One year, days after I had set out the plants I'd tenderly started from seed, killing frost was in the forecast. At dusk, I rushed to the garden with my collection of glass jars and placed one over each cherished seedling. As the weather warmed during the day, I had to uncover the plants so that they wouldn't be steamed to death and then cover them again before sunset.
It was my version of "cloche gardening." French market gardeners in the 19th century used to place large bell-shaped jars over plants in spring and fall to act as miniature greenhouses. Cloche is the French word for "bell," and by extension the bell jar ... and eventually, the hat that resembled both.
There must be an easier way to save tender plants from late frost!
A fellow master gardener saves translucent plastic gallon jugs. She cuts off the bottom, tosses out the caps and places one over each transplant. Because she can water through the vent, she leaves the jugs in place until the plant foliage fills the jugs. Needless to say, I started a jug collection as soon as she shared this technique.
For row crops, covers can be constructed either by bending and securing fiberglass panels over each row or by building a wooden or wire frame covered in clear plastic. On hot days, the plastic must be folded back. The idea is to bring the greenhouse to the garden.
Floating fabric row covers are easier to use because they do not require a supporting framework and do not need to be adjusted on sunny days. Lighter-weight fabric (0.5oz/sq. yd.) is intended to protect crops from insects, so be sure to buy a heavier weight fabric to protect from frost. Anchor the row covers well so the wind can't blow them away.
Cold frames are another way to get an early start. The structure should face south or southeast so that the sun warms the glass lid. One gardening friend uses bales of straw for walls. This would work well on a slope where the wall won't shade the plants. The back wall should be taller than the front one. On warm days, the glass ceiling needs to be propped open.
The cold frame can be used in spring as either a place to start an early garden or to harden off transplants. "Hardening off" refers to the process of acclimatizing seedlings started indoors before planting them in the garden.
When would the gardener use a glass bell cloche?
Ornamental as it may be, it is most practical today as a garden accent.
Master gardener Ann Bartlett never lets lack of familiarity with a plant stop her from trying it in the ornamental beds around her home.
(Photo from the catalog ukgardensupplies.co.uk)