A cloche is a small, portable plant covering designed to be easily moved around the garden. A cloche traps the sun's warmth raising the temperature of both the air and soil inside.
A cloche can cover a single plant or a small group of plants. You can use a cloche to protect a plant from an overnight frost or chilling winds. Cloches are commonly made of plastic or glass. A gallon milk jug with its bottom cut out can be used as a cloche.
Cloches are not a long-term solution to protecting plants. Because they are small they do not retain enough solar heat to sustain plants when temperatures fall below 40°F for more than a day. Conversely, because a cloche is small and has no venting other than lifting it away from the plant, the temperature inside a cloche can quickly overheat (the smaller the cloche the quicker it will overheat).
In late spring and early fall when the weather and temperatures are unsettled, the daily and nightly use of cloches may keep plants protected enough to add 2 to 4 weeks to your garden's growing season.