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When to plant Four O'Clock

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.

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Representative timing, by climate band

When to plant Four O'Clock 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.

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.

Four o'clock (Mirabilis jalapa) is a tender annual across nearly all of this site's range. NC State Extension's Plant Toolbox rates it hardy only in USDA zones 9a through 10b as a tuberous perennial, and calls it, in its own words, "grown as an annual" everywhere colder, including NC State's home state of North Carolina, where frost kills the plant back. Clemson Cooperative Extension's Growing Annuals factsheet and Missouri Botanical Garden's Gardening with Annuals both corroborate that tender, summer-annual read.

Outside zones 9a-10b, NC State describes an overwintering option for the plant itself, not the foliage: dig the tuberous roots before the first fall freeze and store them to replant the following spring, the same tuber-saving approach gardeners use for dahlias and cannas, rather than a fall-sowing technique.

Plant after your last frost; NC State recommends soaking seed overnight to speed germination. No extension source in our records gives a specific first-bloom day count, so that field is blank. Four o'clock is bought as seed; the perennial-zone tuber trade mostly runs through gardeners saving their own stock rather than nursery stock.

Sourcing notes

Tender annual across most of the U.S.: NC State Extension Plant Toolbox rates Mirabilis jalapa hardy only in USDA zones 9a-10b as a tuberous perennial; in colder regions (including NC State's own North Carolina) it is "grown as an annual" and killed by frost, with tuberous roots optionally dug before the first fall freeze and stored/replanted (a perennializing technique, not a fall-sow annual technique). Clemson Growing Annuals and Missouri Botanical Garden's Gardening with Annuals both corroborate the tender/summer-annual classification. NC State recommends soaking seed overnight to speed germination and planting after last frost; no extension source gave a specific first-bloom day count, so days_to_maturity is left blank.

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Sources

• Clemson Cooperative Extension Home & Garden Information Center, Growing Annuals (HGIC 1152) (accessed 2026-08-04)
• Missouri Botanical Garden (Kemper Center for Home Gardening / gardeninghelp.org), Gardening with Annuals (accessed 2026-08-04)
• NC State Extension Gardener Plant Toolbox, Mirabilis jalapa (accessed 2026-08-04)