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When to plant Larkspur

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 Larkspur 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 Not available Not available Not available –
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 hardy crop. In climates like this one, hardy and semi-hardy crops typically go in during the cooler months (fall through late winter), not on a frost-relative schedule.

Larkspur runs on an atypical temperature rule, and one source has tested it directly. Cornell University's High Tunnels program states larkspur seed requires low temperatures to germinate and "does not germinate well above 65°F," with a two-week refrigerated cold treatment improving germination. Clemson Cooperative Extension's Growing Annuals factsheet corroborates a hardy, fall-seeding classification, without adding its own numbers.

Cornell documents two tested approaches: direct fall sowing, with seedlings overwintering in place, or late-winter and early-spring greenhouse sowing, cold-treated, sown late February through mid-March, transplanted in early-to-mid April, flowering by mid-June in Ithaca, New York. Those dates are specific to Cornell's own Ithaca trial, not a portable weeks-before-frost rule for elsewhere, so none of this page's frost-relative fields carry a number for larkspur; every one renders "not available" rather than a figure borrowed from one location's test plot.

The 65°F figure is also why the minimum-soil-temperature field is blank rather than populated: it's a germination ceiling to stay under, the opposite of the minimum-warmth threshold that field is built to hold, so putting it there would read backwards.

Larkspur is grown from seed; there is no started-plug trade to speak of for this crop in our sources.

Frost hardiness

Hardy. Tolerates hard frost. Can go in the ground before the last frost date.

Sourcing notes

Hardy annual with an atypical temperature profile: Cornell University's High Tunnels program states larkspur seeds require LOW temperatures for germination and "do not germinate well above 65F"; a 2-week refrigerated cold-treatment improves germination. Cornell documents two extension-tested approaches: (1) direct fall sowing with seedlings overwintering in place, or (2) late-winter/early-spring greenhouse sowing (late Feb-mid March) after cold treatment, transplanted early-to-mid April, flowering by mid-June in Ithaca, NY. Clemson's Growing Annuals factsheet corroborates a hardy, fall-seeding classification. Because larkspur's sourced temperature figure (65F) is a germination CEILING to avoid, not the schema's usual minimum-warmth threshold, min_soil_temp_f is left blank rather than populated in a way that would read backwards. No source gave a generic weeks-before-first-frost fall-sow figure or a first-bloom day count applicable outside the Ithaca trial, so those fields are left blank.

Related crops

Growing zones for this crop

Nurseries near these locations

Sources