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Cloche tunnels are low, continuous protective structures designed to shield plants from harsh weather, pre-warm the soil, and accelerate growth. Unlike individual bell cloches, tunnel versions provide a consistent environment over an entire row of crops. They function as miniature greenhouses, trapping solar heat to raise soil temperatures and protecting young seedlings from wind, hail, and heavy rain.
Table of Contents
Selecting the right hoops for tunnel cloches
The structure of a cloche tunnel relies on hoops that provide the necessary height and shape to support the cover. The choice of material depends on the span of the bed and the desired permanence of the structure.
- Wire hoops: These can be purchased ready-made or fashioned from thick gauge wire. They are suitable for narrow beds and lightweight covers.
- Bendable plastic pipe: PVC or similar flexible piping provides a sturdier frame for medium-width beds.
- Agricultural irrigation hose: Stiff irrigation pipe can be used for home-made hoops if it holds the intended curve and can be anchored securely; a pressure rating does not establish wind resistance.
- Metal tubing: For wider spans, choose a purpose-designed hoop system rated for the width and cover weight; material alone does not determine strength.
When installing hoops, ensure they are securely anchored into the soil. Because cloches are lightweight, they are prone to blowing away if the underlying frame is not stable.
Choosing covers for different goals
The material used to cover the hoops determines the tunnel’s internal climate, its level of insulation, and its effectiveness against pests.
Transparent plastic and polythene
Clear polythene is highly effective at trapping heat, making it ideal for pre-warming soil in early spring. However, unpierced plastic can lead to overheating and excessive humidity. Perforated or ‘aerated’ polythene allows some heat and moisture to escape, reducing the risk of crop damage on sunny days.
Horticultural fleece
Fleece is a soft, translucent material that provides good insulation and is less prone to overheating than plastic. It is particularly useful for protecting tender plants from frost, with heavier grades providing approximately 2°C of protection. Fleece is porous, but it can still raise temperature and humidity. Check crops beneath it and allow pollinator access where needed.
Specialist meshes and opaque covers
Insect-proof mesh can be used over hoops to create a physical barrier against pests without significantly raising the temperature. Opaque covers are for specific blanching or soil-covering jobs, not normal growth of leafy crops.
Managing access for watering and maintenance
One of the primary challenges of a continuous tunnel is accessing the plants for essential care. Solid polythene excludes most rain; fleece and mesh admit some water, but do not assume rainfall reaches the roots evenly.
Watering methods
Check soil moisture beneath the cover rather than relying on water at the edges. During dry weather, a low-level drip or seep irrigation pipe installed inside the tunnel is a highly effective way to ensure consistent moisture without lifting the cover.
Weeding and ventilation
The same conditions that benefit crops also encourage weed growth. To manage this, choose covers that can be easily removed and replaced. A practical approach is to create a ‘stale seedbed’ by covering the soil at least one week before sowing; once weed seedlings germinate, they can be removed with shallow hoeing before the crops are sown.
Airflow and pollination
Poor ventilation can lead to high humidity, encouraging diseases such as Botrytis and downy mildew. Lifting the sides of the tunnel or opening vents is essential. This is especially critical for insect-pollinated crops like strawberries and courgettes, which require access for pollinators to ensure successful fruit set.
Hardening off and seasonal transitions
Plants grown under the protected environment of a cloche tunnel produce ‘softer’, more lush growth because they are shielded from wind. If these plants are suddenly exposed to the elements, they may wilt or suffer damage.
To transition plants safely, a process of hardening off is required:
- Initial ventilation: Lift the lids or sides of the tunnel for a week to gradually introduce outdoor air.
- Gradual exposure: For rigid plastic or glass covers, remove them for a few hours each morning for one week before full exposure.
- Monitoring: Observe the plants for signs of stress and adjust the exposure time accordingly.
Comparison of tunnel cover materials
| Material | Heat Retention | Ventilation | Primary Use |
|---|---|---|---|
| Clear Polythene | High | Low | Pre-warming soil, early germination |
| Horticultural Fleece | Moderate | High | Frost protection, pest exclusion |
| Insect Mesh | Low | Very High | Pest control, wind protection |
| Black Polythene | Moderate | Low | Specific blanching or bare-soil covering |
Useful products for this job
The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.
- Horticultural fleece: Used as a breathable cover for tunnel cloches to provide frost protection and pest exclusion. Check the weight (g/sq m); 17g is lightweight for early crops, while 35g provides more protection for tender plants. Search Amazon for Horticultural fleece.
- Clear polythene sheeting: The primary material for trapping heat to pre-warm soil in early spring. Ensure the material is UV-stabilised for garden use to prevent rapid degradation in sunlight. Search Amazon for Clear polythene sheeting.
- Drip irrigation kit: Provides a way to water plants inside cloche tunnels without having to lift the covers. Ensure the tubing is flexible enough to be laid along the length of the tunnel bed. Search Amazon for Drip irrigation kit.
Related garden guides
- How to store crop covers so they last longer
- Growing salads in a greenhouse through the cooler months
- More greenhouse & growing guides
Sources and further guidance
- Cloches: How to Use Them | RHS Advice
- Fleece and crop covers | RHS Advice
- Warming Soil for Planting | RHS Advice
Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.