Wisconsin · zones 4a–5b
When to plant sweet corn in Wisconsin.
Sow between May 12 to Jul 13 in a typical year, keyed to Wisconsin's median last frost around May 5. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Corn dates for a typical Wisconsin season.
Direct sow
May 12 to Jul 13
Keyed to the ~May 5 last frost. Sow 1.5" deep, 12" apart.
Harvest
~75 days later
~1 lb per plant over ~1 weeks.
Wisconsin spans more than one climate: Zone 5 is the most common zone, but the state runs 4a to 5b. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Wisconsin growing notes
Sweet corn built Wisconsin's canning industry. Here is how home rows differ.
A crop grown for the cannery, adapted for the yard
Wisconsin has canned and frozen as much sweet corn as almost any state in the country for over a century, and that processing industry shaped which varieties farm supply stores here actually stock: reliable, disease resistant hybrids bred to ripen evenly rather than novelty types. A home garden can lean into either direction. Golden Bantam, the old open pollinated standard from the early 1900s, still performs well in Wisconsin gardens and lets you save your own seed. Bodacious, a modern sugary enhanced hybrid, trades that seed saving ability for noticeably sweeter, more tender kernels.
Sweet corn's biggest planting mistake in a home garden is not variety, it is geometry: plant it in short single rows and wind pollinated ears fill in half empty, but a block at least 4 rows wide lets pollen drift sideways onto silks instead of blowing past them. If space forces a single long row, collect pollen in a paper bag from the tops at mid morning and dust it straight onto the silks every second day while tassels appear.
Keep your sugary types apart
Different sweet corn types cross pollinate freely, and a supersweet variety planted too close to a standard or sugary enhanced type loses its sweetness in the kernels that result, turning starchy and tough by the time you shuck it. The safe distance most extension guides recommend is 250 feet between different types, or staggering the plantings so their pollen sheds at least 2 weeks apart if your lot cannot spare that much room.
A 75 day variety fits comfortably inside Wisconsin's roughly 5 month frost free window with room to spare for succession sowing, so plant in 2 or 3 batches 2 weeks apart instead of one big block, and you stretch fresh eating corn across most of the summer rather than facing 200 ears ripe on the same Tuesday.
Earworm, borer, and the raccoon problem nobody puts in the extension bulletin
The earworm's whole strategy depends on silk: eggs go onto it, and the hatchling follows that strand straight down to the ear tip. Wait until silks have wilted and started browning, usually 3 to 5 days after they first appear, then work a few drops of mineral oil into the silk channel at the tip of each ear; oiling green, actively pollinating silk too early blocks pollen tubes from reaching the kernels and leaves you with a bare, unfilled ear tip instead of a protected one. European corn borer works the stalk instead, tunneling in below the ear and occasionally causing the whole plant to snap in wind; scout for small round entry holes with sawdust like frass around them.
None of that beats the actual top predator of Wisconsin sweet corn, which is raccoons, and they know the ripening window better than most gardeners do. An electric fence wire strung at 6 and 12 inches around the patch the week ears start to fill silk stops them far more reliably than any scent deterrent, and it is worth setting up before you find the whole row flattened the night before you planned to pick.
In Wisconsin: watch for
The pests that find sweet corn here.
A middle-length season, about 151 frost-free days, means sweet corn overlaps corn earworm for a stretch each summer. Check plants every week or two and treat early.
Caterpillars feeding down in the tip of the ear.
Organic fix: A few drops of oil on the silk; Bt on the silks.
Broken tassels and frass-filled holes in the stalk.
Organic fix: Bt on young plants; cut and destroy stalks after harvest.
Clusters on the tassels and upper leaves.
Organic fix: Usually minor; insecticidal soap if heavy.
Fall armyworm
Ragged holes through the unfurling whorl leaves, with sawdust-like droppings down in the funnel.
Organic fix: Check whorls weekly before tassel; Bt or spinosad while the caterpillars are still small.
Cinnamon-brown powdery pustules breaking out on BOTH sides of the same leaf, lower leaves first, darkening as they age.
Organic fix: Water at the ground rather than overhead, and choose resistant varieties next season; sprays are rarely worth it.
Your season math: Wisconsin gives sweet corn about 151 frost-free days, and it needs roughly 75 days to a first harvest. That fits about 8 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting sweet corn in Wisconsin: questions
When should I plant sweet corn in Wisconsin?+
In a typical Wisconsin year, sow sweet corn between May 12 to Jul 13, keyed to the state's median last frost around May 5. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Wisconsin?+
Wisconsin spans zones 4a–5b, mostly zone 5. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many sweet corn plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.