For most of Wisconsin, vegetables are planted based on frost dates and your USDA hardiness zone (generally Zones 3–5) rather than on the calendar alone. Cool‑season crops like peas, spinach, and broccoli go out earlier in spring, while warm‑season crops like tomatoes, peppers, and cucumbers usually wait until around late May or even early June, depending on where you are in the state.

Know your zone and frost date

  • Wisconsin ranges roughly from Zone 3 in the far north to Zone 5 in the south and along Lake Michigan.
  • Many southern and central locations have an average last spring frost around early to mid‑May, while northern areas may not be reliably frost‑free until late May or even June.
  • A common backyard rule of thumb is to set most warm‑season plants out sometime after Memorial Day, when late frosts are less likely, especially in cooler parts of the state.

When to plant cool‑season vegetables

Cool‑season crops tolerate light frosts and can be planted relatively early.

  • Leafy greens (spinach, lettuce, kale), peas, radishes, and carrots are often direct‑sown in late April to early May in much of Zones 4–5, and somewhat later in colder Zone 3 areas.
  • Carrots, for example, can be sown about 2–3 weeks before your local last frost date, in finely prepared soil, at about 0.5 inch deep.
  • Onions from sets or transplants are commonly planted in mid‑April in many Wisconsin areas, roughly a few weeks before the average last frost, once soil is workable.

When to plant warm‑season vegetables

Warm‑season crops are damaged by frost and need warm soil.

  • Tomatoes are typically started indoors 4–6 weeks before your local last spring frost, then transplanted outdoors after danger of frost has passed and soils have warmed, often late May in much of Wisconsin.
  • Peppers, cucumbers, zucchini, squash, and beans are also set out or sown after the last frost date; many gardeners in cooler regions wait until around or just after Memorial Day for safety.
  • Potatoes in northern Wisconsin can be planted about two weeks before the average last frost, once soil temperatures are above about 40°F to reduce rot risk.

Fall planting window

Fall gardening in Wisconsin is shorter, so timing is tight.

  • Many short‑season cool crops (lettuce, radishes, some brassicas) are sown in July or early August so they mature before the first hard frost, which can come in September or October depending on location.
  • Gardeners often aim to have most fall crops maturing at least a couple of weeks before typical first frost, since fall gardening in Zones 3–5 is essentially a race against returning cold.

Practical tips for your exact location

  • Check a local planting calendar (often organized by city or county extension) that lists indoor seed‑starting dates and outdoor planting windows for your specific frost‑free period of about 110 frost‑free days on average in Wisconsin.
  • Watch short‑term forecasts each spring: if a late cold snap is expected, be ready with row covers or to delay planting tender crops by a week.

Information gathered from public forums or data available on the internet and portrayed here.