When to plant · 1 city · zone 5b
When to plant onions in Vermont
Start Spanish Onion seeds indoors around Feb 18 and transplant around Apr 15 — the Vermont statewide median, counted from a last spring frost of May 13 across 258 ZIP codes and 50 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
Vermont onions, by step
Statewide median last frost May 13, first fall frost Oct 1, 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 18 | Apr 15 | Aug 3 | 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 Vermont's ZIP codes resolve to.
Onions in Vermont, 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 |
|---|---|---|---|---|
| Burlingtonzone 5b | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
What these onions become
What Vermont 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 Vermont: questions
When should I plant onions in Vermont?
Transplant around Apr 15 at the statewide median; across the state that date runs from Apr 3 in the warmest tenth of Vermont's ZIP codes to Apr 23 in the coldest. To cut the freeze risk to one year in ten, count from May 28 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Vermont?
Around Feb 18 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Vermont?
The ZIP-weighted median of NOAA 1991–2020 station medians is May 13. In the warmest tenth of Vermont's ZIP codes the median last frost falls on or before May 1; in the coldest tenth, on or after May 21.
When will Vermont onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Aug 3: 110 days from transplant.
Which onions grow in Vermont?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every Vermont city listed here is north of that line.
More for Vermont
- 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 → · Vermont frost dates → · How frost-date math works →