In Michigan, you can plant potatoes once the soil temperature reaches at least 45°F, which typically falls between mid-April in southern counties and mid-May in the Upper Peninsula. Potatoes are a cool-season crop that thrives in Michigan’s climate, and the state is actually the nation’s leading producer of summer “new” potatoes and chip-processing varieties. With the right timing, soil prep, and a little attention through the season, a home garden can produce a solid harvest.
When to Plant
Soil temperature matters more than the calendar. Stick a soil thermometer 4 inches deep in the morning: if it reads above 45°F, you’re good to go. Planting into cold, wet soil is the most common early-season mistake. It causes seed pieces to rot before they ever sprout. On the other hand, planting into cool but dry soil just delays emergence, so a little patience pays off.
For most of Lower Michigan, that 45°F threshold arrives sometime in late April. Northern Lower Michigan and the Upper Peninsula often don’t hit it until early to mid-May. If you’re unsure, waiting an extra week is always safer than rushing. Potatoes grow best when daytime temperatures stay between 65°F and 80°F with nights in the 55°F to 65°F range, which describes a typical Michigan June and July perfectly.
Choosing the Right Varieties
Michigan grows four main types of potatoes commercially, and all of them do well in home gardens. Round whites are the state’s most popular type, great for boiling, roasting, and making chips. Red-skinned varieties are a Michigan specialty, often harvested young as “new” potatoes with tender, thin skins. Russets are the classic baking potato, with a fluffy interior that holds butter well. And yellow or “golden” potatoes have a naturally buttery flavor that’s made them increasingly popular.
For a home garden, planting a mix gives you the most flexibility in the kitchen. Look for certified seed potatoes at a garden center rather than using grocery store potatoes, which may carry disease or be treated to inhibit sprouting.
Preparing Your Soil
Potatoes prefer loose, well-drained soil. If your garden has heavy clay (common in parts of southern Michigan), work in several inches of compost before planting to improve drainage. Sandy soils in western and northern Michigan drain well naturally but may need extra organic matter to hold moisture and nutrients.
Potatoes do best in slightly acidic soil, generally around a pH of 5.0 to 6.5. Avoid adding lime to your potato patch right before planting, as higher pH encourages a rough skin condition called scab. If you’ve been liming other parts of your garden, plant your potatoes in an area that hasn’t been treated recently. A basic soil test through your county MSU Extension office will tell you exactly where your pH stands.
Cutting and Preparing Seed Pieces
A few days before planting, cut larger seed potatoes into pieces roughly 2.5 ounces each, about the size of a golf ball. Each piece needs at least two “eyes,” the small indentations where sprouts emerge. Let the cut pieces sit in a cool, dry spot for one to two days so the cut surfaces form a dry seal. This step reduces the chance of rot once they’re in the ground.
Small seed potatoes (under 2 ounces) can go in whole. In fact, planting whole seed is a good strategy if your soil tends to stay cool and damp in spring, since there’s no exposed cut surface for bacteria to attack.
Planting Depth and Spacing
Dig a trench about 5 inches deep, which is the standard planting depth. Place seed pieces cut-side down with the eyes facing up, spacing them about 9 inches apart within the row. Leave roughly 34 inches (just under 3 feet) between rows to give yourself room for hilling later.
Shallower planting at 3 inches works in heavier soils where you want the seed piece closer to warmth, but it means more aggressive hilling later. Deeper planting at 7 inches can work in sandy soils but may slow emergence. For most Michigan home gardens, that 5-inch depth hits the sweet spot. Cover the seed pieces with soil and water gently.
Hilling Through the Season
Hilling is the most important maintenance task for potatoes, and it’s simple once you understand the purpose. Potatoes form along the buried stem above the seed piece. The more stem you bury, the more potatoes you get. Any tuber exposed to sunlight turns green and produces a mildly toxic compound, so hilling also protects your crop.
When the plants are about 6 inches tall, mound 3 to 4 inches of soil (or a mix of soil and straw) around the base of each plant, leaving just the top few inches of foliage exposed. Repeat this every two to three weeks as the plants grow, pulling soil from between the rows or adding compost, straw, or shredded leaves. Most gardeners hill two to three times total before the plants flower and fill in the rows.
Watering and Feeding
Potatoes need about 1 to 2 inches of water per week, especially during tuber formation, which starts around flowering time. Inconsistent watering leads to knobby, misshapen tubers or hollow centers. A soaker hose laid along the row works well because it keeps the foliage dry, which helps prevent fungal diseases.
If you worked compost into the soil before planting, your potatoes may not need much additional fertilizer. A side dressing of a balanced granular fertilizer at first hilling can give them a boost. Avoid heavy nitrogen late in the season, as it encourages leafy top growth at the expense of tuber development.
Watching for Colorado Potato Beetles
The Colorado potato beetle is the most destructive insect pest for potatoes in the eastern United States, and Michigan is no exception. Adults are round, yellow-orange beetles with black stripes on their backs. They lay clusters of bright orange eggs on the undersides of leaves, and the larvae are plump, reddish-pink grubs with black spots along their sides.
Check your plants regularly starting in late June. The first generation of larvae typically peaks in early July. Hand-picking adults, eggs, and larvae into a bucket of soapy water is effective in a small garden. For larger patches, a naturally occurring bacterial spray containing Bacillus thuringiensis (Bt) can suppress larvae effectively with a couple of applications. Rotating where you plant potatoes each year also helps, since the beetles overwinter in the soil near the previous year’s crop.
Preventing Late Blight
Late blight is the same disease that caused the Irish Potato Famine, and it still shows up in Michigan. It spreads fast in cool, wet weather, producing dark, water-soaked spots on leaves that quickly turn brown and papery. Infected tubers develop firm, brownish-purple patches under the skin.
Your best defenses are cultural. Space plants far enough apart for good air circulation. Water at the soil line instead of overhead. Remove and destroy any volunteer potato plants from last year, since they can harbor the pathogen. If late blight has been reported in your area (MSU Extension often issues alerts), a preventive copper-based fungicide applied early can help protect foliage. Starting with certified disease-free seed potatoes eliminates the most common source of infection in home gardens.
Harvesting at the Right Time
Wait until the vines have completely died back before harvesting your main crop. Dead vines are the clearest sign that the tubers have finished growing. If you want “new” potatoes, you can reach into a hill and steal a few small ones once the plants flower, but leave the rest to mature fully.
Before digging up everything, unearth one test hill. Rub the skin of a potato with your thumb. If the skin is thick and stays firmly attached, they’re mature. If the skin is thin and rubs off easily, leave the rest in the ground for another few days and check again. Use a garden fork rather than a shovel to dig, starting about a foot from the base of the plant to avoid slicing tubers.
Curing and Storing
Freshly dug potatoes need to cure before long-term storage. Spread them in a single layer in a dark spot with temperatures between 45°F and 60°F and let them sit for about two weeks. This hardens the skins and lets minor nicks from harvesting heal over, which prevents rot during storage.
After curing, move your potatoes to a cool, dark, humid location. A Michigan basement or root cellar in the 38°F to 45°F range is ideal. Don’t wash them until you’re ready to use them, since moisture shortens storage life. Stored properly, most varieties will keep for several months, easily carrying you into winter.