When to plant · 38 cities · zones 5b–6a
When to plant tomatoes in Illinois
Start Roma Tomato seeds indoors around Mar 6 and transplant around Apr 24 — the Illinois statewide median, counted from a last spring frost of Apr 17 across 1,402 ZIP codes and 192 NOAA stations.
The rule: Six weeks indoors at 75–85 °F soil, then transplant a week after the last frost and cage at transplant.
Illinois tomatoes, by cultivar
Statewide median last frost Apr 17, first fall frost Oct 21, 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 |
|---|---|---|---|---|
| Roma TomatoRoma VF (determinate paste) | Mar 6 | Apr 24 | Jul 8 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 6 | Apr 24 | Jul 13 | 80 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 Illinois's ZIP codes resolve to.
Tomatoes in Illinois, city by city
Roma Tomato, scheduled from each city's nearest NOAA station — the same dates as its frost page.
| City | Last frost | Start indoors | Plant out | First harvest |
|---|---|---|---|---|
| Chicagozone 6a | Apr 10 | Feb 27 | Apr 17 | Jul 1 |
| Aurorazone 5b | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Napervillezone 5b | Apr 28 | Mar 17 | May 5 | Jul 19 |
| Jolietzone 5b | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Rockfordzone 5b | Apr 24 | Mar 13 | May 1 | Jul 15 |
| Elginzone 5b | Apr 26 | Mar 15 | May 3 | Jul 17 |
| Springfieldzone 6a | Apr 15 | Mar 4 | Apr 22 | Jul 6 |
| Peoriazone 6a | Apr 16 | Mar 5 | Apr 23 | Jul 7 |
| Champaignzone 6a | Apr 15 | Mar 4 | Apr 22 | Jul 6 |
| Waukeganzone 6a | Apr 30 | Mar 19 | May 7 | Jul 21 |
| Cicerozone 6a | Apr 11 | Feb 28 | Apr 18 | Jul 2 |
| Bloomingtonzone 6a | Apr 21 | Mar 10 | Apr 28 | Jul 12 |
| Schaumburgzone 5b | Apr 30 | Mar 19 | May 7 | Jul 21 |
| Evanstonzone 6a | Apr 26 | Mar 15 | May 3 | Jul 17 |
| Arlington Heightszone 6a | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Bolingbrookzone 6a | Apr 20 | Mar 9 | Apr 27 | Jul 11 |
| Decaturzone 6a | Apr 14 | Mar 3 | Apr 21 | Jul 5 |
| Palatinezone 5b | Apr 25 | Mar 14 | May 2 | Jul 16 |
| Skokiezone 6a | Apr 26 | Mar 15 | May 3 | Jul 17 |
| Des Plaineszone 6a | Apr 16 | Mar 5 | Apr 23 | Jul 7 |
| Orland Parkzone 6a | Apr 20 | Mar 9 | Apr 27 | Jul 11 |
| Oak Lawnzone 6a | Apr 10 | Feb 27 | Apr 17 | Jul 1 |
| Mount Prospectzone 6a | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Berwynzone 6a | Apr 11 | Feb 28 | Apr 18 | Jul 2 |
| Tinley Parkzone 6a | Apr 23 | Mar 12 | Apr 30 | Jul 14 |
| Wheatonzone 5b | Apr 28 | Mar 17 | May 5 | Jul 19 |
| Normalzone 6a | Apr 25 | Mar 14 | May 2 | Jul 16 |
| Oak Parkzone 6a | Apr 11 | Feb 28 | Apr 18 | Jul 2 |
| Hoffman Estateszone 5b | Apr 30 | Mar 19 | May 7 | Jul 21 |
| Downers Grovezone 6a | Apr 28 | Mar 17 | May 5 | Jul 19 |
| Plainfieldzone 5b | Apr 20 | Mar 9 | Apr 27 | Jul 11 |
| Glenviewzone 6a | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Elmhurstzone 6a | Apr 16 | Mar 5 | Apr 23 | Jul 7 |
| Lombardzone 6a | Apr 28 | Mar 17 | May 5 | Jul 19 |
| Buffalo Grovezone 6a | Apr 19 | Mar 8 | Apr 26 | Jul 10 |
| Molinezone 5b | Apr 24 | Mar 13 | May 1 | Jul 15 |
| Crystal Lakezone 5b | May 1 | Mar 20 | May 8 | Jul 22 |
| Romeovillezone 6a | Apr 20 | Mar 9 | Apr 27 | Jul 11 |
What Illinois tomatoes need
Roma Tomato Seed (300+)
The determinate paste tomato: it ripens most of its crop inside a three-week window. That is a liability for eating and an enormous advantage for sauce day.
