Boston, MA Vegetable Planting Calendar
Here are planting dates for 26 vegetables in Boston, for the 2027 season, based on 1991–2020 normals. We start from the 32°F frost odds at Boston Logan International Airport (1.6 mi NNE) and apply CSU Extension timing rules, each listed below with its source.
The timing rules come from Colorado State University Extension (spring) and University of Nebraska–Lincoln Extension (fall count-back), and were written for those states. We apply them to Boston's NOAA frost dates; Massachusetts extension guidance may differ.
Frost anchors: typical last frost Apr 4 (50%), balanced Apr 8 (30%), safe Apr 17 (10%); typical first frost Nov 9. Station Boston Logan International Airport (USW00014739), confidence High. USDA zone 6b–7a (2023). Boston frost dates & growing zone.
What to plant now in Boston
No planting windows from our rules fall in October; see the month-by-month list below.
The list above is for the month this page was built; the box is refreshed in your browser for today's date.
Spring planting dates
“Plant out” means transplanting for crops started indoors and sowing or planting directly in the garden for the others. Each column applies CSU Extension's timing rule to a different last-frost anchor: aggressive = typical date (Apr 4, 50% risk), balanced = Apr 8 (30%), safe = Apr 17 (10%). For hardy crops the cell shows the CSU “as early as” window.
| Crop | How | Start indoors | Plant out: aggressive (50%) | Balanced (30%) | Safe (10%) | Min. soil temp |
|---|---|---|---|---|---|---|
| Tomatoes Very tender (warm season) |
transplant | Apr 4–18 | May 23 | May 23 | May 23 | 50°F |
| Peppers Very tender (warm season) |
transplant | Feb 25 – Mar 11 | Apr 18 | Apr 22 | May 1 | 60°F |
| Potatoes Semi-hardy (cool season) |
plant (seed pieces) | – | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 45°F |
| Onions (dry, from sets) Hardy (cool season) |
plant sets | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 35°F |
| Peas Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Lettuce (leaf) Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 35°F |
| Carrots Semi-hardy (cool season) |
direct sow | – | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 40°F |
| Beans (snap) Tender (warm season) |
direct sow | – | Apr 4 | Apr 8 | Apr 17 | 55°F |
| Summer squash Tender (warm season) |
direct sow | – | Apr 4 | Apr 8 | Apr 17 | 60°F |
| Broccoli Hardy (cool season) |
transplant | Jan 21 – Feb 4 | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Cabbage Hardy (cool season) |
transplant | Jan 21 – Feb 4 | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Cauliflower Semi-hardy (cool season) |
transplant | Feb 4–18 | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 40°F |
| Kohlrabi Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Green onions Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 35°F |
| Radishes Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Spinach Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Turnips Hardy (cool season) |
direct sow | – | Mar 7–21 | Mar 11–25 | Mar 20 – Apr 3 | 40°F |
| Beets Semi-hardy (cool season) |
direct sow | – | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 40°F |
| Swiss chard Semi-hardy (cool season) |
direct sow | – | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 40°F |
| Parsnips Semi-hardy (cool season) |
direct sow | – | Mar 21 – Apr 4 | Mar 25 – Apr 8 | Apr 3–17 | 35°F |
| Sweet corn Tender (warm season) |
direct sow | – | Apr 4 | Apr 8 | Apr 17 | 50°F |
| Cucumbers Tender (warm season) |
direct sow | – | Apr 4 | Apr 8 | Apr 17 | 60°F |
| Eggplant Very tender (warm season) |
transplant | Feb 18 – Mar 11 | Apr 18 | Apr 22 | May 1 | 60°F |
| Cantaloupe Very tender (warm season) |
direct sow | – | Apr 18 | Apr 22 | May 1 | 60°F |
| Watermelon Very tender (warm season) |
direct sow | – | Apr 18 | Apr 22 | May 1 | 60°F |
| Winter squash Very tender (warm season) |
direct sow | – | Apr 18 | Apr 22 | May 1 | 60°F |
A soil thermometer helps here. CSU recommends checking soil temperature at 4 inches (6 inches for beans) before sowing. NOAA doesn't publish soil-temperature normals, so instead of a date, each crop shows CSU's minimum soil temperature.
