New Hampshire planting calendar

When to plant summer squash in New Hampshire — sow, transplant & harvest dates

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

Summer squash planting timetable for New Hampshire

Stage	When in New Hampshire	Anchor
Start seeds indoors	late April (April 24)	3 weeks before the last frost (mid-May)
Transplant outside	late May (May 29)	14 days after the last frost (mid-May)
First harvest (estimate)	late July (July 23)	~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 New Hampshire's climate shifts the summer squash dates

New Hampshire's last spring frost averages mid-May and first fall frost late September, which sets the whole planting clock. New Hampshire is a cold New England state with a brief but reliable summer, milder along the small seacoast and colder in the mountains. Wait for warm soil — summer squash stall in cold ground even after the air warms, so don't rush them out.

Summer squash (zucchini, yellow crookneck, pattypan) wants the same warm soil as cucumbers — 18 °C minimum at sowing depth. A single plant can outproduce a small family once it gets going, so don't over-plant.

Frost-risk note

Don't plant before mid-May — even a light frost will kill seedlings overnight. In the White Mountains and far north (zone 3b) the safe date runs a week or two later.

Regional variation within New Hampshire

the White Mountains and far north (zone 3b) runs roughly 1-2 weeks behind the state average; the short Atlantic seacoast near Portsmouth (zone 6a) can plant 1-2 weeks earlier.

Manchester — USDA zone 5b
Concord — USDA zone 5b
Nashua — USDA zone 5b
Portsmouth — USDA zone 6a

What else to plant in New Hampshire around then

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Quick-grow guide

Sun: Full sun — 6-8 hours direct.
Soil temperature for germination: 21-29 °C (70-85 °F).
Spacing: 24-36 inches (60-90 cm) between plants.
Days to harvest: ~55 days from planting out.

Frequently asked questions

When is the best time to plant summer squash in New Hampshire?

In New Hampshire (mostly USDA zone 5b), sow summer squash indoors around late April, transplant outdoors late May (after the last frost, mid-May), and harvest from late July. Summer squash are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

What USDA zone is New Hampshire?

Most of New Hampshire sits in USDA hardiness zone 5b, with the state spanning roughly 3b-6a from the White Mountains and far north (zone 3b) to the short Atlantic seacoast near Portsmouth (zone 6a). The last spring frost averages mid-May and the first fall frost late September.

Can you grow summer squash in New Hampshire?

Yes. New Hampshire's dominant zone 5b supports summer squash — the key is timing. Summer squash are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

Does the planting date change across New Hampshire?

the White Mountains and far north (zone 3b) runs roughly 1-2 weeks behind the state average; the short Atlantic seacoast near Portsmouth (zone 6a) can plant 1-2 weeks earlier.

What else can I plant in New Hampshire around the same time?

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

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.