When to plant · 35 cities · zones 5b–7a
When to plant onions in Massachusetts
Start Spanish Onion seeds indoors around Feb 2 and transplant around Mar 30 — the Massachusetts statewide median, counted from a last spring frost of Apr 27 across 539 ZIP codes and 72 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
Massachusetts onions, by step
Statewide median last frost Apr 27, first fall frost Oct 14, 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) | Feb 2 | Mar 30 | Jul 18 | 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 Massachusetts's ZIP codes resolve to.
Onions in Massachusetts, 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 |
|---|---|---|---|---|
| Bostonzone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Worcesterzone 6a | Apr 23 | Jan 29 | Mar 26 | Jul 14 |
| Springfieldzone 6a | May 3 | Feb 8 | Apr 5 | Jul 24 |
| Cambridgezone 6b | Apr 19 | Jan 25 | Mar 22 | Jul 10 |
| Lowellzone 6b | Apr 30 | Feb 5 | Apr 2 | Jul 21 |
| Brocktonzone 6b | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
| Lynnzone 7a | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| Quincyzone 7a | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| New Bedfordzone 7a | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
| Fall Riverzone 7a | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
| Newtonzone 6b | Apr 19 | Jan 25 | Mar 22 | Jul 10 |
| Lawrencezone 6b | Apr 13 | Jan 19 | Mar 16 | Jul 4 |
| Somervillezone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Framinghamzone 6b | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
| Haverhillzone 6a | May 1 | Feb 6 | Apr 3 | Jul 22 |
| Maldenzone 6b | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Walthamzone 6b | Apr 28 | Feb 3 | Mar 31 | Jul 19 |
| Tauntonzone 6b | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
| Reverezone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Weymouthzone 6b | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| Medfordzone 6b | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Peabodyzone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Chicopeezone 6a | May 3 | Feb 8 | Apr 5 | Jul 24 |
| Methuenzone 6b | Apr 13 | Jan 19 | Mar 16 | Jul 4 |
| Everettzone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Barnstablezone 7a | Apr 16 | Jan 22 | Mar 19 | Jul 7 |
| Attleborozone 6b | Apr 27 | Feb 2 | Mar 30 | Jul 18 |
| Salemzone 7a | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| Leominsterzone 6a | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
| Woburnzone 6b | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| Beverlyzone 6b | May 4 | Feb 9 | Apr 6 | Jul 25 |
| Pittsfieldzone 5b | May 5 | Feb 10 | Apr 7 | Jul 26 |
| Marlboroughzone 6b | May 2 | Feb 7 | Apr 4 | Jul 23 |
| Fitchburgzone 6a | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
| Amherstzone 6a | May 5 | Feb 10 | Apr 7 | Jul 26 |
What these onions become
What Massachusetts 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 Massachusetts: questions
When should I plant onions in Massachusetts?
Transplant around Mar 30 at the statewide median; across the state that date runs from Mar 16 in the warmest tenth of Massachusetts's ZIP codes to Apr 9 in the coldest. To cut the freeze risk to one year in ten, count from May 11 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Massachusetts?
Around Feb 2 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Massachusetts?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 27. In the warmest tenth of Massachusetts's ZIP codes the median last frost falls on or before Apr 13; in the coldest tenth, on or after May 7.
When will Massachusetts onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jul 18: 110 days from transplant.
Which onions grow in Massachusetts?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every Massachusetts city listed here is north of that line.
More for Massachusetts
- 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 → · Massachusetts frost dates → · How frost-date math works →