Fall planting dates
Latest dates for a fall harvest, using the University of Nebraska–Lincoln Extension count-back formula: days to harvest (CSU) + 14-day fall factor + 14-day frost-tender factor for frost-sensitive crops, counted back from the first-frost date. For transplanted crops (CSU days are from transplant) the result is the latest transplant date; seeds go in CSU's transplant-age weeks earlier. We add no harvest period, so these dates give you a first harvest by the first frost, not a long harvest.
| Crop | How | Days counted back | By (typical first frost Nov 9) | By (early first frost Oct 29) |
|---|---|---|---|---|
| Peas | sow | 79 | Aug 22 | Aug 11 |
| Lettuce (leaf) | sow | 74 | Aug 27 | Aug 16 |
| Carrots | sow | 84 | Aug 17 | Aug 6 |
| Beans (snap) | sow | 88 (frost-tender) | Aug 13 | Aug 2 |
| Summer squash | sow | 78 (frost-tender) | Aug 23 | Aug 12 |
| Broccoli | transplant (start seeds Jul 4–18) | 79 | Aug 22 | Aug 11 |
| Cabbage | transplant (start seeds Jun 14–28) | 99 | Aug 2 | Jul 22 |
| Kohlrabi | sow | 64 | Sep 6 | Aug 26 |
| Green onions | sow | 74 | Aug 27 | Aug 16 |
| Radishes | sow | 44 | Sep 26 | Sep 15 |
| Spinach | sow | 54 | Sep 16 | Sep 5 |
| Turnips | sow | 64 | Sep 6 | Aug 26 |
| Beets | sow | 74 | Aug 27 | Aug 16 |
| Swiss chard | sow | 74 | Aug 27 | Aug 16 |
| Cucumbers | sow | 83 (frost-tender) | Aug 18 | Aug 7 |
Month-by-month: what to plant in Boston
What to plant in Boston in January
- Start broccoli seeds indoors (Jan 21 – Feb 4)
- Start cabbage seeds indoors (Jan 21 – Feb 4)
What to plant in Boston in February
- Start cauliflower seeds indoors (Feb 4–18)
- Start eggplant seeds indoors (Feb 18 – Mar 11)
- Start pepper seeds indoors (Feb 25 – Mar 11)
- Start broccoli seeds indoors (Jan 21 – Feb 4)
- Start cabbage seeds indoors (Jan 21 – Feb 4)
What to plant in Boston in March
- Onions (dry, from sets): plant sets outdoors (Mar 7 – Apr 3)
- Peas: direct sow outdoors (Mar 7 – Apr 3)
- Lettuce (leaf): direct sow outdoors (Mar 7 – Apr 3)
- Broccoli: transplant outdoors (Mar 7 – Apr 3)
- Cabbage: transplant outdoors (Mar 7 – Apr 3)
- Kohlrabi: direct sow outdoors (Mar 7 – Apr 3)
- Green onions: direct sow outdoors (Mar 7 – Apr 3)
- Radishes: direct sow outdoors (Mar 7 – Apr 3)
- Spinach: direct sow outdoors (Mar 7 – Apr 3)
- Turnips: direct sow outdoors (Mar 7 – Apr 3)
- Potatoes: plant (seed pieces) outdoors (Mar 21 – Apr 17)
- Carrots: direct sow outdoors (Mar 21 – Apr 17)
- Cauliflower: transplant outdoors (Mar 21 – Apr 17)
- Beets: direct sow outdoors (Mar 21 – Apr 17)
- Swiss chard: direct sow outdoors (Mar 21 – Apr 17)
- Parsnips: direct sow outdoors (Mar 21 – Apr 17)
- Start eggplant seeds indoors (Feb 18 – Mar 11)
- Start pepper seeds indoors (Feb 25 – Mar 11)
What to plant in Boston in April
- Start tomato seeds indoors (Apr 4–18)
- Beans (snap): direct sow outdoors (Apr 4–17)
- Summer squash: direct sow outdoors (Apr 4–17)
- Sweet corn: direct sow outdoors (Apr 4–17)
- Cucumbers: direct sow outdoors (Apr 4–17)
- Peppers: transplant outdoors (Apr 18 – May 1)
- Eggplant: transplant outdoors (Apr 18 – May 1)
- Cantaloupe: direct sow outdoors (Apr 18 – May 1)
- Watermelon: direct sow outdoors (Apr 18 – May 1)
