1. Sunlight. Tomatoes require a minimum of 8 hours of continuous sunlight each day.

2. Temperature. Tomatoes need 3 to 4 months of warm, clear, fairly dry weather to produce best. Tomatoes need consistent night temperatures between 55°F and 75°F to set fruit. (A few varieties will set fruit at lower or higher temperatures.) Fruit will not color properly when night temperatures stay above 85°F, and plants will quit growing when temperatures go above 95°F.

3. Continuous and even watering. Keep the soil evenly moist--not too wet and not too dry. Too much water will drown the plant; too little water will stop fruit production. Test soil moisture by sticking your finger into the soil--if it comes out dry, it's time to water; if it comes out wet, hold off. During periods of drought deep water tomatoes once a week. A constant, even supply of water can prevent blossom end rot, but too much water will cause it.

Continue reading Tomato Success at the next page:

4. Continuous feeding. Prepare the tomato-growing bed with well-rotted garden compost and a trowelful of aged manure added to the soil where each plant will grow. Add a trowelful of bone meal into the bottom of each hole--the extra phosphorus will speed ripening. Too much nitrogen will give you abundant foliage but delay ripening. Add nitrogen when the top leaves turn yellow and the stem become deep purple.

5. Loose, well-drained soil. But almost any garden soil will grow tomatoes. Sandy loam is best for early tomatoes. Heavy clay loam is ideal for late tomatoes. Amend the soil with aged compost before planting. Tomatoes prefer a soil with a pH between 6.0 and 7.0, just below neutral in acidity.

6. Protect leaves and roots. Protect the tomato plant from extremes of temperature--cold and hot, strong winds, weeds, pests and diseases. Set 8 to 10 week old tomato seedlings in the garden two weeks after the last frost in spring. If transplanted sooner, tomatoes must be protected from cold temperatures with hot caps or plastic tunnels. Place tomatoes in the garden where they will be protected from drying winds. Protect plants from cutworms with a paper collar set in the soil at transplanting. Examine plants often to be rid of tomato hornworms and other pest early. Avoid fungal and bacterial diseases by watering at the base of plants and rotating tomatoes to new beds each year. Where summer temperatures exceed 95°F, shade cloth protection will protect leaves and fruit.

Related Tomato Growing Articles:

How to Choose a Tomato for Your Garden

How To Grow Tomatoes

Tomato Types

Crack-Resistant Tomato Varieties

And more at the Tomato Growing Archives

The Kitchen Garden Almanac for March: Cool and Cold Regions

The Kitchen Garden Almanac for March: Warm Regions

If you are looking for a vegetable garden calendar of tasks and planting suggestions for the year, here it is:

Vegetable Garden Calendar

And if you are struggling with very cold weather, do not forget the cold frame to get the spring garden started:

Cold Frame Calendar

As well, now is the time to visit the Seed Starting Category for articles on getting your crops growing.

Heavyweight rows covers and garden blankets or quilts are used to protect plants from cold temperatures, chilling winds, and frosts--most often in late autumn, winter, and early spring. Lightweight floating rows covers are used to shield plants from insects and diseases in spring and summer. Shade cloth is used to shade soil and plants in hot summer weather.

Row covers and floating row covers are commonly made form spun bonded polyester or polypropylene fabric--often called horticultural cloth. Heavyweight covers are used to extend the growing season by keeping plants up to 10°F warmer during the day and 2° to 3°F warmer at night. Lightweight covers are used to exclude insects but are thin enough to allow light, water, and air to reach plants.

Row covers can be draped over hoops or frames set above rows of plants (to form protective tunnels) or they can be laid loosely or floated over plants. Medium to heavy weight row covers weighing from 1¼ to 2 ounces per square yard should be partially lifted on hot days and removed as the season advances to prevent plants from overheating.

Horticultural cloth for covering plants is commonly sold in squares or rolls and is easily cut to size to cover one plant or an entire row. Covers can be held in place by garden staples, soil, boards, or bricks. A floating row cover set in place when seeds are sown or seedlings set out should have enough material for 4 to 6 weeks of plant growth, allowing the cover to float up with plant growth.

Row covers used to protect plants from frost or freezing weather should be lifted up or supported by a frame so that the fabric does not touch plant leaves. Fabric touching plants can wick killing cold temperatures to plant tissue.

Row covers can extend the growing season in cold-winter regions by 3 to 4 weeks in both spring and fall giving seeds and seedlings a faster start and protecting maturing crops until harvest. In warm-winter regions, row covers can protect plants all through the winter and greatly prolong the growing season and harvest.

Use row covers to:

• Warm and speed the growth of seeds and seedlings in spring and protect crops from late frosts.

• Slow the evaporation of soil moisture.

• Protect plants from wind, heavy rain, and hail.

• Keep pests off plants (and stop the spread of disease by insects); be careful not to trap pests under row covers. (Covers will not protect plants from insects that emerge from the soil such as flea beetles, root maggots, tomato hornworms, Japanese beetles, and Colorado potato beetles.)

• Protect late summer crops from fall frost and extend the harvest.

• Protect crops from hot temperatures and burning sun rays.

Row covering weights: Row covers are measured or graded by the weight in ounces per square yard of fabric. Heavyweight covers weigh 2 ounces per square yard; medium weight covers weigh 1¼ ounce per square yard; lightweight covers weight a half ounce per square yard.

• Heavyweight row covers. Heavyweight covers (2 ounces per square yard), also called garden blankets or quilts, are commonly made of thick, close knit polypropylene fibers. These covers are best supported above plants by plastic or fiberglass hoops or wooden frames.

