How to Grow Potatoes: Planting, Hilling and Harvest Timing

At a glance

When to plant potatoes, by zone

Potatoes are a cool-season crop. University of Maryland Extension says to plant once the soil is at least 45°F; potatoes withstand light frosts but not heavy frost or freezing, and seed pieces can rot if planted into prolonged cold, damp soil. In Georgia, UGA Extension notes the 45°F mark usually arrives before the last spring frost and that potatoes emerge best once soil is above 50°F. Find your dates with the frost date lookup.

These windows apply the soil-temperature rule by zone and are approximate. Why the rush: University of Illinois Extension notes tubers form best at soil temperatures of 60–70°F and fail to form when soil reaches 80°F, so a crop planted late into summer heat yields less.

Choose and prepare seed potatoes

Start with certified seed potatoes. University of Maryland Extension and University of Illinois Extension recommend certified, disease-free seed. UMD notes supermarket potatoes and last season's garden tubers can carry diseases without showing symptoms. Seed potatoes should be firm and unsprouted when you buy them.

Pick by maturity, not just color. Seed catalogs group cultivars as early, mid-season or late. UMD suggests growing an early variety for new potatoes and a medium- to late-maturing variety for storage; Illinois notes late potatoes are best for winter storage.

Green-sprout if you want a head start. UMD describes keeping whole tubers in the dark at room temperature until they sprout, then exposing them to light to keep sprouts short before cutting and planting. UGA suggests two to three weeks in a single layer in a warm room that gets some sun.

Cut large tubers into seed pieces. Each piece should weigh about 1½ to 2 ounces with at least one good eye (University of Maryland Extension; University of Illinois Extension); UGA likens a 1.5-ounce piece to a small egg. Small whole seed potatoes can be planted as is. UMD and Nebraska Extension advise letting cut pieces dry for a day or two (a few days, per UMD) so the cuts heal before planting.

How to plant potatoes: step by step

1. Pick a sunny spot (at least 6 hours of direct sun, 8–10 preferred, per UMD) with fertile, well-drained soil that has not grown potatoes, tomatoes, peppers or eggplant for the past several years. These crops share diseases.
2. Loosen the soil deeply and work in organic matter. Do not add lime unless a soil test calls for it: UGA notes scab can infect potatoes in soil of pH 5.5 to 7.0 (see below).
3. Open a furrow or trench. Montana State University Extension suggests a trench about 6 inches deep, covering the seed with about 4 inches of soil and filling the rest in as shoots emerge.
4. Set seed pieces cut side down, eyes up, 10–12 inches apart, with rows 24–36 inches apart (University of Illinois Extension). UMD notes closer spacing (about 9 inches) suits new potatoes, while spacing up to 20 inches gives larger storage potatoes.
5. Cover with soil. Recommended depths vary by state: 1–3 inches in Illinois, 2–3 inches in Nebraska, 3–5 inches in Maryland (5–6 inches for late crops) and 4–5 inches in Georgia. About 2–4 inches suits most gardens; go a little deeper in light soil or for late plantings.
6. Water if the soil is dry, but do not soak cold soil, which invites seed-piece rot. Nebraska Extension says shoots emerge one to three weeks after planting, depending on soil warmth.

Spacing and depth above follow Maryland, Illinois, Nebraska and Montana Extension guides; check your state's guide for local tweaks.

Hilling: why it matters and how to do it

New tubers form on underground stems (stolons) near the original seed piece. Hilling, drawing loose soil up around the stems, keeps them buried. Tubers exposed to light turn green; UMD notes green portions are associated with solanine, a bitter, toxic compound, and should be cut out.

1. Montana State University Extension recommends the first hilling when stems are about 8 inches high, drawing soil up from both sides; Nebraska Extension waits until plants are about a foot tall.
2. Montana State suggests hilling two more times at two-week intervals. Illinois describes a ridge that may reach 4 to 6 inches high by summer, and UMD advises keeping the tops of hills no more than 6 inches above grade.
3. Where hilling soil is short (raised beds, containers), straw works as a substitute. Illinois describes "straw potatoes": seed set at the soil surface under 4 to 6 inches of loose straw, which keeps soil about 10°F cooler and more uniform. Add more straw as it thins.

Watering, feeding and soil pH

• Water: Keep potatoes evenly moist but not soggy, especially while tubers are developing (Montana State University Extension; University of Maryland Extension). UMD links too much or too little water to tuber disorders such as blackheart, cracks and misshapen tubers, and Illinois notes uniform moisture prevents knobs from secondary growth. Avoid overhead watering, which UMD says can spread fungal disease. Montana State suggests reducing water in late summer before digging storage potatoes.
• Fertilizer: UMD notes potatoes have a high nutrient requirement: fertilize before planting and side-dress about 6 weeks later, when tubers begin to form. Montana State warns that manure often promotes scab.
• pH: UMD recommends pH 6.0 to 6.5, or 4.8 to 5.8 where potato scab is a persistent problem. UGA Extension puts the best range at 4.8 to 5.4, notes scab can infect potatoes at pH 5.5 to 7.0, and advises no lime unless a soil test shows pH below 4.8. If you need to adjust pH for other crops, see raising soil pH with lime and time it away from potato years.

