GreenlyBoston: frost dates
United States
In Boston the last spring frost usually comes around 9 April and the first autumn frost around 13 November, which leaves about 218 frost-free days (median of 2016–2025). Tomato seedlings can go into open ground around 19 May.
| Last spring frost | around 9 April |
|---|---|
| First autumn frost | around 13 November |
| Frost-free days | 218 days |
Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.
When to sow and plant
| Crop | Sow for seedlings | Plant out in a greenhouse | Open ground |
|---|---|---|---|
| Achocha | 17 February | 29 March | 19 April |
| Arugula | — | 26 February | sow 19 March |
| Basil | 31 March | 8 May | 29 May |
| Beet | — | 26 February | sow 19 March |
| Bell Pepper | 23 February | 8 May | 29 May |
| Black-eyed Susan | 16 February | — | 19 April |
| Bok Choy | 22 February | 29 March | 19 April |
| Broad bean | — | 26 February | sow 19 March |
| Broccoli | — | 26 February | sow 19 March |
| Brussels Sprouts | 12 January | 26 February | 19 March |
| Cabbage | — | 26 February | sow 19 March |
| Calendula | — | 26 February | sow 19 March |
| Carrot | — | — | sow 19 March |
| Cauliflower | 15 January | 26 February | 19 March |
| Celeriac | 11 January | 29 March | 19 April |
| Celery | 11 January | 29 March | 19 April |
| Celosia | 15 March | 29 April | 20 May |
| Chamomile | — | 26 February | sow 19 March |
| Chayote | 17 January | 15 April | 6 May |
| Chickpea | — | — | sow 19 March |
| Chili Pepper | 7 March | 20 May | 10 June |
| China aster | 17 March | 8 May | 29 May |
| Chives | — | — | sow 19 March |
| Cilantro | — | 26 February | sow 19 March |
| Corn | — | 15 April | sow 6 May |
| Cosmos | 15 March | 29 April | 20 May |
| Cucumber | 27 March | 8 May | 29 May |
| Daikon | — | 26 February | sow 19 March |
| Delphinium | 19 January | — | 19 March |
| Dill | — | 26 February | sow 19 March |
| Eggplant | 27 February | 8 May | 29 May |
| Florence fennel | 12 February | 29 March | 19 April |
| Garden sorrel | — | 26 February | sow 19 March |
| Green Beans | 9 March | 15 April | 6 May |
| Hyssop | — | — | sow 19 March |
| Kale | — | 26 February | sow 19 March |
| Kiwano | 27 March | 28 April | 19 May |
| Kohlrabi | — | 26 February | sow 19 March |
| Leek | 18 December | 26 February | 19 March |
| Lemon balm | — | 26 February | sow 19 March |
| Lettuce | — | 26 February | sow 19 March |
| Lisianthus | 1 December | 26 February | 19 March |
| Lovage | — | — | sow 19 March |
| Luffa | 27 March | 8 May | 29 May |
| Marigold | 15 February | 29 March | 19 April |
| Melon | 17 March | 8 May | 29 May |
| Microgreens | — | 29 April | sow 20 May |
| Moringa | 26 March | 20 May | 10 June |
| Mustard greens | — | 26 February | sow 19 March |
| Napa cabbage | 24 February | 29 March | 19 April |
| Nasturtium | 19 February | 29 March | 19 April |
| Okra | 27 March | 8 May | 29 May |
| Oregano | 28 December | 26 February | 19 March |
| Pansy | 1 January | 26 February | 19 March |
| Parsley | — | 26 February | sow 19 March |
| Parsnip | — | — | sow 19 March |
| Peanut | 1 April | 8 May | 29 May |
| Peas | — | 26 February | sow 19 March |
| Petunia | 6 March | 8 May | 29 May |
| Physalis | 14 March | 28 April | 19 May |
| Pumpkin | 22 March | 28 April | 19 May |
| Purple coneflower | 16 January | — | 19 March |
| Radish | — | — | sow 19 March |
| Sage | 8 January | 26 February | 19 March |
| Snapdragon | 23 December | 26 February | 19 March |
| Spinach | — | 26 February | sow 19 March |
| Stevia | 10 March | 28 April | 19 May |
| Stock | — | 26 February | sow 19 March |
| Sunflower | — | 29 April | sow 20 May |
| Sweet Corn | — | 15 April | sow 6 May |
| Sweet pea | 15 January | 26 February | 19 March |
| Sweet William | — | — | sow 19 March |
| Swiss Chard | — | 26 February | sow 19 March |
| Thyme | — | 26 February | sow 19 March |
| Tomato | 2 March | 28 April | 19 May |
| Turnip | — | 26 February | sow 19 March |
| Watercress | — | 26 February | sow 19 March |
| Watermelon | 6 April | 8 May | 29 May |
| Zinnia | 15 April | 20 May | 10 June |
| Zucchini | 27 March | 28 April | 19 May |
Planting out: a week after the last frost once the soil is warm enough for the crop; frost-hardy crops three weeks before it; an unheated greenhouse three weeks earlier. Seedlings are sown so they are ready on that day.
Boston: weather for the next 7 days
Forecast by Open-Meteo. Nights at or below 0 °C are marked as frost.
Planted in autumn
| Crop | Plant around |
|---|---|
| Bearded Iris | 14 October |
| Crocus | 14 October |
| Daffodil | 14 October |
| Garlic | 14 October |
| Hyacinth | 14 October |
| Lily | 14 October |
| Peony | 14 October |
| Saffron | 14 October |
| Tulip | 14 October |
| Wild garlic | 14 October |
A month before the first autumn frost, so the roots grow before winter.