San Marzano Tomato SeedMust have
The paste tomato Italian canners actually use. Low seed cavity, low water, high pectin: it reduces to a sauce in half the time a slicer takes and never tastes thin.
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.
Seedling Heat Mat + Digital ThermostatMust have
Peppers germinate on soil temperature, not air temperature. At 65 °F a habanero takes a month and half of them rot; at 85 °F it is up in eight days. The thermostat is the half that matters.
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.
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.
5-Gallon Fabric Grow Bags, 5-Pack
Fabric pots air-prune roots and drain faster than a plastic pot can, which is the entire reason container tomatoes fail. Five gallons is the honest minimum for a pepper; a tomato wants ten.
Ocean Forest Potting SoilMust have
Pre-charged with enough nutrition to carry a transplant for its first month without feeding, which is exactly the window when most container plants stall.
Organic Tomato-Tone 3-4-6 with 8% CalciumMust have
The NPK ratio is the point: low nitrogen, higher potassium. Feed a tomato a high-nitrogen lawn fertiliser and you get a magnificent six-foot plant with four tomatoes on it.
Rot-Stop Blossom End Rot Concentrate
Blossom end rot is almost never a soil calcium shortage — it is a calcium *transport* failure caused by inconsistent water. A foliar calcium spray buys time while you fix the watering, which is the real cure.
58" Square Tomato Cages, 3-PackMust have
The conical wire tomato ring from the hardware store is 33 inches tall and an indeterminate San Marzano will laugh at it in July. Height and square geometry are what actually hold a loaded plant.
Drip Irrigation System with Timer, 16 Nozzles
Blossom end rot, split tomatoes and bitter fruit all trace back to the same thing: water that swings. A $50 timer removes the human from the loop and removes the swing.
Captain Jack Copper Fungicide, 16 oz
Early blight and septoria arrive with a wet July and work up the plant from the bottom. Copper is preventative — sprayed after you see it, you are already losing.
Thuricide BT Concentrate, 16 oz
Bacillus thuringiensis kills caterpillars and nothing else. For tomato hornworms — which can strip a plant in 48 hours — it is the most targeted tool that exists.
Stainless Steel Food Mill, 3 discsMust have
A blender pulverises tomato skins and seeds into the sauce, which is where bitterness comes from. A mill separates them out — no blanching, no peeling, no ice bath. It removes an entire hour from sauce day.
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Tomatoes in Illinois: questions
When should I plant tomatoes in Illinois?
Transplant around Apr 24 at the statewide median; across the state that date runs from Apr 14 in the warmest tenth of Illinois's ZIP codes to May 4 in the coldest. To cut the freeze risk to one year in ten, count from May 3 instead of the median last frost. Use the city table for your own town.
When do I start tomatoes seeds indoors in Illinois?
Around Mar 6 for Roma Tomato: 6 weeks before the statewide median last frost, on soil held at 75–85 °F.
When is the last frost in Illinois?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 17. In the warmest tenth of Illinois's ZIP codes the median last frost falls on or before Apr 7; in the coldest tenth, on or after Apr 27.
When will Illinois tomatoes be ready to harvest?
Roma Tomato planted on the statewide date is ready around Jul 8: 75 days from transplant.
More for Illinois
- When to plant peppers
- When to plant tomatillos
- When to plant basil
- When to plant onions
- When to plant cilantro
- When to plant carrots
- When to plant mustard greens
Tomatoes in every state → · Illinois frost dates → · How frost-date math works →