Tomatoes go in the ground once the danger of frost has passed, and for the Chicago area that means NOAA’s National Centers for Environmental Information (NCEI) puts the last spring freeze, using its 1991-2020 climate normals, between April 11 and April 22. Gardeners farther from the city, especially in northern Illinois or at higher elevation, should expect that date to land later. Check your own county’s frost data through Illinois Extension before you set out a single transplant.
When to plant Tomatoes in Illinois
Chicago’s frost window, April 11 to April 22, is the fixed point everything else here counts backward or forward from. Seed-starting dates, hardening-off schedules, even which variety you can realistically ripen before a September cold snap all hinge on that stretch, because tomato seedlings need six to eight weeks of growth before they’re sturdy enough to go outside. Gardeners south or north of Chicago just slide the whole calendar to match their own local frost date.
Starting seeds indoors
Tomato seedlings need six to eight weeks of growth under lights or on a bright windowsill before they’re ready to go outside. Counting back six to eight weeks from the Chicago window of April 11 to April 22 puts indoor sowing at roughly mid-February to mid-March: eight weeks back from April 11 lands near mid-February, and six weeks back from April 22 lands near mid-March. Gardeners working from a later, more realistic local frost date should push this sowing window back by however many weeks their own frost date runs behind Chicago’s.
Hardening off and transplanting outside
Once seedlings have a set or two of true leaves and the forecast looks steady, harden them off over seven to ten days. Set them outside in a sheltered, part-shaded spot for a couple of hours at a time, adding an hour or two of exposure and direct sun each day. Transplant only after the local frost window has passed, and many Illinois gardeners add another week of buffer before committing plants to the open garden, since a stray late freeze can kill a tomato seedling overnight. Keep a frost blanket on hand through early May as cheap insurance against a cold snap the forecast didn’t catch in time.
Sun Gold, at 57 days from transplant, shows how the calendar plays out from there. Set out right after the Chicago frost window closes in late April, and the first ripe fruit lands in mid to late June. Set out in mid-May instead, and the first fruit doesn’t arrive until July. Longer-season varieties push that first-harvest date further into summer, which matters when weighing a 60-day cherry tomato against an 85-day paste tomato for a given piece of ground.
Soil and site preparation
Tomatoes want six to eight hours of direct sun and good airflow between plants, which cuts down on the fungal diseases that thrive in still, humid air. Pick the sunniest, most open part of the yard rather than a corner that gets dappled shade from a fence or a tree line for part of the day.
Building the bed
Much of Illinois gardens on heavy, clay-based prairie soil that drains slowly and warms up late in spring. Work two to three inches of compost into the top six to eight inches of soil in the weeks before planting, not the day of, so it has time to settle and start feeding the soil biology before roots move in. If a bed stays wet and sticky a full day after rain, consider raised beds or raised rows eight to twelve inches high. That lifts the root zone above standing water and lets the soil warm faster in spring, which matters more for a heat-loving crop in a state where spring stays cool into April.
Spacing and testing
Space indeterminate varieties 24 to 36 inches apart in rows three to four feet apart, and set determinate varieties a little closer, 18 to 24 inches, since they stay more compact. Get a soil test done before you amend rather than guessing at lime or fertilizer needs. Extension offices around the state run soil testing programs that show where pH and nutrient levels actually stand, which is worth checking every three to four years even in a bed that’s grown tomatoes for years without trouble.
Varieties that suit Illinois
With spring frost risk running into late April at Chicago and no single fall freeze date to plan a whole season around, the safest approach is to lean on days-to-maturity as a planning tool. Add a variety’s catalog days-to-maturity to whatever transplant date you land on, then weigh the total against how long your own garden’s season typically runs, using your local extension office or your own garden records as the check.
Fast-maturing varieties
Sun Gold (57 days from transplant) and Sakura (55 days) are among the quickest cherry tomatoes to bear fruit, useful for a harvest that starts well ahead of the main-season slicers. Jasper (60 days) and Juliet (60 days) mature at a similar pace and both carry resistance to late blight and early blight, two fungal diseases that spread fast in humid Illinois summers. Supersweet 100 (60 days) rounds out the early cherry options and resists verticillium and fusarium wilt.