- Winter squash: direct sow outdoors (Apr 18 – May 1)
- Onions (dry, from sets): plant sets outdoors (Mar 7 – Apr 3)
- Peas: direct sow outdoors (Mar 7 – Apr 3)
- Lettuce (leaf): direct sow outdoors (Mar 7 – Apr 3)
- Broccoli: transplant outdoors (Mar 7 – Apr 3)
- Cabbage: transplant outdoors (Mar 7 – Apr 3)
- Kohlrabi: direct sow outdoors (Mar 7 – Apr 3)
- Green onions: direct sow outdoors (Mar 7 – Apr 3)
- Radishes: direct sow outdoors (Mar 7 – Apr 3)
- Spinach: direct sow outdoors (Mar 7 – Apr 3)
- Turnips: direct sow outdoors (Mar 7 – Apr 3)
- Potatoes: plant (seed pieces) outdoors (Mar 21 – Apr 17)
- Carrots: direct sow outdoors (Mar 21 – Apr 17)
- Cauliflower: transplant outdoors (Mar 21 – Apr 17)
- Beets: direct sow outdoors (Mar 21 – Apr 17)
- Swiss chard: direct sow outdoors (Mar 21 – Apr 17)
- Parsnips: direct sow outdoors (Mar 21 – Apr 17)
What to plant in Boston in May
- Tomatoes: transplant outdoors (May 23)
- Peppers: transplant outdoors (Apr 18 – May 1)
- Eggplant: transplant outdoors (Apr 18 – May 1)
- Cantaloupe: direct sow outdoors (Apr 18 – May 1)
- Watermelon: direct sow outdoors (Apr 18 – May 1)
- Winter squash: direct sow outdoors (Apr 18 – May 1)
What to plant in Boston in June
- Start cabbage seeds indoors for a fall crop (Jun 14–28)
What to plant in Boston in July
- Start broccoli seeds indoors for a fall crop (Jul 4–18)
What to plant in Boston in August
- Last day to set out cabbage transplants for a fall harvest (by Aug 2)
- Last day to sow beans (snap) for a fall harvest (by Aug 13)
- Last day to sow carrots for a fall harvest (by Aug 17)
- Last day to sow cucumbers for a fall harvest (by Aug 18)
- Last day to sow peas for a fall harvest (by Aug 22)
- Last day to set out broccoli transplants for a fall harvest (by Aug 22)
- Last day to sow summer squash for a fall harvest (by Aug 23)
- Last day to sow lettuce (leaf) for a fall harvest (by Aug 27)
- Last day to sow green onions for a fall harvest (by Aug 27)
- Last day to sow beets for a fall harvest (by Aug 27)
- Last day to sow swiss chard for a fall harvest (by Aug 27)
What to plant in Boston in September
- Last day to sow kohlrabi for a fall harvest (by Sep 6)
- Last day to sow turnips for a fall harvest (by Sep 6)
- Last day to sow spinach for a fall harvest (by Sep 16)
- Last day to sow radishes for a fall harvest (by Sep 26)
Crop-by-crop notes
When to plant tomatoes in Boston
Very tender crop. CSU Extension's rules are to set tomatoes out at least 2 weeks after the average last frost and only once nights are above 52°F. In Boston, the frost rule alone would allow about Apr 18, but the average nightly low at Boston Logan International Airport isn't above 52°F until May 23, so the night rule sets the date at every risk level: about May 23. Start seeds indoors Apr 4–18, 5–7 weeks before transplanting on May 23. Fruit set suffers when nights drop below 55°F (CSU). The normal low at Boston Logan International Airport reaches 55°F on Jun 2. Set out on May 23, tomato plants would start producing around Jul 27, based on CSU's typical 65 days from transplant to harvest. That leaves 105 days before the typical first frost (Nov 9).
