeze. This is a tender crop. In climates like this one, tender and very-tender crops typically go in before the hottest months arrive, not on a frost-relative schedule.

Cosmos is classified tender here, though one reading of one source disagrees: an internal comparison of Clemson Cooperative Extension's Growing Annuals factsheet leaned toward calling cosmos hardy, reasoning that it self-seeds year after year. Self-seeding from winter-dormant seed isn't the same as frost-hardy foliage, and Clemson's own factsheet elsewhere treats cosmos alongside other tender bedding annuals.

NC State Extension's Plant Toolbox is explicit and unambiguous: cosmos is a "tender annual, not frost-hardy," sown outdoors "after the danger of frost is past and when the soil has warmed to at least 65 degrees." Missouri Botanical Garden's Gardening with Annuals factsheet groups Cosmos sulphureus under its Summer (tender) Annuals table as well. This page follows NC State's explicit, directly quoted rule, including its 65°F soil-temperature figure.

Cosmos is grown from seed, direct-sown once soil has warmed past that mark.

Frost hardiness

Tender. Damaged or killed by frost. Plant after the last frost date.

Minimum soil temperature

65°F

For direct sowing/germination, where an Extension source stated it.

Sourcing notes

DISAGREEMENT: Clemson's Growing Annuals factsheet content (as classified in an internal comparison table) leaned toward calling cosmos "hardy," reasoning it can self-seed year after year -- but self-seeding via winter-dormant seed is not equivalent to the foliage being frost-hardy, and Clemson's own factsheet elsewhere treats cosmos alongside other tender bedding annuals. NC State Extension Plant Toolbox is explicit and unambiguous: cosmos is a "tender annual, not frost-hardy," sown outdoors "after the danger of frost is past and when the soil has warmed to at least 65 degrees." Missouri Botanical Garden's Gardening with Annuals factsheet also groups Cosmos sulphureus under its Summer (tender) Annuals table. Classified tender per the more explicit, directly-quoted NC State source; min_soil_temp_f=65F is NC State-sourced.

Related crops

Growing zones for this crop

Nurseries near these locations

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Sources