Using cold frames is a great way to extend the growing season. These sturdy structures are highly effective in protecting plants and seedlings from cold weather. They comprise a variety of models, including some that are sold in pre-packaged kits. For those who want to keep costs to a minimum, building a makeshift cold frame (right) from a few basic materials provides a quick and easy alternative to a store-bought model.

Space and budget are the two major considerations in choosing the right cold frame; most models feature a slanted design that allows rain and snow to slide off.

Pre-packaged cold frames are generally made of hard, durable polycarbonate plastic and are able to effectively resist hail and other adverse weather conditions.

Kits with built-in frames generally feature a simple design that requires only a hammer for complete assembly.

To ensure that a cold frame is able to absorb a sufficient amount of heat during the day, place the structure along a home's southern or western exposure.

During the hours when the frame is absorbing heat, prop the door open with a wooden dowel to provide ventilation and encourage air circulation (see right). In the evening, close the lid to protect the plants from cold temperatures.

Cold frames are great for over-wintering plants as well as starting seeds. (Note: When starting seeds in a cold frame, it may necessary to provide "bottom heat" (from a source like a heat mat) to get seeds started.)

Cold-tolerant varieties that make good choices for cold frames include pansies, violas and most vegetables.