Gardening glossary
Cloche
The original cloche was a bell-shaped glass dome used in 19th-century French market gardens around Paris (the word literally means "bell"). The technique was so effective that the Parisian market garden tradition could supply lettuce, melons, and asparagus to the city year-round on tiny acreages. Modern cloches keep the principle but use cheaper materials.
Cloche types you will see today:
- **Glass bell jars** — beautiful, expensive, heavy, and prone to overheating on sunny days. Mostly decorative now. - **Plastic dome cloches** — clear or translucent rigid plastic, 30–50 cm diameter. Affordable and easy to vent. - **Plastic tunnels (mini polytunnels)** — wire hoops covered in clear plastic film, running along a row. Handle 3–10 plants at a time. - **DIY bottle cloches** — the bottom cut off a 2-litre plastic bottle, lid removed for ventilation, pushed firmly into the soil over a seedling. Free and surprisingly effective.
What cloches do for the plant:
1. **Warm the air immediately around the plant by 3–8 °C** during the day. The greenhouse effect is real even in a 5-litre bottle. 2. **Protect from late spring frost.** A cloche provides roughly 2–4 °C of frost protection on a still night. 3. **Block slugs and snails** — they cannot easily climb glass or plastic walls. 4. **Reduce wind chill** on tender transplants. Even a windbreak with the top open helps. 5. **Speed germination** of direct-sown seed. Sow lettuce, carrots, or radish under a cloche in March and they emerge 7–10 days earlier than uncovered rows.
Practical rules:
- **Ventilate or overheat.** Without an opening, internal temperatures on a sunny April day can hit 35 °C even when the air outside is 8 °C — enough to cook seedlings. Either remove the cap, prop the cloche open, or lift it off completely during the warmest hours. - **Lift for watering.** Water reaches a cloched plant poorly. Lift the cloche, water around the base, and replace. - **Remove before flowering.** Pollinating insects need access; cloches that worked for an early-spring seedling must come off by the time the plant flowers. - **Anchor in wind.** Stake or weigh dome cloches and bottle cloches — a strong gust will turn them into projectiles.
A few dozen cut plastic bottles plus a string of poly-tunnel cloches is enough to extend a vegetable garden's season by a full month at both ends, on a budget under £20.