Cold frames, hotbeds make it possible to plant the vegetable garden, blooms early

It’s the end of winter and that’s the time of year when gardeners want to start planting something.


Although vegetable and flower seeds can be sown indoors, this process requires a good amount of space, additional lighting and constant soil moisture management, which can be difficult to control. It can also be messy, as I discovered last year when I spilled potting soil on the basement carpet!

For gardeners looking to take a spring leap, a simple cold frame or warm bed structure allows for late winter seeding of cool season crops and earlier outdoor planting of warm season crops in late winter. spring. These small structures can also be used later in the spring to harden off or acclimate warm season seedlings grown indoors or in a greenhouse to outdoor conditions.

Cold frames and greenhouses require ventilation during the hot days of early summer.

Cold frame: think of it as a mini greenhouse

A cold frame is a simple, low-tech, box-like structure with a glass or plastic cover and is designed to capture passive energy from the sun, providing a favorable environment for the growth of cool-season crops at the late winter and early spring. These small structures collect heat as the sun’s rays shine through the glass or plastic covering, providing warmth inside the cold frame similar to the heat generated inside a greenhouse. Cold frames can be placed directly on the ground or on raised beds. For additional insulation, cold frames can be installed several inches below ground level or surrounded on all sides by straw bales.

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Cold frames and cold frame kits can be purchased online or at major garden centers, but gardeners who are comfortable with tools can easily construct a cold frame with wood and glass or polycarbonate plastic. . Old windows salvaged from home window replacement projects make great covers for cold frames and fireplaces.

Fireplaces: Cold frames with underfloor heating

Hearths are the same structures as cold frames, but include additional heating provided by floor heating cables or electric tapes placed under the floor in the structure. As an alternative to using electricity to provide supplemental heat, manure made from straw can be placed under the ground in a warm bed, and as the manure decomposes, heat is produced, increasing the temperature of the ground and the air in the structure.

mike hogan

To build a manure-based fire pit, remove about 10 inches of soil from under the structure, add a small amount of gravel for drainage, add 18 inches of straw-based horse manure, and cover with about 6 inches of soil.

Start cool season crops first

In central Ohio, cold frames and hotbeds typically allow gardeners to plant cool-season crops three to four weeks earlier than seeds planted in unprotected soil. Depending on the weather, this means that these crops can be planted as early as late February and early March in cold frames and hotbeds.

The most cold-tolerant cool-season vegetables that can be planted the earliest in cold frames and hearths include kale, Swiss chard, spinach, mesclun, green onions and even peas. Lettuce, cabbage, greens, cabbage, radishes and perhaps beets, carrots and broccoli should be planted two weeks later. When selecting vegetable varieties to start in a cold frame or hearth, be sure to select the most cold hardy varieties available.

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Warm season crops such as peppers, tomatoes, squash, eggplant, melons, cucumbers and beans should not be planted in cold frames or hotbeds until early or mid-April. It is extremely difficult to grow cold season and warm season vegetables simultaneously in the same cold frame or warm bed due to the different temperature requirements.

Starting Flowers in Cold Frames

It is also possible to start cold-tolerant herbaceous annuals and perennials in late winter in a cold frame or hotbed. Annual flowers that tend to do best in a cold setting or fire include snapdragon, calendula, ageratum, celosia, cosmos, sunflower, cornflower, alyssum, and marigold. Herbaceous perennials that can be started in a cold frame or hotbed include aster, astilbe, blazing star, coreopsis, penstemon, phlox, yarrow, carnation, coneflower, salvia , coralbells and hollyhock.

Cold frames and fire pits rely on passive solar energy to provide heat inside the structure.

Management of cold frames and hotbeds

Ventilation will be needed in cold settings and fireplaces in early spring or anytime when daily outdoor temperatures reach 45 degrees Fahrenheit. Opening the top of these structures will prevent the buildup of extremely hot temperatures, which can result in weak, spindly plants.

Although the soil inside a cold frame or fire pit rarely requires supplemental watering during periods of cold temperatures, the warmer temperature periods typically experienced in early spring can dry out the soil, requiring irrigation. additional.

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So if you’re looking forward to jumping into spring planting, head to your garage or workshop and build a cold frame or fire pit so you can start planting cool-season crops within the next few weeks.

Luz W. German