To make potatoes sprout, place them in a bright, cool spot with good air circulation for four to six weeks. The ideal temperature is around 70°F with high humidity. This process, called chitting or green sprouting, produces short, sturdy sprouts that are ready to plant and give your crop a head start in the garden.
Why Light and Temperature Matter
Potatoes naturally enter a dormancy period after harvest. Depending on the variety and storage conditions, this dormancy lasts anywhere from one to fifteen weeks. During that time, the buds on the surface won’t grow even under perfect sprouting conditions. Once dormancy breaks, the “eyes” of the potato begin pushing out shoots.
Light is the key ingredient that separates strong sprouts from weak ones. Potatoes left somewhere warm and dark produce long, pale, brittle sprouts that snap off easily when you try to plant them. Potatoes exposed to light develop short, stubby, greenish sprouts (typically under an inch long) that are much tougher and emerge faster once they’re in the ground. The green color comes from chlorophyll production triggered by light exposure, and it’s a sign of a healthy sprout.
Step-by-Step Sprouting Instructions
Start by choosing firm, healthy-looking potatoes with no soft spots, discoloration, or foul smell. Watersoaked or slimy patches indicate bacterial rot. Dark, sunken areas with reddish-brown flesh underneath suggest blight. Small black specks that look like dirt but won’t wash off are a fungal issue called black scurf. Any of these problems mean the tuber should be discarded.
Stand each potato upright in an egg carton or a shallow tray with the end that has the most eyes facing up. Most potatoes have a cluster of eyes concentrated at one end (the “rose end”) and fewer at the opposite end where the tuber was attached to the plant. Place the carton on a windowsill or in any bright, frost-free room. An unheated spare bedroom, a porch, or a garage that stays above freezing all work well.
Turn the potatoes occasionally to encourage even sprouting across the surface. You’re aiming for sprouts about three-quarters of an inch to one inch long, which typically takes four to six weeks. Once the sprouts reach that size, the potatoes are ready for the soil.
Store-Bought Potatoes vs. Seed Potatoes
Grocery store potatoes are commonly treated with a chemical sprout suppressant that blocks cell division in the buds. This treatment is specifically designed to keep potatoes from sprouting during months of commercial storage. While some store-bought potatoes will eventually sprout anyway (especially organic ones, which are less likely to be treated), many simply won’t cooperate no matter how perfect your setup is.
Seed potatoes sold by garden centers and seed suppliers have never been treated with sprout inhibitors. They’re also certified disease-free, which matters because potatoes are vulnerable to soil-borne diseases that carry over from infected tubers. If you’re sprouting potatoes with the goal of planting a productive garden crop, seed potatoes are the reliable choice.
How Pre-Sprouting Helps Your Harvest
Chitting isn’t strictly necessary, but it gives you measurable advantages. Pre-sprouted potatoes emerge from the soil faster, develop their leafy canopy sooner, and set tubers earlier in the season. Plants grown from chitted potatoes tend to produce more tubers per plant, though the individual potatoes are often smaller. For gardeners in short-season climates, that earlier maturity can be the difference between a full harvest and one cut short by frost.
There’s a pest management benefit too. Potato beetles and leafhoppers tend to emerge later in summer. Because chitted potatoes mature faster, the plants can get ahead of peak pest pressure. Later-maturing potato varieties generally need a longer chitting period than early varieties to see these benefits, so plan accordingly.
Cold Storage Before Sprouting
If you have seed potatoes but aren’t ready to start chitting yet, cold storage changes what happens when you eventually do. Potatoes stored at cool temperatures (around 40°F) for several weeks and then moved to warmth sprout differently than potatoes kept at room temperature the whole time. The cold period weakens the dominance of the single top bud, so instead of one strong sprout at the tip, you get multiple sprouts emerging from different eyes across the tuber. More sprouts means more stems per plant, which generally means more (but smaller) tubers at harvest.
Cutting Sprouted Potatoes Before Planting
Small seed potatoes, roughly the size of a golf ball or smaller, can go into the ground whole. Larger tubers should be cut into pieces so each piece weighs about 1.75 ounces, roughly the size of a small egg. Every piece needs at least one eye with a sprout. Here are the general guidelines based on tuber size:
- Under 1.5 ounces: Too small to plant. Discard or eat these.
- 1.5 to 3 ounces: Cut in half.
- 5 to 7 ounces: Cut into three pieces.
- Over 10 ounces: Cut by hand into four or more blocky pieces.
Cut for blocky shapes rather than thin slabs. Blocky pieces retain more moisture and have better contact with soil. Some potato varieties have eyes clustered unevenly, so you may need to cut slightly larger pieces to ensure each one has a viable sprout. After cutting, let the pieces sit for a day or two in a cool spot so the cut surfaces dry and form a thin skin. This reduces the risk of rot once they’re in the ground.
Timing Your Sprouts for Planting
Count backward from your expected planting date. In most regions, potatoes go into the ground two to four weeks before the last expected frost, once soil temperatures reach about 45°F. Since chitting takes four to six weeks, that means starting the process in late winter for a spring planting. If you’re in a cold climate where you plant in mid-May, begin chitting in late March or early April. Warmer regions with earlier planting windows should start sooner.
If your sprouts get too long before planting time, move the potatoes to a cooler (but still frost-free) location to slow growth. Sprouts longer than about an inch become increasingly fragile and more likely to break during handling.