A cloche (pronounced klōsh) is a small, portable protective covering designed to shield plants from adverse weather and environmental conditions. The term originates from the French word for “bell,” referencing the shape of the earliest versions of this gardening tool. Its purpose is to create a localized, moderated environment, functioning much like a miniature greenhouse within the garden setting. This structure helps gardeners gain control over the immediate growing conditions for individual plants or small rows of crops.
Defining the Garden Cloche
The garden cloche operates by creating a microclimate around the plant, which is the core mechanism behind its utility. This effect is achieved by trapping solar radiation that passes through the transparent or translucent material, warming the air and soil beneath the cover. The structure also helps to minimize the loss of this accumulated heat and moisture to the cooler ambient environment, especially during nighttime hours.
The concept dates back to 17th-century France, where market gardeners, known as maraîchers, used hand-blown glass bell jars extensively in their intensive vegetable farms. These original glass cloches became a recognized feature of the French kitchen garden (potager), establishing the principle of using a portable barrier to buffer plants from temperature extremes and wind desiccation.
Common Materials and Forms
Modern cloches come in diverse materials and configurations, catering to different gardening needs and scales.
- Glass cloches are traditional and prized for superior insulation and heat retention due to their weight and density. However, glass is fragile, heavy, and typically more expensive than contemporary options.
- Rigid plastic or polycarbonate cloches are a popular alternative, offering excellent light transmission while being lightweight and durable. These often feature built-in vents and are easier to handle and store than their glass counterparts.
- Tunnel or row cloches cover longer areas using flexible hoops, often made of wire or PVC, covered with clear plastic sheeting.
- Fabric or fleece covers are highly breathable, reducing the risk of overheating and fungal issues. They provide light frost protection by preventing heat from radiating away from the plant surface.
- Mesh or netting cloches primarily serve as a physical barrier against pests while allowing full air and water circulation.
Key Functional Applications
One primary application of the cloche is to extend the growing season. By placing a cloche over a planting bed, gardeners can pre-warm the soil weeks before safe outdoor planting dates, encouraging earlier seed germination and allowing for earlier transplanting. This focused warmth helps heat-loving crops thrive in cooler spring conditions.
Cloches provide frost and cold protection by insulating plants from unexpected drops in temperature, especially during the vulnerable periods of early spring and late autumn. The trapped heat and material barrier can provide several degrees of temperature moderation, safeguarding tender plant tissue from freezing damage. This protection is especially useful overnight.
The physical nature of the cloche also makes it an effective pest and disease exclusion tool. It acts as a shield against common garden threats like birds, rabbits, and various chewing insects that target young seedlings. Furthermore, by keeping rain off the foliage, cloches can mitigate the spread of certain moisture-dependent fungal diseases.
Cloches also play a role in the hardening off process, which is the gradual acclimatization of tender plants grown indoors to outdoor conditions. By placing the plants under a cloche for increasing periods, gardeners can slowly introduce them to outdoor temperature fluctuations, wind stress, and direct sun exposure before permanent planting. This controlled transition minimizes transplant shock.
Proper Deployment and Management
Successful cloche use depends heavily on active management, particularly concerning temperature regulation.
Ventilation
Ventilation is necessary to prevent the temperature inside a rigid cloche from soaring on a sunny day, which can scorch plant tissues in a matter of hours. When ambient temperatures rise above 50°F (10°C), cloches should be propped open, lifted, or have their vents fully exposed to allow excess heat and humidity to escape.
Moisture Management
Managing moisture levels is important, as the cloche prevents natural rainfall from reaching the soil. Plants under rigid covers require careful monitoring and watering at the base to ensure adequate hydration. However, the cover also reduces water loss through evaporation, meaning the frequency of watering is typically less than for uncovered plants.
Timing of Removal
The timing of removal is crucial for long-term plant health, as leaving a cloche in place too long can weaken the plant. Cloches should be permanently removed when the threat of frost has reliably passed and nighttime temperatures have stabilized above the minimum threshold for the specific crop.
Anchoring
Anchoring is required to prevent wind from displacing lightweight or tunnel forms, which could damage the plants or the cloche itself. This can be accomplished by banking soil around the base, using heavy stones, or securing the cover to the ground with stakes or specialized clips.