Growing potatoes in containers, bags and buckets

UMD notes potatoes can be grown successfully in containers, though potato "towers" usually don't work. Use fabric grow bags, half-barrels, or large buckets with drainage holes. Bigger containers give bigger yields, because the plant can only make tubers in the soil it has.

1. Drill drainage holes if the container has none.
2. Add 4–6 inches of moist potting mix mixed with compost.
3. Set seed pieces on the mix, a few inches apart around the container (fewer pieces in smaller containers), and cover with 3–4 inches of mix.
4. As shoots grow, keep adding mix or straw until the container is nearly full, leaving the top few inches of foliage exposed each time.
5. Water whenever the top inch is dry; containers dry fast in summer.
6. Harvest by tipping the container out onto a tarp once the foliage dies back.

Comparing container and in-ground growing? See raised bed vs in-ground vegetable gardens.

How long potatoes take, and when to harvest

University of Maryland Extension lists 90 to 120 days to maturity, depending on cultivar and weather. You have two harvest options:

1. Wait for dry soil. UMD advises not digging when the soil is wet.
2. Dig gently around the plant with a garden fork, well away from the stems, then lift the plant and sift the soil by hand. UMD notes bruises and cuts let in organisms that cause storage rots.
3. Do not wash potatoes you plan to store. Gently knock off attached soil and set aside any that are cut or bruised to eat first.
4. Cure storage potatoes for 10–14 days at 50–60°F and high humidity (University of Maryland Extension), which heals over wounds and cuts.
5. Store cured potatoes in the dark, cool and humid: UMD gives 40–50°F at about 90% relative humidity for 6 to 8 months, and Illinois gives 38–40°F, warning that temperatures below 38°F cause internal damage. Do not refrigerate. Light turns them green.

For other crops' timing, the vegetable harvest calendar lists days to harvest side by side.

Pests and diseases to watch for

• Late blight (Phytophthora infestans) is favored by cool, wet weather and also attacks tomatoes. Penn State Extension describes pale green to brown leaf spots with water-soaked margins and, in moist conditions, downy white growth on leaf undersides; lesions can defoliate plants within 14 days, and tubers can be infected by spores splashing into the soil. Start with certified seed, avoid overhead watering and remove infected plants promptly (bag them; do not compost). Details: late blight on potatoes, and early vs late blight for telling the two apart.
• Colorado potato beetle adults (about ⅜ inch, with ten black stripes on yellow-white wing covers) and their larvae strip foliage fast. Illinois Extension notes the beetle is resistant to most home garden insecticides. Hand-pick adults, crush yellow-orange egg clusters under leaves, and use row cover early in the season; UMD adds that a thick straw mulch after hilling helps deter them. See Colorado potato beetle.
• Flea beetles and leafhoppers also feed on potato foliage; Illinois describes flea beetle holes and leafhopper "hopper burn" (browned leaf edges).
• Common scab causes rough, corky patches on the skin. Keep soil pH low (see above), avoid fresh manure, and keep moisture even while tubers form, which Montana State says reduces scab. Nebraska Extension suggests moving potatoes to a different part of the garden if scab has been a problem.

Common mistakes

Frequently asked

When should you plant potatoes?

Plant in early spring once the soil is at least 45°F, which in warm areas is usually before the last spring frost. That is roughly May in zones 3–4, March to early May in zones 5–6, and late winter in zones 8 and warmer. Potatoes tolerate light frost but not a hard freeze.

How deep do you plant potatoes?

Extension guides range from 1–3 inches of cover (Illinois) to 3–5 inches (Maryland), so about 2–4 inches suits most gardens. Space pieces 10–12 inches apart in rows 24–36 inches apart, and hill soil around the stems as plants grow.

How long do potatoes take to grow?

University of Maryland Extension lists 90 to 120 days to maturity, depending on the cultivar. New potatoes can be dug about 6–8 weeks after planting, usually once plants have flowered; storage potatoes are ready about 2 weeks after the vines die back.

How do you know when potatoes are ready to harvest?

For storage potatoes, wait until the vines have died back, then leave the tubers in the ground about 2 more weeks so the skins thicken. Dig on a dry day. For new potatoes, dig carefully around plants about 6–8 weeks after planting, once they have flowered.

Can you plant a regular potato from the store?

It may sprout, but extension services recommend certified seed potatoes instead. University of Maryland Extension notes supermarket potatoes can carry diseases without showing symptoms, so they can bring problems into your garden and may perform poorly.

Do you cut seed potatoes before planting?

Cut large seed potatoes into pieces of about 1½ to 2 ounces with at least one good eye each, and let them dry for a day or two so the cuts heal before planting. Plant small seed potatoes whole.

Can you grow potatoes in a container?

Yes. Use a large grow bag, barrel or bucket with drainage holes, start with a few inches of potting mix, plant seed pieces, and keep adding mix or straw as plants grow. Water often, since containers dry out quickly.

Sources

1. Tomato-Potato Late Blight in the Home Garden, Penn State Extension
2. Growing Potatoes in a Home Garden, University of Maryland Extension
3. Potato, University of Illinois Extension
4. Planting Seed Potatoes, Nebraska Extension in Lancaster County
5. Potato Growing Guide, Montana State University Extension
6. How do I plant my potatoes?, UGA Cooperative Extension, Colquitt County

Read next