When to plant peppers in Boston
Very tender crop. CSU Extension's rule is 2+ weeks after the average last frost, which puts peppers outside around Apr 18 (typical date), Apr 22 (balanced) or May 1 (safer 10% date). Start seeds indoors Feb 25 – Mar 11, 6–8 weeks ahead of transplanting on Apr 22. Below 55°F at night, fruit set suffers (CSU). At Boston Logan International Airport, the normal low reaches 55°F on Jun 2. Set out on Apr 22, pepper plants would start producing around Jul 1, based on CSU's typical 70 days from transplant to harvest. That leaves 131 days before the typical first frost (Nov 9).
When to plant potatoes in Boston
Semi-hardy crop. CSU says potatoes can be planted as early as 0–2 weeks before the average last frost, in soil of at least 45°F. In Boston, that's roughly Mar 21 – Apr 4 going by the typical date, or Apr 3–17 going by the safer date.
When to plant onions (dry, from sets) in Boston
Hardy crop. Per CSU, onions (dry, from sets) can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 35°F. For Boston, that works out to roughly Mar 7–21 (typical date) or Mar 20 – Apr 3 (safer date).
When to plant peas in Boston
Hardy crop. Per CSU, peas can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Boston, that works out to roughly Mar 7–21 (typical date) or Mar 20 – Apr 3 (safer date). For fall, sow by Aug 22 (Aug 11 to be safe), which is 79 days before the first-frost date.
When to plant lettuce (leaf) in Boston
Hardy crop. CSU says lettuce (leaf) can go in as early as 2–4 weeks before the average last frost: roughly Mar 7–21 in Boston using the typical date, or Mar 20 – Apr 3 using the safer one. Wait until the soil can be worked and is at least 35°F. For fall, sow by Aug 27 (Aug 16 to be safe), which is 74 days before the first-frost date.
When to plant carrots in Boston
Semi-hardy crop. CSU says carrots can be planted as early as 0–2 weeks before the average last frost, in soil of at least 40°F. In Boston, that's roughly Mar 21 – Apr 4 going by the typical date, or Apr 3–17 going by the safer date. For a fall crop, sow by Aug 17, or by Aug 6 to be safe. That's 84 days back from the first-frost date.
When to plant beans (snap) in Boston
Tender crop. CSU says to sow beans (snap) around the average last frost, about Apr 4 in Boston. If you want only a 1-in-10 chance of a later 32°F night, wait until Apr 17. Seeds need soil of at least 55°F. For fall, count back 88 days from the first-frost date. That means sowing by Aug 13, or by Aug 2 to be safe.
When to plant summer squash in Boston
Tender crop. CSU's timing for summer squash is around the average last frost, which is about Apr 4 in Boston. For only a 1-in-10 chance of a later 32°F night, hold off until Apr 17. Seeds want soil at 60°F or warmer. For a fall crop, sow by Aug 23, or by Aug 12 to be safe. That's 78 days back from the first-frost date.
When to plant broccoli in Boston
Hardy crop. Per CSU, broccoli can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Boston, that works out to roughly Mar 7–21 (typical date) or Mar 20 – Apr 3 (safer date). Using CSU's typical 65 days from transplant to harvest, broccoli plants set out on Mar 11 would start producing around May 15. That's 178 days before the typical first frost (Nov 9). For a fall crop, set broccoli transplants out by Aug 22. That's UNL Extension's count-back from the typical first frost (Nov 9), using CSU's 65 days from transplant to harvest. If you grow your own transplants, start seeds Jul 4–18 (CSU: 5–7 weeks to transplant size).
When to plant cabbage in Boston
Hardy crop. Per CSU, cabbage can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Boston, that works out to roughly Mar 7–21 (typical date) or Mar 20 – Apr 3 (safer date). Set out on Mar 11, cabbage plants would start producing around Jun 4, based on CSU's typical 85 days from transplant to harvest. That leaves 158 days before the typical first frost (Nov 9). Fall cabbage: set transplants out by Aug 2. The date counts back from the typical first frost (Nov 9) by UNL Extension's method, using CSU's 85 days from transplant to harvest. Home-grown transplants need seeds started Jun 14–28 (CSU: 5–7 weeks).
