New Hampshire planting calendar

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

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

Broccoli planting timetable for New Hampshire

Stage	When in New Hampshire	Anchor
Start seeds indoors	early April (April 3)	6 weeks before the last frost (mid-May)
Transplant outside	early May (May 1)	14 days before the last frost (mid-May)
First harvest (estimate)	mid-July (July 20)	~80 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 broccoli 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. Sow early — broccoli bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Start seeds indoors 6–8 weeks before last frost; transplant outdoors 2–4 weeks before last spring frost when soil reaches at least 7 °C (45 °F). Mature plants withstand temperatures as low as −6 °C (21 °F). Heads button (form premature small curds) when exposed to temperatures below 10 °C (50 °F) for extended periods as young seedlings, so harden off carefully. In zones 8–10, a second crop is practical as a fall planting, set out in late summer for harvest before hard freezes.

Frost-risk note

Don't plant before mid-May — a hard freeze can still set young plants back. 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

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: 18–24 inches (45–60 cm) between plants.
Days to harvest: ~80 days from planting out.

Frequently asked questions

When is the best time to plant broccoli in New Hampshire?

In New Hampshire (mostly USDA zone 5b), sow broccoli indoors around early April, transplant outdoors early May (before the last frost, mid-May), and harvest from mid-July. Broccoli 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 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 broccoli in New Hampshire?

Yes. New Hampshire's dominant zone 5b supports broccoli — the key is timing. Broccoli 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 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?

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.