Interactive lesson

The tunnel through the year, step by step

Interactive lesson: three seasons in the same polytunnel — what to plant and at what spacing, single-stem tomatoes, cucumbers, peppers and aubergines, winter greens and looking after the soil.

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The whole lesson as text

1. Three seasons

The same unheated tunnel can crop from March to March.

Spring greens — February–April in lowland UK and Ireland: lettuce, radish, spinach, spring onions and seedlings for the garden. Sown into cold soil, with fleece at night.
Summer warm crops — May–October: tomatoes, peppers, cucumbers, aubergines and basil. Planted when the soil passes 12–14 °C (54–57 °F).
Autumn and winter greens — September–March: lamb's lettuce, spinach, winter lettuce, rocket, chard, kale and spring onions. Sown in August and September, picked all winter.
The 10-hour rule — From early November to early February the day in the UK and Ireland is shorter than 10 hours and greens hardly grow. Winter plants must be almost full-grown by early November.

Why: Most polytunnels work for half the year: tomatoes from May to October, and from November to April the tunnel stands empty. The same tunnel can give early lettuce and radishes in spring, warm crops in summer and greens in winter.

There is no idle time between seasons: spring lettuce is picked while the tomatoes are planted between it.
If you sow winter greens in November, you won't pick them until March.

2. What goes where

The tunnel is for crops whose yield warmth and shelter increase most.

Main crops — Tomatoes and cucumbers give 10 kg/m², peppers and aubergines 6 kg/m². Outdoors tomatoes give 4 and cucumbers 3 kg/m².
Tall ones in the middle — Tomatoes and cucumbers go in the middle or on the north side, so they don't shade lower crops. Peppers and aubergines go on the south side or along the edges.
Planting distances — Tall (cordon) tomatoes in 2 rows 60–70 cm apart, 45–50 cm in the row. Peppers 40 × 40 cm, cucumbers in 2 rows, 40–50 cm in the row.
Strings and neighbours — From a wire at 2–2.2 m, drop a string to each tomato and cucumber plant. Plant basil between the tomatoes and French marigolds along the edges.

Why: Tomatoes and cucumbers give 10 kg/m² in a tunnel, and 4 and 3 kg/m² outdoors. Plants grow more lushly inside: planting too close means damp air, mould and fewer fruits, not more.

Not for the tunnel: potatoes, sweetcorn, squash and courgettes, runner and French beans, cabbage for storage. They take up a lot of space and crop well enough outdoors.
In the cool summers of the uplands and Scotland, a tunnel is the only way to have tomatoes, peppers, cucumbers and aubergines.