When to plant cauliflower in Boston
Semi-hardy crop. Per CSU, cauliflower can go in as early as 0–2 weeks before the average last frost: roughly Mar 21 – Apr 4 in Boston (typical date) or Apr 3–17 (safer date). The soil should be at least 40°F.
When to plant kohlrabi in Boston
Hardy crop. CSU says kohlrabi can go in as early as 2–4 weeks before the average last frost: roughly Mar 7–21 in Boston using the typical date, or Mar 20 – Apr 3 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, count back 64 days from the first-frost date. That means sowing by Sep 6, or by Aug 26 to be safe.
When to plant green onions in Boston
Hardy crop. CSU says green onions can go in as early as 2–4 weeks before the average last frost: roughly Mar 7–21 in Boston using the typical date, or Mar 20 – Apr 3 using the safer one. Wait until the soil can be worked and is at least 35°F. For a fall crop, sow by Aug 27, or by Aug 16 to be safe. That's 74 days back from the first-frost date.
When to plant radishes in Boston
Hardy crop. Per CSU, radishes can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Boston, that works out to roughly Mar 7–21 (typical date) or Mar 20 – Apr 3 (safer date). For fall, count back 44 days from the first-frost date. That means sowing by Sep 26, or by Sep 15 to be safe.
When to plant spinach in Boston
Hardy crop. CSU says spinach can go in as early as 2–4 weeks before the average last frost: roughly Mar 7–21 in Boston using the typical date, or Mar 20 – Apr 3 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, sow by Sep 16 (Sep 5 to be safe), which is 54 days before the first-frost date.
When to plant turnips in Boston
Hardy crop. CSU says turnips can go in as early as 2–4 weeks before the average last frost: roughly Mar 7–21 in Boston using the typical date, or Mar 20 – Apr 3 using the safer one. Wait until the soil can be worked and is at least 40°F. For a fall crop, sow by Sep 6, or by Aug 26 to be safe. That's 64 days back from the first-frost date.
When to plant beets in Boston
Semi-hardy crop. Per CSU, beets can go in as early as 0–2 weeks before the average last frost: roughly Mar 21 – Apr 4 in Boston (typical date) or Apr 3–17 (safer date). The soil should be at least 40°F. For fall, sow by Aug 27 (Aug 16 to be safe), which is 74 days before the first-frost date.
When to plant swiss chard in Boston
Semi-hardy crop. Per CSU, swiss chard can go in as early as 0–2 weeks before the average last frost: roughly Mar 21 – Apr 4 in Boston (typical date) or Apr 3–17 (safer date). The soil should be at least 40°F. For a fall crop, sow by Aug 27, or by Aug 16 to be safe. That's 74 days back from the first-frost date.
When to plant parsnips in Boston
Semi-hardy crop. CSU says parsnips can be planted as early as 0–2 weeks before the average last frost, in soil of at least 35°F. In Boston, that's roughly Mar 21 – Apr 4 going by the typical date, or Apr 3–17 going by the safer date.
When to plant sweet corn in Boston
Tender crop. CSU says to sow sweet corn around the average last frost, about Apr 4 in Boston. If you want only a 1-in-10 chance of a later 32°F night, wait until Apr 17. Seeds need soil of at least 50°F.
When to plant cucumbers in Boston
Tender crop. Sow cucumbers around the average last frost, per CSU: about Apr 4 in Boston. Waiting until Apr 17 cuts the chance of a later 32°F night to 1 in 10. Seeds need soil of at least 60°F. For a fall crop, sow by Aug 18, or by Aug 7 to be safe. That's 83 days back from the first-frost date.
When to plant eggplant in Boston
Very tender crop. Following CSU Extension's rule (2+ weeks after the average last frost), set eggplant out around Apr 18 with the typical date, Apr 22 for a balanced choice, or May 1 with the safer 10% date. Sow seeds indoors Feb 18 – Mar 11, 6–9 weeks before transplanting on Apr 22. Using CSU's typical 60 days from transplant to harvest, eggplant plants set out on Apr 22 would start producing around Jun 21. That's 141 days before the typical first frost (Nov 9).
