How to Plant Potatoes in Polytunnels

Planting potatoes in a polytunnel is a great way to get earlier harvests, better protection from bad weather, and more reliable crops in the UK. Polytunnels warm the soil sooner in spring and extend the growing season, making them ideal for early potatoes and controlled growing.

⭐ Recommended Products — Seed Potatoes & Planting Essentials

• Seed Potato Collection (Early, First & Second Earlies)
A mixed pack of quality seed potatoes to plant for a steady harvest from early summer through to autumn. Ideal if you want variety in size and maturity times.
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• Certified Seed Potatoes (Single Variety Packs)
Choose popular individual varieties (e.g., Maris Piper, Charlotte, King Edward) to suit your taste and growing goals — consistent results from true seed stock.
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• Potato Grow Bags / Containers
Reusable, breathable bags designed specifically for growing potatoes — great for patios, small gardens, or increasing yield in limited space.
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• Potato Fertiliser / Soil Booster
Specially formulated feed to support healthy tuber development and improve yields — apply at planting or as a top-dress during the season.
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• Potato Planting Guides & Markers
Helpful tools and guides that take you through planting depth, spacing, and care — plus reusable markers to keep track of different varieties.
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Why Grow Potatoes in a Polytunnel?

Growing potatoes under cover offers several advantages:

• Soil warms earlier for faster growth
• Earlier planting and harvesting
• Protection from heavy rain and late frosts
• Reduced blight risk due to drier foliage
• More control over watering

Polytunnels are especially useful in colder or wetter areas.

Best Potatoes to Grow in a Polytunnel

Polytunnels are best suited to:

• First early potatoes
• Second early potatoes
• Salad varieties

Maincrop potatoes can be grown, but they take up a lot of space and are usually better grown outdoors.

When to Plant Potatoes in a Polytunnel

In the UK, you can plant potatoes in a polytunnel:

• Late January to February (first earlies)
• February to early March (second earlies)

This is often 4–6 weeks earlier than outdoor planting, depending on weather and tunnel conditions.

Step 1: Prepare the Polytunnel Bed or Containers

Potatoes can be grown in:

• Polytunnel beds
• Raised beds
• Containers, grow bags, or buckets

Ensure soil or compost is:

• Free-draining
• Loose and fertile
• Enriched with well-rotted compost

Avoid fresh manure, which can cause scab.

Step 2: Chit Seed Potatoes

Chitting is strongly recommended for polytunnel growing:

• Start chitting 4–6 weeks before planting
• Aim for short, sturdy shoots (1–2 cm)

Chitted potatoes take full advantage of warmer tunnel conditions.

Step 3: Plant at the Correct Depth

• Plant seed potatoes 10–15 cm deep
• Shoots (chits) facing upwards

This depth works for beds, raised beds, and containers.

Step 4: Space the Potatoes Correctly

Spacing depends on the type:

• First earlies: 30 cm apart
• Second earlies: 30 cm apart
• Maincrop (if grown): 35–40 cm apart

Leave enough room for airflow and earthing up.

Step 5: Water Lightly After Planting

• Water gently if soil or compost is dry
• Do not overwater
• Cold, wet soil can cause seed potatoes to rot

Polytunnel soil stays drier than outdoor beds.

Step 6: Protect Against Frost

Even inside a polytunnel, frost is possible.

• Cover beds with fleece on cold nights
• Earth up shoots early if frost is forecast
• Close doors and vents in cold weather

Young shoots are very frost-sensitive.

Step 7: Earth Up as Plants Grow

Earthing up is essential:

• When shoots reach 10–15 cm, draw soil or compost around stems
• Leave top leaves exposed
• Continue until ridges reach about 20 cm high

This prevents greening and increases yields.

Step 8: Ventilation and Temperature Control

As temperatures rise:

• Open doors and vents on warm days
• Avoid overheating, which stresses plants
• Good airflow reduces disease risk

Ideal daytime temperatures are cool to mild rather than hot.

Step 9: Watering and Feeding

• Water regularly but lightly
• Avoid waterlogging
• Water most during flowering and tuber formation

Feed lightly once flowering begins using a balanced fertiliser.

Step 10: Harvesting Potatoes in a Polytunnel

• First earlies: Harvest when flowering begins
• Second earlies: Harvest just after flowering

Polytunnel potatoes are often ready weeks earlier than outdoor crops.

To harvest:

• Gently lift with a fork
• Or tip containers and collect by hand

Common Mistakes to Avoid

• Planting too early without frost protection
• Overwatering in cool conditions
• Poor ventilation in warm weather
• Growing too many maincrop potatoes under cover

How Early Can You Harvest?

With good conditions:

• New potatoes can be ready as early as April or May
• This is several weeks ahead of outdoor crops

Quick Summary

• Plant 4–6 weeks earlier than outdoors
• Use first or second early varieties
• Plant 10–15 cm deep
• Space 30–40 cm apart
• Earth up regularly
• Ventilate on warm days

Final Tip

Polytunnels are perfect for producing early, high-quality potatoes. Focus on early varieties, protect against frost, and manage temperature carefully for the best results.