Mercerville-Hamilton Square, NJ planting zone & frost dates
Mercerville-Hamilton Square is in USDA hardiness zone 7a. The last spring frost usually comes around April 25 and the first fall frost around October 16, for a growing season of about 173 days.
Planting calendar for Mercerville-Hamilton Square
Dates are counted from the average last spring frost (April 25) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: May 2 – May 9 |
| Peppers | Start seeds indoors: Feb 14 – Feb 28 Transplant outdoors: May 9 – May 16 |
| Eggplant | Start seeds indoors: Feb 14 – Feb 28 Transplant outdoors: May 9 – May 16 |
| Broccoli | Start seeds indoors: Feb 14 – Feb 28 Transplant outdoors: Mar 28 – Apr 11 |
| Cabbage | Start seeds indoors: Feb 14 – Feb 28 Transplant outdoors: Mar 28 – Apr 11 |
| Onions (sets) | Plant outdoors: Mar 28 – Apr 11 |
| Peas | Sow outdoors: Mar 14 – Mar 28 |
| Spinach | Sow outdoors: Mar 14 – Mar 28 |
| Lettuce | Sow outdoors: Mar 28 – Apr 11 |
| Carrots | Sow outdoors: Mar 28 – Apr 11 |
| Potatoes | Plant outdoors: Mar 28 – Apr 11 |
| Beans | Sow outdoors: May 2 – May 9 |
| Sweet corn | Sow outdoors: May 2 – May 9 |
| Cucumbers | Sow outdoors: May 2 – May 9 |
| Squash & zucchini | Sow outdoors: May 2 – May 9 |
| Basil | Start seeds indoors: Mar 14 – Mar 28 Transplant outdoors: May 2 – May 9 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 21 (8 weeks before the average first fall frost on Oct 16).
Useful for zone 7a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 12 | Apr 25 | May 12 |
| First 32°F frost in fall is before | Oct 29 | Oct 16 | Oct 4 |
How to read it: in spring there is a 10% chance of a frost after May 12, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 4. A hard freeze (28°F) usually ends around April 10.
Nearby cities
- Mercerville zone 7a, last frost Apr 17
- Hamilton Square zone 7a, last frost Apr 25
- Trenton zone 7a, last frost Apr 17
- Princeton zone 7a, last frost Apr 25
- Ewing zone 7b, last frost Apr 17
- Princeton Meadows zone 7a, last frost Apr 25
- Franklin Park zone 7a, last frost Apr 15
- Mount Holly zone 7b, last frost Apr 15
Questions
What growing zone is Mercerville-Hamilton Square, NJ?
Mercerville-Hamilton Square is in USDA Plant Hardiness Zone 7a (average extreme winter low 0°F to 5°F), according to the USDA 2023 map.
When is the last frost in Mercerville-Hamilton Square?
The average last spring frost (32°F) in Mercerville-Hamilton Square is April 25. There is still a 10% chance of frost until May 12.
When can I plant tomatoes in Mercerville-Hamilton Square?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 2 – May 9. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Hightstown 2 W, NJ (USC00283951), 10.0 km (6.2 mi) from the city center, elevation 30 m, based on 27 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.