When to plant · 9 cities · zones 7a–8a
When to plant onions in Arkansas
Start Spanish Onion seeds indoors around Jan 3 and transplant around Feb 28 — the Arkansas statewide median, counted from a last spring frost of Mar 28 across 615 ZIP codes and 117 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
5 of these Arkansas cities sit below 36° N, where a long-day onion never gets the day length to bulb. They are flagged in the table; plant a short-day type there.
Arkansas onions, by step
Statewide median last frost Mar 28, first fall frost Nov 5, 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 3 | Feb 28 | Jun 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 Arkansas's ZIP codes resolve to.
Onions in Arkansas, 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 |
|---|---|---|---|---|
| Little Rockzone 8abelow 36° N · short-day onion | Mar 21 | Dec 27 | Feb 21 | Jun 11 |
| Fayettevillezone 7a | Apr 15 | Jan 21 | Mar 18 | Jul 6 |
| Fort Smithzone 8abelow 36° N · short-day onion | Mar 25 | Dec 31 | Feb 25 | Jun 15 |
| Springdalezone 7a | Apr 4 | Jan 10 | Mar 7 | Jun 25 |
| Jonesborozone 7bbelow 36° N · short-day onion | Apr 1 | Jan 7 | Mar 4 | Jun 22 |
| Rogerszone 7a | Apr 12 | Jan 18 | Mar 15 | Jul 3 |
| Conwayzone 8abelow 36° N · short-day onion | Apr 2 | Jan 8 | Mar 5 | Jun 23 |
| North Little Rockzone 8abelow 36° N · short-day onion | Mar 16 | Dec 22 | Feb 16 | Jun 6 |
| Bentonvillezone 7a | Apr 12 | Jan 18 | Mar 15 | Jul 3 |
What these onions become
What Arkansas 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 Arkansas: questions
When should I plant onions in Arkansas?
Transplant around Feb 28 at the statewide median; across the state that date runs from Feb 16 in the warmest tenth of Arkansas's ZIP codes to Mar 12 in the coldest. To cut the freeze risk to one year in ten, count from Apr 13 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Arkansas?
Around Jan 3 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Arkansas?
The ZIP-weighted median of NOAA 1991–2020 station medians is Mar 28. In the warmest tenth of Arkansas's ZIP codes the median last frost falls on or before Mar 16; in the coldest tenth, on or after Apr 9.
When will Arkansas onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jun 18: 110 days from transplant.
Which onions grow in Arkansas?
Spanish Onion is a long-day onion: it bulbs at 14–16 hours of daylight, which it gets above roughly 36° N. 5 of the 9 Arkansas cities listed here sit below that line; grow a short-day onion there.
More for Arkansas
- 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 → · Arkansas frost dates → · How frost-date math works →