Main-season and paste varieties
Celebrity Plus (78 days, determinate) and Big Beef Plus (72 days, indeterminate) both carry resistance to nematodes, gray leaf spot and tomato mosaic virus, useful in a bed that’s grown tomatoes for several years running. Amalfi (68 days, determinate) is a paste tomato bred with disease resistance built in, while San Marzano II (78 days, indeterminate) is a classic sauce tomato without that package, better reserved for a bed with a clean disease history. Tiren (75 days) and Granadero (75 days) both resist verticillium or fusarium wilt along with mosaic virus.
Heirlooms and long-season varieties
Cherokee Purple (72 days), Brandywine (78 days) and Amish Paste (85 days) carry no disease resistance package and take longer to bear, which raises the stakes if a wet, cool spring pushes transplanting later than planned. They reward the wait with flavor the resistant hybrids don’t quite match, but they’re a better bet for a bed with a track record of good tomato seasons than for a first attempt in new ground.
| Variety | Days to maturity | Type | Notable resistance |
|---|---|---|---|
| Sun Gold | 57 | Indeterminate | Tobacco Mosaic Virus, Fusarium Wilt race 1 |
| Sakura | 55 | Indeterminate | Nematodes, Tomato Mosaic Virus, Fusarium Wilt races 1, 2 |
| Jasper | 60 | Indeterminate | Late Blight, Early Blight |
| Juliet | 60 | Indeterminate | Late Blight, Early Blight |
| Supersweet 100 | 60 | Indeterminate | Verticillium Wilt, Fusarium Wilt race 1 |
| Amalfi | 68 | Determinate | Nematodes, Late Blight, Early Blight |
| Celebrity Plus | 78 | Determinate | Nematodes, Gray Leaf Spot, Tomato Mosaic Virus |
| Big Beef Plus | 72 | Indeterminate | Nematodes, Gray Leaf Spot, Tomato Mosaic Virus |
| San Marzano II | 78 | Indeterminate | None listed |
| Tiren | 75 | Indeterminate | Verticillium Wilt, Tomato Mosaic Virus, Fusarium Wilt race 1 |
| Granadero | 75 | Indeterminate | Nematodes, Verticillium Wilt, Tomato Mosaic Virus |
| Cherokee Purple | 72 | Indeterminate | None listed |
| Brandywine | 78 | Indeterminate | None listed |
| Amish Paste | 85 | Indeterminate | None listed |
What to plant alongside
Basil planted at the base of tomato plants doesn’t have strong research behind the old claim that it improves flavor, but it draws in pollinators and predatory insects when it’s allowed to flower, and it makes use of the same bed space without competing hard for nutrients. Borage does something similar, and its blue flowers pull in bees that help set fruit on top of the pollination tomatoes already manage through wind and their own flower structure.
Marigolds get credited with repelling nematodes and whiteflies, but the evidence is thin. Some marigold varieties do suppress root-knot nematodes in soil, though the effect shows up over a full season of marigolds grown as a cover crop, not from a few plants tucked between tomato seedlings. Plant them for the pollinator draw and the color, not as pest control.
Good neighbors
Onions and chives along the edge of a tomato bed take up little space, and their smell is thought to confuse some pest insects that hunt by scent, though the research on that is mixed too. Carrots make efficient use of the ground between young tomato plants early in the season, before the tomato canopy fills in and shades them out.
Keep these away
Corn and tomatoes both attract the corn earworm, known on tomatoes as the tomato fruitworm, so planting them side by side gives the pest a bridge between two host crops. Potatoes and tomatoes are both nightshades that share susceptibility to early blight and late blight, and growing them in touching beds spreads spores between the two. Keep brassicas like cabbage and broccoli in a separate bed too. They compete for the same nitrogen without offering tomatoes anything in return.
Watering, feeding and support
Watering and mulching
Tomatoes want a steady one to two inches of water a week, delivered at the soil level rather than overhead, since wet leaves left standing overnight are exactly the humid environment fungal disease needs. Soaker hoses or drip line under a layer of mulch do the job better than a sprinkler. Straw or shredded leaf mulch three to four inches deep keeps soil moisture even between waterings and stops the wild swings, wet then bone dry, that cause blossom end rot and fruit cracking. Consistency matters more than volume: a plant soaked deeply once a week does better than one watered a little every day.
Feeding
Work a balanced fertilizer or a few inches of finished compost into the soil at planting, then hold off on more nitrogen until the first fruit sets. Tomatoes fed too much nitrogen too early put their energy into leafy growth instead of flowers, ending up as a lush plant with little fruit to show for it. Once fruit is sizing on the lower trusses, a side dressing lower in nitrogen and higher in phosphorus and potassium carries the plant through the rest of the season.
