USDA Hardiness Zone 6a
Frost Dates for 01451 — Harvard, Massachusetts
Averages from Fitchburg Muni Ap, Ma US, the nearest reporting station, 9.1 miles away.
Plant tender crops after April 29, and expect the first autumn freeze around October 11. That leaves about 164 frost-free days.
- Last spring frost
- April 29
- First fall frost
- October 11
- Growing season
- 164 days
- Hardiness zone
- 6a
50% probability
50% probability
frost-free
-10 to -5°F annual low
Planting calendar for 01451
| When | What to do |
|---|---|
| February 18 – March 4 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| March 4 – March 18 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| April 1 – April 15 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| April 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 19 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 27 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 11 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after April 29 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Harvard, Massachusetts are past their last freeze. Harvest before October 11, which leaves roughly 164 frost-free days.
ZIP 01451 sits in USDA hardiness zone 6a, meaning the average coldest night of the year falls between -10 to -5°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.