What to plant
Growing Potatoes in Raised Beds
Plant certified seed potatoes 2–3 weeks before your last spring frost, about 4 in deep and 12 in apart, in a bed with 12–18 in of loose soil and full sun. Hill soil around the stems as they grow.
| Early varieties | Main-crop varieties | |
|---|---|---|
| Plant | 2–4 weeks before last frost | 2–3 weeks before last frost |
| Spacing | 10–12 in | 12 in |
| Planting depth | 4 in | 4 in |
| Days to harvest | About 70–90 | About 100–130 |
| Plants in a 4x8 bed | About 32 | About 24–32 |
| Best use | Eating fresh as "new" potatoes | Storing through winter |
When to plant
Potatoes are a cool-season crop. Plant seed potatoes about 2–3 weeks before your average last spring frost, once the soil has warmed to at least 45°F and isn't soggy. Raised beds are often ready first.
Shoots usually take 2–3 weeks to come up. If a late frost is forecast after they emerge, pull a few inches of soil or straw over them or cover the bed with frost cloth overnight.
In mild-winter areas, potatoes can also go in during late summer or early fall for a crop before cold weather.
Spacing and depth
Space seed pieces about 12 in apart in every direction. Early varieties can go 10 in apart. Closer spacing gives more, smaller potatoes.
Potatoes form along the buried stem, above the seed piece, so soil depth matters. A bed with 12 in of loose soil is the minimum; 18 in gives you room to plant and hill without running out. Our bed depth guide covers deep-rooted crops in more detail.
Set seed pieces in holes about 4 in deep, cut side down, and cover them.
Soil and feeding
Potatoes want loose, slightly acidic soil, ideally pH 5.5–6.5. Above about 6.5, common scab (rough, corky patches on the skin) becomes more likely, so don't add lime unless a soil test calls for it.
A standard raised bed blend works well: mostly screened topsoil with about a third compost and some pine bark fines or perlite. See the raised garden bed soil mix guide for how to mix it. Avoid fresh manure, which can encourage scab; use well-finished compost instead.
At planting, work in a balanced fertilizer at the label rate. Too much nitrogen gives big leafy tops and fewer tubers. A light side-dressing of compost at the first hilling is usually all they need after that.
Don't plant potatoes where potatoes, tomatoes, peppers or eggplant grew in the last two or three years. They share blights and soil-borne diseases.
Watering
Potatoes need steady moisture, about 1–2 in a week, most of all from flowering onward, when tubers are sizing up. Uneven watering causes knobby, cracked or hollow potatoes.
Check the soil 2 in down every couple of days and water deeply when it's dry. Water at the soil line rather than over the leaves to keep blight at bay. A 2–3 in layer of straw after the final hilling holds moisture and keeps tubers covered.
Once the foliage starts to yellow and die back, cut back on water.
Seed potatoes, hilling and harvest timing
Seed potatoes. Buy certified disease-free seed potatoes from a garden supplier. Grocery store potatoes may carry disease and are often treated to slow sprouting. Small seed potatoes about the size of an egg can go in whole. Cut larger ones into pieces of about 1½–2 oz with at least one or two eyes each, then let the cut surfaces dry for a day or two before planting.
Hilling. When shoots are 6–8 in tall, pull soil, compost or straw up around the stems so only the top few inches of leaves show. Repeat every 2–3 weeks until the plants flower or the hill is about 12 in above the original planting depth. Potatoes that see light turn green and develop solanine, which is bitter and can make you ill, so cut away any green parts or discard badly greened potatoes.
Depth for hilling. In a raised bed, either plant low and fill the bed as you hill, or leave the bed 4–6 in short of full when you plant so there's room to add soil later.
Harvest timing. For new potatoes, dig gently around the edges 2–3 weeks after the plants flower. For storage potatoes, wait until the vines have died back completely, then leave the tubers in the ground another 2 weeks so the skins toughen.
Harvest
Dig on a dry day. Start at the edge of the bed and loosen the soil with a garden fork, working inward, to avoid spearing tubers. In loose bed soil you can often pull many out by hand.
Brush off soil but don't wash potatoes you plan to store. Cure them in a dark, humid spot at about 50–60°F for 1–2 weeks so small nicks heal. Then store them in the dark at about 40°F.
Once the bed is clear, add 1–2 in of compost and plant a fall crop of lettuce, spinach or garlic, or sow a cover crop for winter.
Common problems
Green skins
Tubers exposed to light turn green and bitter. Hill higher and mulch with straw.
Common scab
Rough, corky spots on the skin. Keep pH below about 6.5, skip fresh manure and keep soil evenly moist.
Colorado potato beetles
Striped beetles and their reddish larvae strip leaves. Hand-pick them and check leaf undersides for orange eggs.
Late blight
Dark, spreading patches on leaves in cool, wet weather. Remove infected plants promptly and don't compost them.
Knobby or hollow tubers
Caused by uneven moisture. Water deeply and regularly through flowering and tuber growth.
Lots of leaves, few potatoes
A sign of heavy feeding or shade. Use less fertilizer and give the bed more light next year.