Dawn McKeown, age 12, of New Bedford, Mass., for her question:

WHAT IS A COLD FRAME?

A cold frame is a covered box built on the ground to protect growing plants. It has no bottom and may vary from six inches to two feet or more in height, depending on the kind of plant it contains. The top of a cold frame is made higher in the back to receive sunlight.

Different cold frame covers are used for different purposes. Glass or transparent plastic covers prolong the growing season by trapping heat and protecting plants frog wind and cold weather.

Cold frames may also be used to start plants early in the season.

For plants that need shade, frames may be covered with spaced slats, burlap or other material that reduces the amount of light entering the box. To protect plants during the winter, cold frames are covered with boards or straw mats.