When to Plant Cucumbers in New Hampshire
Published: April 21, 2026
New Hampshire gardeners in Zone 5b have a 28-week frost-free window for cucumber (April 7 to October 22). Warm-season crops like cucumber must be started indoors early to maximize the short window — New Hampshire's late spring and early fall frost dates leave little room for error. This guide gives exact dates for New Hampshire based on your local frost calendar.
Cucumber Planting Dates for New Hampshire
| Start seeds indoors | March 17–24 |
| Last frost (average) | April 7 |
| Transplant outdoors | April 14–24 |
| Direct sow outdoors | April 14–24 |
| Expect first harvest | June 3 – June 23 |
| Fall crop start | August 13–23 |
| Fall harvest | October 2 |
| First fall frost (average) | October 22 |
Dates above assume Zone 5b, the most common zone in New Hampshire. Gardeners in cooler Nashua (Zone 5b) plant 1–2 weeks later; warmer Portsmouth (Zone 5a) can plant 1–2 weeks earlier.
Growing Cucumbers in New Hampshire's Climate
New Hampshire's cold Zone 5b climate puts warm-season cucumber at the edge of viability — but the edge is workable with good planning. Starting seeds indoors under lights in late winter is the most important step; skipping this puts the whole harvest at risk from the short outdoor growing window.
Season extenders pay for themselves many times over in New Hampshire. Row covers placed over transplants in early spring add 5°F to 8°F of protection and can extend the season two to three weeks on each end. Black plastic mulch warms the soil to the temperatures cucumber needs for aggressive root growth.
Common cucumber pests to watch for in New Hampshire include Cucumber Beetle and Squash Vine Borer. The first line of defense is companion planting: Radish and Nasturtium planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Cucumber Garden Calendar for New Hampshire
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| April | Transplant outdoors | Soil temp must be 60°F+; nighttime lows above 50°F |
| May ← | — | Dormant season |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Start fall crop seeds | Fall transplants go in 10 weeks before first frost |
| August | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining cucumber; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Cucumber Growing Tips for New Hampshire Gardeners
- •Direct sow after last frost rather than transplanting — cucumbers establish faster from seed in warm soil.
- •Trellis vertically to save space and reduce powdery mildew from soil splash.
- •New Hampshire's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Harvest every 2–3 days — cucumbers left on the vine signal the plant to stop producing new fruit.
Companion Planting for Cucumbers in New Hampshire
In New Hampshire's cold climate, planting cucumber with Radish and Nasturtium helps deter pests and improve soil. Avoid planting near Aromatic Herbs and Potato, which inhibit cucumber growth through root chemistry or shared pest pressure. See the full cucumber companion planting guide for the complete list.
Cucumbers Planting Dates by City in New Hampshire
Top cities in New Hampshire — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant cucumber in New Hampshire?
In New Hampshire (Zone 5b), start cucumber seeds indoors around March 17–24 and transplant outdoors around April 14–24 — 1 weeks after the state's average last frost of April 7.
What is the last frost date in New Hampshire?
New Hampshire's average last frost date is April 7 in the state's most common Zone 5b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow cucumber year-round in New Hampshire?
Not year-round — New Hampshire's cold season stops cucumber production. The cucumber season runs April 7 to October 22, roughly 28 weeks. A fall crop extends harvest into late autumn.
What cucumber varieties grow best in New Hampshire?
For New Hampshire's Zone 5b, Marketmore 76 and Straight Eight tolerate cooler nights and are the most reliable choices.
When do I start cucumber seeds indoors in New Hampshire?
Start cucumber seeds indoors in New Hampshire around March 17–24, which is 3 weeks before the state's average last frost of April 7. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.