Planning a Vegetable Garden

Pick the site

The site decides more than any variety you choose. UW Extension’s checklist ¹:

• Sun: 6 to 8 hours of direct sun for fruiting crops like tomatoes, peppers, squash, and corn. Leafy greens and herbs tolerate a few hours less; beets, carrots, chard, kale, and turnips get by in part shade of 4 to 6 hours ¹.
• Drainage: well-drained soil, and not in a low spot, where cold air pools on still nights and frost comes earliest in fall and latest in spring ¹.
• Black walnut: keep at least 50 feet away ¹. Walnut roots and leaves release juglone, a compound that stunts or kills tomatoes and many other vegetables.
• Close to the house and to water, because a garden you walk past every day gets weeded and picked.

Lay it out

Sketch the garden on paper with north at the top, then ¹:

• Put perennials (asparagus, rhubarb, berries) along the north or northwest side, where they won’t be tilled and won’t shade anything.
• Put tall crops (corn, pole beans, trellised tomatoes and cucumbers) to the north of short ones so they don’t shade them.
• Run rows east to west.
• Group crops by plant family: tomato family (tomatoes, peppers, eggplant, potatoes), cabbage family (cabbage, broccoli, kale, radishes, turnips), squash family (squash, cucumbers, melons, pumpkins), and legumes (beans, peas).

Why families? Diseases and insects that attack one crop usually attack its relatives too, and they overwinter in the soil and debris where their hosts grew. Moving each family to a different bed every year, in a three- or four-year cycle, keeps them from building up, and legumes leave a little nitrogen behind for whatever follows. That’s the reason to lay the garden out as four equal beds from the start.

Time it by soil temperature

Wisconsin has roughly 110 frost-free days ¹, so timing matters. Use soil temperature, not the calendar; a soil thermometer is cheap.

Start indoors under lights:

• Cabbage family: 6 to 8 weeks before the last spring frost, mid to late March in southern Wisconsin ¹.
• Tomatoes, peppers, eggplant: 6 to 8 weeks before they go out, mid to late April ¹.
• Harden off transplants for 7 to 10 days, setting them outside a little longer each day ¹.

Plant outdoors (southern Wisconsin) ¹:

Pumpkins, melons, beans, and sunflowers go straight into the ground as seed after frost rather than being transplanted ¹. Plant later in central and northern Wisconsin, where spring arrives one to three weeks behind Madison.

Fertilize and mulch

Work compost in before planting, and side-dress fruiting crops again when tomatoes and cucumbers begin to set fruit ¹. Mulch after the soil warms with clean straw, untreated grass clippings, or shredded leaves to hold moisture and smother weeds; black plastic warms the soil 5 to 10 °F for heat-loving crops ¹.

What to take from this

Choose a site with 6–8 hours of sun and good drainage, out of frost pockets and 50 feet from black walnut. Put perennials on the north edge and tall crops north of short ones, run rows east–west, and group beds by plant family so you can rotate them each year. Start the cabbage family indoors in mid-March and tomatoes in mid-April, then plant by soil temperature: 50 °F for cool-season crops in late April, 60–70 °F with warm nights for warm-season crops around Memorial Day, and 70–75 °F for squash and melons in early June.