Kentucky planting calendar

When to plant onions in Kentucky — sow, transplant & harvest dates

Kentucky is mostly USDA zone 6b (range 6a-7b). Dates below are derived from onions's frost tolerance and Kentucky's frost window — not generic national averages.

Onions planting timetable for Kentucky

Stage	When in Kentucky	Anchor
Start seeds indoors	early February (February 4)	10 weeks before the last frost (mid-April)
Transplant outside	mid-March (March 18)	28 days before the last frost (mid-April)
First harvest (estimate)	early July (July 6)	~110 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Kentucky's climate shifts the onions dates

Kentucky's last spring frost averages mid-April and first fall frost mid-October, which sets the whole planting clock. Kentucky has a mild four-season climate with a long, humid summer and a winter that rarely tests hardy perennials. Sow early — onions bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Onions are day-length sensitive: long-day varieties (zones 1–6) begin bulbing when days exceed 14 hours, short-day types (zones 7–10) bulb at 10–12 hours, and intermediate-day varieties span zones 5–6. Start seeds indoors 10–12 weeks before the last spring frost and transplant out 4–6 weeks before it — young onion seedlings tolerate frost down to about -6 °C once hardened off. In zones 8–10 a second planting from sets in autumn is common, overwintering for an early-summer harvest.

Frost-risk note

Don't plant before mid-April — a hard freeze can still set young plants back. In the eastern Appalachian highlands (zone 6a) the safe date runs a week or two later.

Regional variation within Kentucky

the eastern Appalachian highlands (zone 6a) runs roughly 1-2 weeks behind the state average; the Ohio River valley around Louisville (zone 7b) can plant 1-2 weeks earlier.

Louisville — USDA zone 7a
Lexington — USDA zone 6b
Bowling Green — USDA zone 7a
Covington — USDA zone 6b

What else to plant in Kentucky around then

The same early window suits peas, lettuce, spinach, and onion sets.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 10-35 °C (50-95 °F).
Spacing: 4-6 inches (10-15 cm) between plants.
Days to harvest: ~110 days from planting out.

Frequently asked questions

When is the best time to plant onions in Kentucky?

In Kentucky (mostly USDA zone 6b), sow onions indoors around early February, transplant outdoors mid-March (before the last frost, mid-April), and harvest from early July. Onions are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

What USDA zone is Kentucky?

Most of Kentucky sits in USDA hardiness zone 6b, with the state spanning roughly 6a-7b from the eastern Appalachian highlands (zone 6a) to the Ohio River valley around Louisville (zone 7b). The last spring frost averages mid-April and the first fall frost mid-October.

Can you grow onions in Kentucky?

Yes. Kentucky's dominant zone 6b supports onions — the key is timing. Onions are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

Does the planting date change across Kentucky?

the eastern Appalachian highlands (zone 6a) runs roughly 1-2 weeks behind the state average; the Ohio River valley around Louisville (zone 7b) can plant 1-2 weeks earlier.

What else can I plant in Kentucky around the same time?

The same early window suits peas, lettuce, spinach, and onion sets.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.