Staking and pruning
Indeterminate varieties like Sun Gold, Big Beef Plus and Brandywine keep growing and setting fruit until frost, and need a stake, cage or trellis strong enough to hold a plant that can top six feet by late summer. Determinate varieties like Celebrity Plus and Amalfi stop growing once they set a fixed number of fruit clusters and stay more compact, so a standard tomato cage usually holds them fine. Pinch out suckers, the small shoots that form where a side branch meets the main stem, on indeterminate varieties to keep the plant from turning into a tangled mass that blocks airflow and hides ripening fruit. Determinate varieties need little to no pruning, since removing growing points cuts into the fixed number of trusses they were bred to produce.
Common problems
Most tomato problems in a home garden trace back to water, temperature swings, or one of a handful of fungal diseases that show up somewhere in the state every summer.
Physiological problems
Blossom end rot shows up as a flat, sunken, leathery brown-black patch on the bottom of the fruit, opposite the stem. It’s caused by a local calcium shortage inside the fruit itself, usually triggered by inconsistent watering rather than a true lack of calcium in the soil. Even out the watering schedule and the next flush of fruit is usually fine. Cracking, concentric rings or splits radiating out from the stem, happens when a dry spell is followed by a heavy rain or a big drink of water, and the fruit swells faster than its skin can stretch. Poor fruit set, where flowers drop without forming fruit, is common during a stretch of very warm nights or cool, cloudy weather that keeps pollen from shedding properly, and it tends to pass once temperatures settle back into range.
Diseases
Fusarium and verticillium wilt are soil-borne fungi that clog a plant’s water-conducting tissue, showing up as yellowing that starts on lower leaves, often on just one side of the plant, followed by wilting that doesn’t recover overnight. There’s no cure once a plant is infected. Resistant varieties are the main defense: look for the F and V codes on plant tags, carried by varieties like Supersweet 100, Tiren and Granadero. Early blight shows up as dark, concentric-ringed spots on lower, older leaves first, working upward through the season. Late blight moves faster and looks different, with large, greasy, water-soaked patches on leaves and stems that can collapse a plant within days in cool, wet weather. Jasper and Juliet carry resistance to both. Gardeners just over the state line dealing with the same fusarium and verticillium pressure can compare notes in our guide to growing tomatoes in Indiana.
Pests
- Tomato hornworms: a stout green caterpillar as thick as a finger, with white diagonal stripes and a small horn on the tail end, capable of stripping a branch of leaves overnight
- Aphids: small, soft-bodied insects clustered on the undersides of leaves and new growth, often trailing sticky honeydew
- Whiteflies: tiny white insects that flutter up in a cloud when a leaf is disturbed
- Cutworms: gray-brown grubs that sever young transplants right at the soil line, usually at night
Hand-picking hornworms works fine at home-garden scale, and a strong spray of water or insecticidal soap knocks back aphids and whiteflies. A cardboard collar around the stem of a new transplant stops cutworms cold. Check the undersides of leaves weekly, since nearly all of these problems are far easier to manage caught early than after they’ve spread through the whole plant.
Pests that actually show up in Illinois
Three insects on Illinois’s pest list actually bite into a tomato plant. The rest belong to other crops in the vegetable patch, and it is worth knowing that if you grow more than tomatoes. Squash vine borer and squash bug work on squash and other cucurbits, bagworm targets evergreens and shrubs, and spotted lanternfly goes after grapevines and tree of heaven. The University of Illinois Extension tracks all of them under one pest list, but a tomato grower only needs to watch three names.
Japanese beetle shows up first as skeletonized leaves, the green tissue chewed away between veins so the leaf looks like lace. University of Illinois Extension notes adults emerge in late June and stay active through July and August, the same stretch when tomato foliage is thickest. Hand-picking into a bucket of soapy water in the morning, when beetles are sluggish, controls small infestations without reaching for a spray.
Colorado potato beetle feeds on tomato foliage as readily as on potato, stripping leaves down to the stem starting from the growing tip. Egg-laying peaks in mid-June and the state sees two to three generations a season, so a plant that looks fine in June can be stripped by August if the first wave goes unchecked. Check the undersides of leaves for the orange-yellow egg clusters and crush them before they hatch. That single habit does more than any product on the shelf.
Brown marmorated stink bug leaves a different mark: cloudy, discolored patches just under the skin of the fruit itself, where it pierced the tomato to feed. Damage tends to build through the same July-August window as the other two. Row cover over young plants keeps early populations out, though it has to come off once flowers open and pollinators need access.
