When to plant · 20 cities · zones 7a–7b
When to plant onions in New Jersey
Start Spanish Onion seeds indoors around Jan 21 and transplant around Mar 18 — the New Jersey statewide median, counted from a last spring frost of Apr 15 across 604 ZIP codes and 58 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
New Jersey onions, by step
Statewide median last frost Apr 15, first fall frost Oct 28, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.
| Cultivar | Start indoors | Plant out | First harvest | Days |
|---|---|---|---|---|
| Spanish OnionYellow Sweet Spanish (long-day) | Jan 21 | Mar 18 | Jul 6 | 110 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station New Jersey's ZIP codes resolve to.
Onions in New Jersey, city by city
Spanish Onion, scheduled from each city's nearest NOAA station — the same dates as its frost page.
| City | Last frost | Start indoors | Plant out | First harvest |
|---|---|---|---|---|
| Newarkzone 7b | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Jersey Cityzone 7b | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Patersonzone 7a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Elizabethzone 7b | Apr 2 | Jan 8 | Mar 5 | Jun 23 |
| Trentonzone 7a | Apr 17 | Jan 23 | Mar 20 | Jul 8 |
| Cliftonzone 7a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Bayonnezone 7b | Apr 2 | Jan 8 | Mar 5 | Jun 23 |
| East Orangezone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Camdenzone 7b | Mar 30 | Jan 5 | Mar 2 | Jun 20 |
| Passaiczone 7b | Apr 3 | Jan 9 | Mar 6 | Jun 24 |
| Union Cityzone 7b | Mar 30 | Jan 5 | Mar 2 | Jun 20 |
| Vinelandzone 7a | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Hobokenzone 7b | Mar 30 | Jan 5 | Mar 2 | Jun 20 |
| New Brunswickzone 7a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Perth Amboyzone 7b | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Plainfieldzone 7a | Apr 11 | Jan 17 | Mar 14 | Jul 2 |
| West New Yorkzone 7b | Mar 30 | Jan 5 | Mar 2 | Jun 20 |
| Sayrevillezone 7a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Hackensackzone 7b | Apr 3 | Jan 9 | Mar 6 | Jun 24 |
| Lindenzone 7b | Apr 11 | Jan 17 | Mar 14 | Jul 2 |
What these onions become
What New Jersey onions need
Yellow Sweet Spanish Onion Seed
A long-day storage onion with enough sugar to sweat down without scorching. The aromatic base under every tomato sauce on this site.
Organic Seed Starter Potting MixMust have
Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.
72-Cell Trays with 1020 Bottoms, 5-PackMust have
The cheap black nursery trays crack after one season and flex enough to break roots when you lift them. These do not. Over five seasons the price per use is lower than the throwaways.
T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have
A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.
Rapitest Soil Test Kit
In-ground growers are guessing until they test. pH outside 6.0–6.8 locks nutrients out no matter how much fertiliser you add, and no amount of feeding fixes that.
Pure Organic Worm Castings, 15 lb
Not a fertiliser so much as a soil-biology inoculant with a mild nutrient charge. A cup in each planting hole is a cheap, unglamorous improvement you can measure by August.
Garden Harvest Basket with Tool Caddy
A harvest basket that doubles as a colander means the hose rinse happens in the garden, and the dirt stays outside. On a 20-pound tomato day that is a genuine time saving.
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Onions in New Jersey: questions
When should I plant onions in New Jersey?
Transplant around Mar 18 at the statewide median; across the state that date runs from Mar 5 in the warmest tenth of New Jersey's ZIP codes to Mar 28 in the coldest. To cut the freeze risk to one year in ten, count from May 1 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in New Jersey?
Around Jan 21 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in New Jersey?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 15. In the warmest tenth of New Jersey's ZIP codes the median last frost falls on or before Apr 2; in the coldest tenth, on or after Apr 25.
When will New Jersey onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jul 6: 110 days from transplant.
Which onions grow in New Jersey?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every New Jersey city listed here is north of that line.
More for New Jersey
- When to plant tomatoes
- When to plant peppers
- When to plant tomatillos
- When to plant basil
- When to plant cilantro
- When to plant carrots
- When to plant mustard greens
Onions in every state → · New Jersey frost dates → · How frost-date math works →