A garden cloche is a protective covering placed over plants, essentially acting as a miniature, portable greenhouse. The word “cloche” is French for “bell,” referencing the traditional bell-shaped glass covers used by market gardeners centuries ago. This tool creates a controlled environment around a single plant or a small row of plants. By protecting vulnerable seedlings and crops from the elements, the cloche helps gardeners start early and extend the growing season.
Defining the Modern Cloche and Its Purpose
The function of a cloche is to create a localized microclimate that is more favorable than the surrounding external conditions. This effect is achieved through trapping solar radiation, similar to a full-sized greenhouse. Transparent materials allow sunlight to pass through and warm the soil and the air inside. This trapped heat, known as the greenhouse effect, retains warmth and insulates the plant from sudden drops in temperature, especially overnight.
The retained warmth prevents damage from light frost and encourages earlier seed germination by pre-warming the soil. Cloches also reduce transplant shock. Furthermore, the physical barrier shields young plants from harsh winds, heavy rain, and common garden pests, preventing animals and insects from accessing the vulnerable foliage.
Common Designs and Materials
The traditional design remains the glass bell cloche, which is heavy, durable, and provides excellent heat retention due to the properties of glass. These individual, bell-shaped covers are often used for single, high-value plants or for decorative purposes. Since glass is fragile and expensive, modern alternatives have become common.
Modern cloches often utilize rigid or flexible plastic, offering a lightweight, shatterproof, and affordable solution. Rigid plastic cloches, often made from polycarbonate, may resemble small domes or miniature cold frames. For covering long rows, the tunnel cloche is popular, consisting of plastic film or horticultural fleece stretched over hoops. Flexible plastic must be securely anchored to the ground to prevent wind displacement.
Operational Use and Seasonal Management
Successful cloche use requires proper timing and careful management of the internal environment. Cloches should be placed over the planting area one to two weeks before sowing or transplanting. This pre-warming step creates an optimal temperature for root development and early growth. Cloches are most effective in the spring to start the season early and in the fall to extend the harvest.
The most crucial management task is ventilation, as the insulating effect can quickly become detrimental on sunny days. Temperatures inside a closed cloche can rise rapidly, potentially scorching plants through heat stress. To prevent this, the cloche must be opened or lifted daily to allow air circulation, releasing excess heat and preventing damaging humidity buildup.
Gardeners typically open the cloche during the warmest part of the day and close it in the late afternoon to trap residual heat for the night. Once the threat of frost passes, plants must be hardened off before the cloche is removed completely. Hardening off involves gradually increasing the time the plant is exposed to the outside air over several days, preparing it for the unprotected garden environment.