Maine planting calendar

When to plant kohlrabi in Maine — sow, transplant & harvest dates

Maine is mostly USDA zone 5a (range 3b-6a). Dates below are derived from kohlrabi's frost tolerance and Maine's frost window — not generic national averages.

Kohlrabi planting timetable for Maine

Stage	When in Maine	Anchor
Start seeds indoors	early April (April 10)	5 weeks before the last frost (mid-May)
Transplant outside	late April (April 24)	21 days before the last frost (mid-May)
First harvest (estimate)	mid-June (June 18)	~55 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 Maine's climate shifts the kohlrabi dates

Maine's last spring frost averages mid-May and first fall frost late September, which sets the whole planting clock. Maine is a short-season cold-climate state, milder along the coast and noticeably colder in the northern and mountain interior. Sow early — kohlrabi bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Kohlrabi is a fast-maturing brassica that tolerates light frost down to about -4 °C but turns woody and pithy when daytime temperatures exceed 27 °C; transplant or direct-sow 3–4 weeks before the last spring frost for a summer harvest, or time a second sowing so plants mature in the cool days of early autumn. Harvest promptly when the swollen stem reaches 5–7 cm (2–3 inches) in diameter — larger bulbs become fibrous. Succession-sow every 3 weeks to extend the harvest window.

Frost-risk note

Don't plant before mid-May — a hard freeze can still set young plants back. In the far north Aroostook County interior (zone 3b) the safe date runs a week or two later.

Regional variation within Maine

the far north Aroostook County interior (zone 3b) runs roughly 1-2 weeks behind the state average; the southern coast around Portland (zone 6a) can plant 1-2 weeks earlier.

Portland — USDA zone 6a
Bangor — USDA zone 5a
Augusta — USDA zone 5b
Presque Isle — USDA zone 4a

What else to plant in Maine 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: 7-29 °C (45-85 °F).
Spacing: 6-9 inches (15-23 cm) between plants.
Days to harvest: ~55 days from planting out.

Frequently asked questions

When is the best time to plant kohlrabi in Maine?

In Maine (mostly USDA zone 5a), sow kohlrabi indoors around early April, transplant outdoors late April (before the last frost, mid-May), and harvest from mid-June. Kohlrabi are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

What USDA zone is Maine?

Most of Maine sits in USDA hardiness zone 5a, with the state spanning roughly 3b-6a from the far north Aroostook County interior (zone 3b) to the southern coast around Portland (zone 6a). The last spring frost averages mid-May and the first fall frost late September.

Can you grow kohlrabi in Maine?

Yes. Maine's dominant zone 5a supports kohlrabi — the key is timing. Kohlrabi are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

Does the planting date change across Maine?

the far north Aroostook County interior (zone 3b) runs roughly 1-2 weeks behind the state average; the southern coast around Portland (zone 6a) can plant 1-2 weeks earlier.

What else can I plant in Maine 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.