When to plant · 23 cities · zones 6a–7a
When to plant onions in Indiana
Start Spanish Onion seeds indoors around Jan 28 and transplant around Mar 25 — the Indiana statewide median, counted from a last spring frost of Apr 22 across 807 ZIP codes and 124 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
Indiana onions, by step
Statewide median last frost Apr 22, first fall frost Oct 20, 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 28 | Mar 25 | Jul 13 | 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 Indiana's ZIP codes resolve to.
Onions in Indiana, 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 |
|---|---|---|---|---|
| Indianapoliszone 6b | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Fort Waynezone 6a | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Evansvillezone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Fisherszone 6a | Apr 21 | Jan 27 | Mar 24 | Jul 12 |
| South Bendzone 6a | May 1 | Feb 6 | Apr 3 | Jul 22 |
| Carmelzone 6a | Apr 21 | Jan 27 | Mar 24 | Jul 12 |
| Bloomingtonzone 6b | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Hammondzone 6a | Apr 23 | Jan 29 | Mar 26 | Jul 14 |
| Noblesvillezone 6a | Apr 21 | Jan 27 | Mar 24 | Jul 12 |
| Lafayettezone 6a | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
| Greenwoodzone 6a | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Garyzone 6a | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
| Munciezone 6a | Apr 16 | Jan 22 | Mar 19 | Jul 7 |
| Westfieldzone 6a | Apr 21 | Jan 27 | Mar 24 | Jul 12 |
| Kokomozone 6a | Apr 27 | Feb 2 | Mar 30 | Jul 18 |
| Terre Hautezone 6a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Andersonzone 6a | Apr 19 | Jan 25 | Mar 22 | Jul 10 |
| Elkhartzone 6a | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
| Jeffersonvillezone 7a | Mar 31 | Jan 6 | Mar 3 | Jun 21 |
| Columbuszone 6b | Apr 11 | Jan 17 | Mar 14 | Jul 2 |
| Mishawakazone 6a | May 1 | Feb 6 | Apr 3 | Jul 22 |
| Lawrencezone 6a | Apr 18 | Jan 24 | Mar 21 | Jul 9 |
| West Lafayettezone 6a | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
What these onions become
What Indiana 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 Indiana: questions
When should I plant onions in Indiana?
Transplant around Mar 25 at the statewide median; across the state that date runs from Mar 14 in the warmest tenth of Indiana's ZIP codes to Mar 31 in the coldest. To cut the freeze risk to one year in ten, count from May 7 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Indiana?
Around Jan 28 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Indiana?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 22. In the warmest tenth of Indiana's ZIP codes the median last frost falls on or before Apr 11; in the coldest tenth, on or after Apr 28.
When will Indiana onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jul 13: 110 days from transplant.
Which onions grow in Indiana?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every Indiana city listed here is north of that line.
More for Indiana
- 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 → · Indiana frost dates → · How frost-date math works →