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Tomatoes 2008
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To get the most out of a garden, you can extend the growing season by sheltering plants from cold weather in early spring and during fall. Very ambitious gardeners harvest greens and other cool-weather crops all winter by providing the right conditions. There are many ways to lengthen the growing season; your choice depends on the amount of time and money you want to invest. Coldframes and Hot Beds Coldframes, sun boxes and hot beds are relatively inexpensive, simple structures that provide a favorable environment for growing cool-weather crops in early spring, fall and even into winter months (Figure 6.10). Some are elaborate and require a large investment, but may be the best option for those who are serious about having fresh vegetables during winter. Coldframes and sun boxes have no outside energy requirements, relying on the sun for their source of heat. Hot beds are heated by soil heating cables, steam-carrying pipes or fresh, straw-filled manure buried beneath the rooting zones of plants. Heat is collected by these frames when sunlight penetrates the sash made of clear plastic, glass or fiberglass. To ensure good drainage and maximum solar absorption, the ideal location for a coldframe is a southern or southeastern exposure with a slight slope. A sheltered spot with a wall or hedge to the north will provide protection against winter winds. Sinking the frame slightly into the ground also provides protection by using the earth for insulation. A walkway in front of the frame, adequate space behind the frame to remove the sash and weights to raise and lower the glass sashes make using a frame easier. Some coldframes are lightweight enough to move between sections of the garden. Another possibility is the Dutch light, which is a large, portable, greenhouse-like structure that can be moved from place to place. Passive solar energy storage is utilized in coldframe design. For example, barrels painted black and filled with water absorb heat during the day and release it at night. The solar pod provides this type of heat storage. Other coldframe designs are very well-insulated and have a high back and a steep glass slope. Some have movable insulation that is folded up during the day and folded down at night or during extremely cold weather to protect growing plants. A coldframe is also useful in early spring to harden-off seedlings which were started indoors or in a greenhouse. This hardening-off period is important as seedlings can suffer serious setbacks if they are moved from the warmth and protection of the house directly to the garden. The coldframe provides a transition period for gradual adjustment to outdoor weather. It is also possible to start cool-weather crops in a coldframe, either transplanting them to the garden or letting them grow to maturity in the frame. Spring and summer coldframe uses center around plant propagation. Young seedlings of hardy and half-hardy annuals can be started in a frame many weeks before they can be started in the garden. A portion of the soil can be replaced with sand, peat moss or some other suitable medium to root cuttings or to start sweet potato slips. Fall is a good time to sow some cool-weather crops in frames. With adequate moisture and fertilization, most cool-season crops will continue to grow through early winter in the coldframe’s protected environment. Depending on the harshness of winter and whether additional heating is used, your frame may continue to provide fresh greens, herbs and root crops throughout cold winter months. Growing frames can be built with a variety of materials, but wood and cinder blocks are the most common. Wooden frames are not difficult to build. Use decay-resistant wood, such as high quality cypress, or choose pressure-treated wood. Kits are commercially available and can be easily assembled; some kits even contain automatic ventilation equipment. There is no standard size for a coldframe. Frame dimensions depend on the amount of available space, desired crops, the size of the window sash and the permanency of the structure. Do not make the structure too wide for weeding and harvesting; 4 to 5 feet is about the maximum width to comfortably reach across. The frame sash should be sloped southward for maximum sunlight exposure and absorption. Insulation may be necessary if a sudden cold snap is expected. A simple method is to throw burlap sacks filled with leaves over the frame sash at night to protect plants from freezing. Another method is to stack bales of straw or hay against the frame. Ventilation is most critical from late fall through early spring on clear, sunny days when temperatures rise above 45°F. The sash should be partially raised to prevent the buildup of extreme temperatures inside the frame. Lower or replace the sash early enough to conserve some heat for evening. In summer, extreme heat and intensive sunlight can damage plants. This may be avoided by shading with lath sashes or old bamboo window blinds. To help reduce disease problems, water plants early in the day so that they will be dry before dark. It is possible to convert a coldframe to a hot bed. For a manure-heated bed, remove 2 feet of soil (for better drainage, remove more soil and add a layer of gravel). Add an 18-inch layer of straw-filled horse manure and then cover with 6 inches of good soil. For an electric-heated bed, remove 8 or 9 inches of soil. Place thermostatically-controlled electric cable in 6- to 8-inch loops on the soil, evenly spacing the cable but not allowing it to cross itself. Cover the cable with 2 inches of sand or soil, and then place hardware cloth on top to protect the cable. Finally, cover this with 4 to 6 inches of good soil. Cloches and Row Covers The cloche (pronounced klosh) was originally a bell-shaped glass jar set over delicate plants to protect them. However, many types of portable structures which shelter plants from drying winds and cold air are now defined as cloches. Cloches provide a greenhouse-like atmosphere for seeds and small plants in order to get an early start on the season or to extend the fall garden as long as possible. They are either placed over individual plants or can be tunnel-shaped to cover whole rows (Figure 6.13). Cloches trap solar radiation and moisture evaporating from the soil and plants. Simple forms are a hotkap or plastic jugs cut in two pieces. More elaborate cloches include fiberglass tunnels, special plastic cloches or row covers with slits in them to provide aeration, as well as panes of glass connected by specially designed hinges to form a tent. There are a variety of forms on the market now, some more effective than others, and some can be easily constructed from household materials. Cloches are generally lightweight, portable and reusable. It is preferable to have a design that can be completely closed at night to prevent frost damage and opened or removed during the day for air circulation. Cloches should either be anchored down or be heavy enough not to blow away. Greenhouses There is an abundant selection of greenhouses on the market, and building plans for even more types are available. If you intend to purchase or build a greenhouse, thoroughly investigate all the available options, preferably visiting as many home greenhouses in operation as possible. List your needs and wants ahead of time and determine what uses you have in mind for your greenhouse. Compare the various alternatives on that basis. Many companies will send free specifications and descriptions of the greenhouses they offer; look in gardening magazines for advertisements. The conservation-minded person may find an attached solar greenhouse desirable even though the initial cost is generally higher than that of a simple, freestanding, uninsulated greenhouse. For maximum effectiveness and lower heating costs, the north and side walls can be insulated, leaving liberal glass area for winter sunlight absorption on the southern side. Adding some type of solar radiation storage also increases the energy potential of solar greenhouses. When attached to a house, these greenhouses can provide supplemental household heat, but there is a trade-off between heating the home and growing plants in the greenhouse (especially heat-loving plants). Some researchers have concluded that a good compromise is to grow cool-weather crops during the winter in an attached solar greenhouse instead of crops that have high heat requirements, such as winter tomatoes. Shading It is not always easy to start seeds or young plants for fall crops in the hot, dry conditions of July and August in New Mexico. One simple way to provide shade in an otherwise exposed area is to build a portable shade frame for placing over rows after seeds are sown or transplants are set out. This can be the same type of frame used to start early seeds but with lath strips or an old bamboo shade instead of plastic.
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