🥔 Chitting Potatoes in Polytunnels

🌱 Introduction: A Great Option—With One Big Caveat

Polytunnels can be an excellent place to chit potatoes because they offer strong natural light and shelter from wind and rain. However, they also warm up quickly, and too much heat is the main risk. Used correctly, a polytunnel produces short, sturdy chits. Used incorrectly, it creates long, weak shoots.

This guide explains when chitting in a polytunnel works best, how to manage temperature, and what UK growers should watch out for.

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✅ When a Polytunnel Is a Good Place to Chit

Chitting in a polytunnel works well if you can provide:

• Bright daylight
• Cool temperatures
• Good ventilation
• Frost protection

Unheated polytunnels are usually best, as long as you control temperature swings.

🌡️ Temperature: The Make-or-Break Factor

Ideal temperature range:

👉 5–10°C

What to avoid:

• Daytime temperatures above 12–15°C
• Closed tunnels on sunny days
• Sudden heat spikes

Polytunnels can jump from cold to very warm in minutes. Ventilation is essential.

🌬️ Ventilation Is Non-Negotiable

To keep chits strong:

• Open doors or vents on mild, bright days
• Close up again before temperatures drop
• Avoid trapping warm air around potatoes

Stagnant, warm air leads to fast but weak growth.

❄️ Frost Protection in Polytunnels

Polytunnels do not guarantee frost protection.

During cold spells:

• Keep potatoes off the ground
• Move trays toward the centre of the tunnel
• Use fleece on cold nights
• Bring potatoes indoors during hard frosts

Freezing damages both tubers and chits.

📅 Best Time to Chit in a Polytunnel (UK)

Polytunnels are most suitable for chitting from:

• Mid-February onwards in most areas

Earlier than this, frost risk and temperature swings are harder to manage.

📦 Best Setup Inside a Polytunnel

• Use egg boxes, seed trays, or shallow boxes
• Place potatoes rose end up
• Space so shoots don’t touch
• Raise trays onto benches or shelves
• Keep away from tunnel edges and cold ground

Do not water or cover potatoes.

🌱 What Good Polytunnel-Chitted Potatoes Look Like

By planting time, aim for:

• 1–3 cm long shoots
• Thick, firm growth
• Green or purple colouring
• Usually 1–3 strong shoots per potato

These handle planting and cooler soil far better than long sprouts.

🚫 Common Polytunnel Chitting Mistakes

• ❌ Leaving tunnels closed on sunny days
• ❌ Starting too early “because it’s protected”
• ❌ Assuming polytunnels are frost-free
• ❌ Chitting on the ground or near cold edges

Most problems come from overheating, not cold.

🌱 Is a Polytunnel Better Than Indoors?

A polytunnel can be better if:

• You can ventilate daily
• Frost protection is reliable
• Temperatures stay cool

Indoors is better if:

• You can’t control tunnel heat
• Frosts are frequent
• You’re away and can’t open/close daily

Choose the most stable environment, not just the brightest.

🧠 Key Takeaway

Chitting potatoes in a polytunnel works very well when temperature is controlled. Bright light is a big advantage, but overheating and frost are real risks. Keep conditions cool, ventilated, and frost-free, and your polytunnel will produce strong, planting-ready chits.

Remember:
Light helps. Heat harms. Control is everything.