New Hampshire · zones 4b–6a
When to plant basil in New Hampshire.
Sow or transplant between Jun 5 to Aug 5 in a typical year, keyed to New Hampshire's median last frost around May 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Basil dates for a typical New Hampshire season.
1 · Start indoors
Apr 24 to Jun 24
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jun 5 to Aug 5
Keyed to the ~May 15 last frost. Sow 0.25" deep, 8" apart.
Harvest
~40 days later
~0.5 lb per plant over ~12 weeks.
New Hampshire spans more than one climate: Zone 5 is the most common zone, but the state runs 4b to 6a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In New Hampshire: watch for
The pests that find basil here.
The short season here, about 136 frost-free days, keeps basil in front of aphids only briefly. One early row cover usually carries a planting through the worst of it.
Fine webbing and pale stippling in hot, dry spells.
Organic fix: Spray the undersides with water, then insecticidal soap or neem.
Yellowing with gray fuzz underneath, or white powder on top.
Organic fix: Space for airflow, water at the base, spray neem.
Metallic beetles chewing basil and mint leaves to lace.
Organic fix: Handpick into soapy water in the morning; neem.
Your season math: New Hampshire gives basil about 136 frost-free days, and it needs roughly 40 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting basil in New Hampshire: questions
When should I plant basil in New Hampshire?+
In a typical New Hampshire year, sow basil or set out transplants between Jun 5 to Aug 5, keyed to the state's median last frost around May 15. Your exact dates shift with your ZIP code and microclimate.
When do I start basil seeds indoors in New Hampshire?+
Start seeds inside about 6 weeks before set-out: roughly Apr 24 to Jun 24 for a typical New Hampshire season.
What USDA zone is New Hampshire?+
New Hampshire spans zones 4b–6a, mostly zone 5. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many basil plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.