Jumping worms do not touch the plant at all, but they wreck the soil it grows in, chewing through organic matter and leaving behind a loose, grainy castings layer that drains too fast and holds no nutrients. University of Illinois Extension has confirmed them in 49 of the state’s 102 counties. There is no treatment once they are established, so buying bagged compost and mulch from a source that heat-treats it is the only real defense.
Harvest and end of season
Pick tomatoes once they’ve reached full color for the variety: the deep red of Celebrity Plus, the near-black red-purple of Cherokee Purple, or the golden-orange of Sun Gold. Fruit that’s fully colored but still firm ripens fine off the plant and is less likely to split or draw pests than fruit left to over-ripen outside.
Storing and ripening
Keep ripe tomatoes at room temperature out of direct sun rather than in the refrigerator, since cold storage breaks down texture and dulls flavor. Fruit still showing green with a hint of color starting, often called the breaker stage, will finish ripening indoors on a counter or in a paper bag over the following week.
As frost approaches
NOAA’s frost data for this region covers the spring side of the season, so there’s no single fall freeze date to plan around here. Track your own area’s overnight lows as autumn moves in, and once a frost is forecast, pick everything left on the vine, including fruit still fully green. Wrap individual green tomatoes in newspaper and store them in a cool, dark spot, checking weekly and pulling out any that start to ripen or rot. Most will color up gradually over several weeks. Pulling whole plants by the roots before a hard freeze and hanging them upside down in a garage or shed is another option, and it tends to let fruit keep ripening on the vine a while longer than picking fruit individually does.
Local help
Frost dates, soil test results and disease pressure all vary by county, and the Chicago-based figures in this guide are a starting point, not a local forecast. Illinois Extension runs county offices across the state with local planting information, soil testing programs and diagnostic help for a wilting or spotted plant you can’t identify. Find your county’s office through Illinois Extension before you lock in a planting date this spring.
Where to Go From Here
Everything above is the overview — the three pages behind it go deeper on the parts that actually decide whether you get tomatoes or excuses. If you want the real math instead of a rule of thumb, Tomato Planting Dates in Illinois works backward from the April 11 to April 22 last-freeze window near Chicago, so you’re not guessing whether a 55-day cherry and an 85-day paste tomato should go in on the same day. Once timing’s sorted, Tomato Varieties That Ripen in Time in Illinois lays out which tomatoes actually finish before frost, matched to the length of season you’ve really got, not the one on the seed packet’s optimistic end. And because something is always coming for the plants once they’re in the ground, Tomato Pests in Illinois walks through what shows up and when — cutworms right after transplant, and whatever’s next on the calendar after that. Read them in that order and you’ve covered when to plant, what to plant, and what to watch for once it’s growing.
Common questions
Can I plant tomatoes before the last frost date?
You can, but it’s a gamble. A late freeze will kill an unprotected seedling outright, and even a close call with cold, wet soil below the mid-50s can stunt growth for weeks afterward without ever showing frost damage. If you’re set on an early start, keep frost cloth or buckets ready to cover plants overnight.
How many tomato plants do I need for a family of four?
It depends more on what you’re growing them for than on a fixed number. Four to six plants mixing one or two cherry varieties with a couple of slicers or paste tomatoes usually covers fresh eating through the summer, while anyone planning to can sauce should figure closer to eight to twelve paste plants for a decent batch.
Why are my tomato leaves curling?
Upward curling of older leaves with the plant otherwise looking healthy and setting fruit normally is usually a physiological response to heat, drought stress or heavy pruning, and it isn’t a disease. Curling paired with yellowing, mottling or stunted new growth is more concerning and worth checking against wilt or virus symptoms, or against nearby herbicide use, since drift can cause distinctive curling too.
Can I grow tomatoes in containers?
Yes, and determinate varieties like Celebrity Plus or Amalfi tend to handle container life better than sprawling indeterminate types. Use a pot of at least five gallons, more for a full-size slicer, since containers heat up and dry out faster than garden soil and need more frequent watering, sometimes daily in hot stretches.
Is it too late to plant tomatoes if I missed the spring window?
Not necessarily, if you switch to a fast-maturing variety. Sun Gold at 57 days or Sakura at 55 days can still produce a crop from a later transplant, but count forward from your transplant date and check the total against your county’s typical fall conditions through Illinois Extension before committing, since a late planting leaves no room for a slow finish.