🍆 Sowing Aubergine Seeds in Polytunnels

Polytunnels offer a warmer, more controlled environment than outdoor growing, making them an excellent choice for aubergines in the UK. However, timing and temperature still matter — especially at the seed-sowing stage.

This guide explains how and when to sow aubergine seeds for polytunnel growing, and how to avoid common problems.

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• Aubergine Seeds

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• Seed Compost

Fine, low-nutrient seed compost provides the right balance of moisture and drainage, helping aubergine seeds germinate evenly without rotting.
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• Propagators

A propagator helps maintain consistent warmth and humidity, which is crucial for aubergine seed germination, particularly in late winter and early spring.
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• Seed Trays & Module Pots

Using seed trays or module pots keeps seedlings organised, improves drainage, and makes potting on easier with minimal root disturbance.

📅 Best Time to Sow Aubergine Seeds for Polytunnels

Even when growing in a polytunnel, aubergine seeds should usually be started indoors.

• Mid-February to early March is ideal
• Avoid January sowing unless your polytunnel is heated
• Late March is possible but reduces growing time

Early indoor sowing gives plants a strong start before moving into the tunnel.

🌡️ Are Polytunnels Warm Enough for Germination?

Most unheated polytunnels are too cold for germination in late winter.

Aubergine seeds need:

• 22–28°C compost temperature

Polytunnels often drop well below this at night, even on sunny days.

🌱 Best Sowing Method for Polytunnel Crops

For reliable results:

• Sow seeds indoors in small pots or modules
• Use fine seed compost
• Sow 1–2 seeds per pot, 3–5mm deep
• Keep compost warm and evenly moist

Once seedlings are established, they can be moved to the polytunnel later.

🌞 Moving Seedlings Into the Polytunnel

Transfer plants to the polytunnel when:

• Night temperatures stay above 12–14°C
• Plants are strong and well rooted
• Frost risk has passed

In many UK areas, this is late April to May.

🌿 Advantages of Polytunnel Growing

Polytunnels provide:

• Higher daytime temperatures
• Protection from wind and rain
• Longer growing season
• Better fruit ripening

These conditions are ideal for aubergines once established.

🚫 Common Mistakes in Polytunnels

• Sowing seeds directly in the polytunnel too early
• Underestimating night-time cold
• Poor ventilation on warm days
• Overwatering in cooler conditions

Ventilation and temperature control are just as important as warmth.

🌡️ Managing Heat and Ventilation

• Vent polytunnels on warm days
• Close them early in the evening to retain heat
• Avoid sudden temperature swings

Balanced conditions reduce plant stress.

🧠 Key Takeaway

Polytunnels are excellent for growing aubergines — but not ideal for early seed sowing unless heated. Start seeds indoors in mid-February to early March, then move plants into the polytunnel once temperatures are reliably warm.

Strong starts lead to better tunnel harvests.