When to plant cantaloupe in Boston
Very tender crop. CSU Extension says to plant cantaloupe 2+ weeks after the average last frost: about Apr 18 (typical date), Apr 22 (balanced) or May 1 (safer 10% date). Wait for soil of at least 60°F.
When to plant watermelon in Boston
Very tender crop. CSU Extension says to plant watermelon 2+ weeks after the average last frost: about Apr 18 (typical date), Apr 22 (balanced) or May 1 (safer 10% date). Wait for soil of at least 60°F.
When to plant winter squash in Boston
Very tender crop. CSU Extension's rule is to plant winter squash at least 2 weeks after the average last frost. That's about Apr 18 using the typical date, Apr 22 as a balanced choice, or May 1 if you go by the safer 10% date. Seeds need soil of at least 60°F.
How these dates are calculated
| Rule | Applies to | Source (scope) |
|---|---|---|
| Hardy (cool season): “As early as 2-4 weeks before the date of the average last spring frost.” | Onions (dry, from sets), Peas, Lettuce (leaf), Broccoli, Cabbage, Kohlrabi, Green onions, Radishes, Spinach, Turnips | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Semi-hardy (cool season): “As early as 0-2 weeks before the date of the average last spring frost.” | Potatoes, Carrots, Cauliflower, Beets, Swiss chard, Parsnips | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Tender (warm season): “From seed: around the date of the average last spring frost” | Beans (snap), Summer squash, Sweet corn, Cucumbers | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Very tender (warm season): “Typically 2+ weeks after the average last spring frost date.” | Tomatoes, Peppers, Eggplant, Cantaloupe, Watermelon, Winter squash | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Start indoors = transplant age (weeks) before the balanced transplant date; days to harvest; minimum soil temperature | Crops with those values in CSU's table | CSU Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Night-temperature dates: first day the NOAA 1991–2020 daily normal low (DLY-TMIN-NORMAL) is above the CSU transplant threshold or reaches the fruit-set threshold | Tomatoes (above 52°F at transplant, 55°F fruit set), peppers (55°F fruit set) | CSU Growing Tomatoes, CSU Peppers and Eggplants (written for Colorado; generic temperature thresholds applied nationwide with attribution) |
| Fall count-back: days to harvest + fall factor (14) + frost-tender factor (14) | Peas, Lettuce (leaf), Carrots, Beans (snap), Summer squash, Broccoli, Cabbage, Kohlrabi, Green onions, Radishes, Spinach, Turnips, Beets, Swiss chard, Cucumbers | UNL Extension, Fall Vegetable Gardening (G1343) (written for Nebraska; the count-back formula is applied nationwide with attribution) |
CSU states its spring rules relative to “the average last spring frost.” We use the 50% date as that average and also show the 30% and 10% anchors. See the methodology for details and limitations.
FAQ
When should I start seeds indoors in Boston?
Sow tomatoes indoors Apr 4–18 and peppers Feb 25 – Mar 11. We work back from a balanced (30%-risk) transplant date using CSU's transplant ages.
When should I plant tomatoes outside in Boston?
About May 23 at every risk level, because the night rule decides it. CSU wants nights above 52°F at transplant, and the average nightly low at Boston Logan International Airport first rises above 52°F on May 23. CSU's frost rule (2+ weeks after the average last frost) would allow about Apr 18 here.
What can I plant in Boston in the fall?
Based on UNL Extension's count-back from the typical first frost (Nov 9), the deadlines are: peas by Aug 22; lettuce (leaf) by Aug 27; carrots by Aug 17; beans (snap) by Aug 13; summer squash by Aug 23; broccoli by Aug 22 (transplants); cabbage by Aug 2 (transplants); kohlrabi by Sep 6; green onions by Aug 27; radishes by Sep 26; spinach by Sep 16; turnips by Sep 6; beets by Aug 27; swiss chard by Aug 27; cucumbers by Aug 18.