Cold frames are one of the oldest forms of greenhouses. A cold frame is essentially a glass box with aluminum framing and a lid. Its main function is to extend the growing season into early spring and late fall. A cold frame is placed directly above a section of soil where plants will be grown. During the night and cold days, the lid is kept closed to retain heat, providing plants with necessary warmth. Then, when the days are warm, the lid is opened for fresh air and lower temperatures.
In early spring, seedlings can be transplanted into a cold frame and gain an early start on the season. By raising seedlings directly in the cold frame, there is no adjustment to the outside. The cold frame is an excellent choice for cold weather plants like lettuce, spinach, and radishes in early spring. Plants can also be nurtured in a cold frame while they remain in a container (for a hardening-off period), with the intention of transplantation into an outdoor garden.
Flowers are often located in a cold frame during summer months with the lid open. Heat loving vegetables, like peppers and tomatoes, can also be raised in the cold frame over summer. In late summer, cool weather crops are again planted in the cold frame to extend the growing season. Peas, broccoli, and lettuce are common choices. Most gardeners enjoy forcing bulbs, and this can be done in the cold frame. Traditional flower pots can be planted with the bulbs and allowed to overwinter inside the cold frame. When the first leaves emerge, the containers are removed from the cold frame and brought into the house. Another option is to plant the bulbs directly into the cold frame and wait for spring blooms, ahead of when nature grows.
Cold frames are historically constructed out of wood, which is subject to rotting after a few years and will require frequent maintenance. Solar Innovations®’s cold frames are constructed out of aluminum, which will not rot, warp, or rust. Each unit is custom designed to your exact specifications; customers may choose their dimensions and include as many bays as needed. Cold frames are available in all of Solar Innovations®’s standard colors.
Lids are held by one of two ways, both of which are weather resistant. One option is to use a manual operation hinge. The lid lifts to different degrees of openness, allowing various amounts of air into the cold frame. The second option is an automated operation, which opens and closes depending on the temperature. Insulated, clear tempered glazing is generally used in cold frames. This choice of glazing ensures plenty of sunlight will penetrate the frame and the tempered glass provides impact resistance. By using insulated glass, the cold frame has greater insulation than a single monolithic sheet of glass. The sides of the cold frame can consist of solid glass or aluminum panels.