New Hampshire · zones 4b–6a
When to plant sweet potatoes in New Hampshire.
Sow or transplant between Jun 21 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.
Season checkSweet Potato needs about 110 days and your first frost comes too early for that. Even the earliest date shown will not ripen outdoors here, grow it in a container you can move, or treat it as a short-season variety.
The 2026 windows
Sweet Potatoes dates for a typical New Hampshire season.
1 · Start indoors
May 10 to Jun 24
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jun 21 to Aug 5
Keyed to the ~May 15 last frost. Sow 3" deep, 14" apart.
Harvest
~110 days later
~2.5 lb per plant over ~1 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 sweet potatoes here.
The short season here, about 136 frost-free days, keeps sweet potato in front of wireworms & white grubs only briefly. One early row cover usually carries a planting through the worst of it.
Wireworms & white grubs
Shallow holes and grooves chewed into the roots, found only at digging time.
Organic fix: Avoid planting into ground that was in sod last year; rotate away from grassy beds.
Clusters on the tender growing tips of new vines.
Organic fix: Hose them off in the morning, or use insecticidal soap.
Black rot
Dry, firm dark patches on the roots, usually found at harvest or in storage, with a sweet fruity smell.
Organic fix: Start from clean slips cut well above the soil line, never save roots from a bad crop, and rotate 3 years.
Your season math: New Hampshire gives sweet potatoes about 136 frost-free days, and it needs roughly 110 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting sweet potatoes in New Hampshire: questions
When should I plant sweet potatoes in New Hampshire?+
In a typical New Hampshire year, sow sweet potatoes or set out transplants between Jun 21 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 sweet potatoes seeds indoors in New Hampshire?+
Start seeds inside about 6 weeks before set-out: roughly May 10 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 sweet potatoes 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.