Purple potatoes are grown the same way as other potatoes, but their deep violet flesh makes them a standout in the garden and in the kitchen. Most gardeners don’t plant “seeds” in the usual sense. Instead, they plant small tubers called seed potatoes (or pieces of a potato) that sprout from the “eyes.”
Key takeaways
- Plant certified purple seed potatoes (tubers), not botanical seeds, for reliable results.
- Aim for loose, well-drained soil and the pH range recommended for potatoes (adjust if scab is a problem).
- Plant 4–6 inches deep, 10–12 inches apart, then “hill” soil around stems as plants grow.
- Keep moisture consistent (about 1–2 inches of water per week), especially when tubers are forming.
- Harvest when vines yellow and die back; cure and store in a cool, dark, well-ventilated place.
What “purple potato seeds” really are
Potatoes are Solanum tuberosum cultivars. Purple-fleshed types (often called blue or purple potatoes) include popular options such as ‘Purple Majesty’ and ‘Adirondack Blue.’ When people say “purple potato seeds,” they usually mean seed potatoes: small tubers grown for planting.
Potato plants can also produce small green fruits (“potato berries”) that contain true botanical seeds. Growing from true potato seed is mostly used for breeding because seedlings don’t grow true-to-type. The berries (and other green parts of the plant) are not edible.
The purple color comes largely from anthocyanins, a group of pigments that act as antioxidants. Research on anthocyanin-rich foods suggests potential anti-inflammatory and cardiovascular benefits, but these findings don’t mean purple potatoes prevent or cure disease.
Selecting the right growing conditions
Soil: Choose loose, fertile, well-drained soil. Potatoes grow best in well-drained soil high in organic matter with a pH around 6.0–6.5. If common scab is a persistent problem, a slightly more acidic pH (roughly 4.8–5.8) is often recommended. A soil test helps you adjust pH and nutrients before planting.
Temperature and timing: Potatoes are a cool-season crop. Plant when the soil is workable and at least 45°F (about 7°C). In many climates, that’s about 2–3 weeks before the average last spring frost date.
Sun: Full sun is best—aim for at least 6 hours of direct light per day.
Preparing the soil for planting
Clear weeds and debris, then loosen the soil 8–12 inches deep. Mix in organic matter such as compost or well-rotted manure to improve structure and drainage. Raised beds or mounded rows can help in heavy soils.
If you need compost guidance, see the RHS compost guide.
Planting purple seed potatoes
See the USU Extension potato guide for a clear step-by-step overview.
Start with certified, disease-free seed potatoes. If your seed potatoes are large, cut them into pieces about 1½–2 ounces (roughly 40–60 g), making sure each piece has at least one eye. Let cut pieces dry for 1–2 days so the cut surface can callus over.
Plant pieces 4–6 inches (10–15 cm) deep with the eyes facing up. Space plants 10–12 inches (25–30 cm) apart, with rows 30–36 inches (75–90 cm) apart.
Hill as you grow: When shoots are 6–8 inches tall, mound a few inches of soil around the stems, leaving the top leaves exposed. Repeat as needed. Hilling keeps tubers covered (preventing greening) and gives them room to expand.
Watering and fertilizing
Provide steady moisture—about 1–2 inches of water per week from rain and irrigation combined. Avoid soggy soil, which can encourage rot and disease, but don’t let plants dry out during tuber set and bulking.
Before planting, mix in compost and (if your soil test calls for it) a balanced fertilizer. Avoid heavy nitrogen later in the season; too much can produce lush leaves with fewer tubers. If plants look pale or growth stalls, side-dress lightly and water it in.
Managing pests and diseases
Common pests include aphids and Colorado potato beetles. Scout plants weekly, hand-pick beetles when numbers are low, and use row covers early in the season if needed. Rotate crops so potatoes (and other nightshades like tomatoes and peppers) don’t grow in the same spot year after year.
For diseases, focus on prevention: start with clean seed potatoes, keep plants well spaced for airflow, and avoid wet foliage when possible. Late blight favors cool, wet weather. Common scab is more likely when soils are dry during early tuber development and when soil pH is higher; consistent moisture and appropriate pH help reduce risk.
Monitoring growth and development
Healthy plants have strong green growth. Yellowing may signal nutrient issues or uneven watering. Flowering often coincides with early tuber formation, so keep moisture consistent and avoid over-fertilizing at that stage.
Harvesting purple potatoes
“New” potatoes can be harvested carefully about 6–8 weeks after planting, usually once plants have flowered. For main-crop harvest, wait until vines yellow and die back. For potatoes you plan to store, many guides recommend leaving tubers in the ground for about 1–2 weeks after dieback so skins can set, then digging on a dry day.
Storing purple potatoes
Handle tubers gently and brush off loose soil—don’t wash before storage. Cure potatoes in a dark place with good airflow for 10–14 days at roughly 50–60°F (10–16°C). Then store them in the dark, ideally around 40–50°F (4–10°C) with ventilation. Check periodically and remove any tubers that soften or show decay.
Tips for success
- Use crop rotation (3–4 years between potato crops in the same bed) to reduce disease pressure.
- Mulch after emergence to help hold moisture and reduce weeds.
- Keep developing tubers covered with soil or mulch to prevent green, bitter potatoes.
Troubleshooting common issues
Lots of leaves but few potatoes: too much nitrogen, too much shade, or hot weather (soil temperatures above about 80°F/27°C) can slow tuber development. Adjust fertilizer, increase sun exposure, and plant earlier next season if heat arrives quickly in your area.
Scabby tubers: maintain steadier soil moisture during early tuber development and keep pH in the recommended range for potatoes. Start with clean seed and rotate crops.
Rotting seed pieces: plant into well-drained soil, avoid overwatering early, and let cut seed pieces callus before planting.
FAQs
What are purple potato “seeds”?
In home gardening, “seeds” usually means seed potatoes—small tubers (or cut pieces) that sprout from the eyes. Potatoes can also be grown from true botanical seed found in potato berries, but that’s mainly for breeding and experimentation.
When should I plant purple seed potatoes?
Plant when the soil is workable and at least 45°F (about 7°C). In many climates this is a few weeks before the average last spring frost.
How deep should I plant seed potatoes?
Most home-garden guides recommend planting 4–6 inches (10–15 cm) deep, then hilling soil up around the stems as plants grow.
How long does it take for seed potatoes to sprout?
Sprouting speed depends on soil temperature and moisture. In cool spring soil, it often takes a few weeks for shoots to break the surface.
Are potato berries or true potato seeds edible?
No. Potato berries and other green parts of the plant contain natural toxins (glycoalkaloids such as solanine) and shouldn’t be eaten.
How long do purple potatoes take to mature?
Many home-garden potatoes are listed at roughly 90–120 days to maturity, but weather and variety can shift timing. Use the days-to-maturity information for your specific cultivar as your guide.
