Seed Potatoes: When to Plant for a Successful Harvest

Knowing when to plant seed potatoes is essential for a healthy and productive potato crop. Seed potatoes, which are certified disease-free tubers, must be planted at the right time to ensure they grow well and produce a bountiful harvest. The ideal planting time varies depending on the type of seed potato, your local climate, and soil conditions.

This guide provides all the information you need to determine the best time to plant seed potatoes, along with tips for preparation, planting, and care.

Factors That Influence When to Plant Seed Potatoes

1. Type of Seed Potato:
   • Different types (first earlies, second earlies, and maincrop) have specific planting and harvesting times.
2. Soil Temperature:
   • Seed potatoes should be planted in soil that has warmed to at least 7°C (45°F).
   • Cold, wet soil can delay sprouting or cause rot.
3. Climate and Frost Risk:
   • Potatoes are frost-sensitive, so avoid planting too early when frost is still likely.
   • Use cloches or fleece for protection if planting early.
4. Growing Method:
   • Potatoes grown in containers or bags can often be planted earlier, as the soil warms up faster.

When to Plant Seed Potatoes

1. First Early Seed Potatoes

• Planting Time: Late February to early March.
• Harvest Time: 10–12 weeks after planting.
• Best For: Tender new potatoes.
• Examples: Rocket, Swift, Arran Pilot.

2. Second Early Seed Potatoes

• Planting Time: Mid-to-late March.
• Harvest Time: 13–15 weeks after planting.
• Best For: Salads and mid-season meals.
• Examples: Charlotte, Kestrel, Maris Peer.

3. Maincrop Seed Potatoes

• Planting Time: Late March to early April.
• Harvest Time: 18–20 weeks after planting.
• Best For: Large yields and long-term storage.
• Examples: Maris Piper, King Edward, Desiree.

Regional Planting Times for Seed Potatoes in the UK

• Southern England and Coastal Areas:
  • Plant as early as late February due to milder winters.
• Northern England and Scotland:
  • Wait until mid-to-late March or early April to avoid frost damage.
• Cooler Areas or Higher Altitudes:
  • Plant in early April to ensure frost-free conditions.

Preparing to Plant Seed Potatoes

1. Chitting Seed Potatoes

Chitting encourages sprouting and ensures faster growth once planted.

• Start chitting 4–6 weeks before planting (typically in January or February).
• Place seed potatoes in a cool, bright spot with the eyes (sprouting points) facing upward.
• Allow sprouts to grow to 2–3 cm before planting.

2. Preparing the Soil

• Choose a sunny location with well-drained, fertile soil.
• Add compost or well-rotted manure to enrich the soil.
• Ensure the soil pH is between 5.5 and 6.5 for optimal growth.

How to Plant Seed Potatoes

1. Planting in the Ground

1. Dig trenches or holes about 10 cm deep.
2. Place chitted seed potatoes with the sprouted eyes facing upward.
3. Space seed potatoes:
   • First and second earlies: 30 cm apart with rows 60 cm apart.
   • Maincrop potatoes: 40 cm apart with rows 75 cm apart.
4. Cover with soil and water thoroughly.

2. Planting in Containers or Bags

1. Fill the container or potato bag with 10 cm of soil or compost.
2. Place 3–5 seed potatoes evenly spaced on the surface.
3. Cover with another 10 cm of soil and water lightly.
4. Add more soil as the plants grow, leaving the top leaves exposed.

Caring for Planted Seed Potatoes

1. Watering

• Keep the soil consistently moist, especially during dry spells.
• Avoid overwatering to prevent tuber rot.

2. Earthing Up

• As the plants grow, mound soil or compost around the stems to protect developing tubers from sunlight and prevent greening.

3. Frost Protection

• Cover young plants with fleece or cloches if frost is forecast.

4. Pest and Disease Management

• Rotate crops annually to reduce the risk of blight and other diseases.
• Protect against pests like slugs, wireworms, and aphids using organic methods.

What Happens If You Plant Seed Potatoes Too Early or Too Late?

Planting Too Early:

• Frost damage can kill young plants.
• Cold, wet soil can delay sprouting or cause the seed potatoes to rot.

Planting Too Late:

• Shortened growing season may reduce yields.
• Tubers may not mature fully before the first frost in autumn.

Top Tips for Planting Seed Potatoes

1. Monitor Soil Temperature:
   • Use a soil thermometer to ensure the soil is at least 7°C (45°F) before planting.
2. Protect Early Plantings:
   • Use cloches or fleece to protect young plants from frost.
3. Choose the Right Variety:
   • Match the potato variety to your desired harvest time and intended use.
4. Rotate Crops:
   • Avoid planting potatoes in the same spot each year to prevent soil-borne diseases.
5. Enrich Your Soil:
   • Add compost or manure to provide nutrients for healthy growth.

Top 10 Questions About When to Plant Seed Potatoes

1. When should I plant seed potatoes in the UK?

• Plant first earlies in late February to early March, second earlies in mid-to-late March, and maincrop potatoes in late March to early April.

2. Can I plant seed potatoes too early?

• Yes, planting too early can expose young plants to frost and cold, wet soil, which may delay sprouting or cause rot.

3. How do I protect seed potatoes from frost?

• Use fleece, cloches, or a layer of soil to shield young plants from frost.

4. What temperature should the soil be for planting seed potatoes?

• The soil should be at least 7°C (45°F) for planting.

5. When should I start chitting seed potatoes?

• Start chitting 4–6 weeks before planting, typically in January or February.

6. Can I plant seed potatoes in containers earlier than in the ground?

• Yes, containers warm up faster, so you can plant earlier if frost protection is provided.

7. What happens if I plant seed potatoes too late?

• Late planting can reduce yields or result in immature tubers before the first frost.

8. Can I grow potatoes all year round?

• In the UK, potatoes are typically planted in spring, but late-season varieties can be planted in summer for an autumn or winter harvest.

9. Should I use supermarket potatoes as seed potatoes?

• It’s not recommended, as they may carry diseases and are often treated to prevent sprouting.

10. How do I know when to harvest seed potatoes?

• First and second earlies are ready 10–15 weeks after planting when plants flower, and maincrop potatoes are ready 18–20 weeks after planting when foliage dies back.

Conclusion

Knowing when to plant seed potatoes is key to achieving a healthy and productive harvest. By considering the type of potato, local climate, and soil conditions, you can ensure your potatoes thrive. Whether you’re planting in a garden bed, container, or potato bag, timing your planting correctly will set you up for a delicious and abundant crop.