Heavyweight covers can protect plants to 24°F and are commonly used in late winter or early spring to protect plants from frost or short freezes allowing the growing season to begin as much as 3 to 4 weeks earlier than average.

In cold-winter regions, heavyweight covers also can be used in late autumn and early winter to keep freezing weather from harming crops until harvest and delay soil freezing (protecting root crops). In mild-winter region, heavyweight covers can used to protect root and leaf crops for harvest all winter or wintering over crops for early spring harvest.

Heavyweight row covers block from 40 to 50 percent of sunlight and are best not used once temperatures have settled above freezing and plants begin active growth. The temperature under a heavyweight cover in warm weather can rise to as much as 20 degrees warmer than the outside temperature

• Medium-weight row covers. Medium-weight or all-purpose row covers (1¼ ounces per square yard) are commonly made from spun-bonded polyester or polypropylene knitted fabric and are placed on supports over young crops or floated over the tops of stronger, mature plants.

Medium-weight row covers protect plants from frost damage down to 28°F (2 to 6 degrees of protection). These covers will protect plants from strong winds, heavy rain, and even hail but allow light, air, and water to reach plants.

Medium-weight row covers allow from 70 to 85 percent of sunlight to reach plants and can be used for light shading in summer. Medium-weight covers also can be used to exclude insects and other pests early in the growing season.

• Light-weight row covers. Light-weight or summer-weight row covers (one-half ounce per square yard) are used to protect plants from insects, birds, and insect-borne diseases. Light-weight row covers transmit up to 95 percent of sunlight to plants. These covers are not used for frost protection, will not overheat plants in hot weather, and readily allow rain and irrigation to reach plants.

• Shade cloth. Akin to row covers is shade cloth. Shade cloth is a knitted fabric often made from polyethylene or polypropylene. Shade cloth is commonly attached to a frame and set above heat sensitive crops in summer. It can extend the growing season of crops such as lettuce and spinach which bolt or flower and go to seed if allowed to sit in the hot sun.

Shade cloth is available in a range of densities to provide 30, 40, 50, 60, 70, 80, or 90 percent shade. A density of 60 percent or less can be used for heat sensitive crops such as salad greens.

Shade cloth should sit at least 24 inches off the ground to minimize the buildup of heat and allow for the circulation of air. Support shade cloth with wire or plastic hoops or on wooden stakes or frames set up over crops.

Seasonal use of garden fabric and row covers:

• Spring. Prepare the soil and sow seed or set out transplants. Place or float garden fabric on the ground directly over sown seeds or seedlings or drape the fabric over hoops or a support structure. Do not stretch fabric tight over seedbeds; allow the cover to float upwards with plant growth. Fabric over hoops can be stretched tight. Anchor the edges of covers in place with garden staples or soil.

Be sure to lift or vent the fabric during the day once daytime temperatures begin to warm to greater than 70°F (remember temperatures underneath the cover can be 10°F or more warmer). Do not allow plants to overheat which will result in wilting and leaf or blossom drop.

Allow pollinating insects such as bees to reach crops that require insect assistance for pollination. (Insect-pollinated crops include beans, peas, pumpkins, squash, and strawberries.) Lift or remove fabric covers during the day when plants begin to flower. For self-pollinating plants such as tomatoes and peppers, covers can remain in place as long as temperatures do not rise to greater than 85°F; when temperatures rise too warm tomato pollen will become sterile and peppers will not set fruit.

Horticultural cloth will block insects from reaching plants (including aphids, potato beetles, Japanese beetles, grasshoppers, leaf miners, cabbage worms, root maggots, and some vine borers) as long as the edges of the cloth are secured. (But garden fabric will not exclude insects that emerge from the soil from insect eggs in the soil before the soil was covered.)

• Summer. Use lightweight garden fabric or shade cloth to protect plants from hot temperatures and intense summer sunlight. Garden fabric and shade cloth will keep soil and plants temperatures cooler. Horticultural cloth will slow soil moisture evaporation.

Choose shade cloth according to the intensity of the sun in your region. Shade cloth is available in weaves that will provide 30, 40, 50, 60, 70, 80, or 90 percent shade. A weave density of 60 percent or less can be used for heat sensitive crops such as salad greens.

Set shade cloth at least 24 inches off the ground to minimize the buildup of heat and allow for the circulation of air. Support shade cloth with wire or plastic hoops or on wooden stakes or frames set up over crops.

• Fall. Use medium-weight garden fabric in autumn to protect cold-sensitive crops such as tomatoes and peppers from early frosts or chilling winds. Row covers put in place in the fall slow the dissipation of soil heat built up over the summer and reserve daytime solar heat into cooling autumn nights. As daytime autumn temperatures continue to drop, medium-weight fabric can be replaced with heavyweight fabric; these fabrics should be supported by hoops or structures.

Row covers used in autumn can extend the harvest of warm-weather crops by two to three weeks in almost all regions, longer in mild-winter regions. Row covers can extend the growing season for fall cool-weather crops by a month or more.

• Winter. Medium- and heavyweight row covers in mild-winter regions can be used to extend the growing through the winter. Leaf and root cool-weather crops can be protected by row covers for harvest or storage through the winter. In cold-winter regions replace row covers with plastic in winter to create a coldframe or cold-weather plastic tunnel.

Common commercial brands of horticultural cloth: Horticultural cloth for row covers is sometimes sold under brand names including Remay, Agribon, Harvest Guard, Typar, and Agryl.

Related Articles:

Plastic Tunnels for Growing Vegetables

Cold Frame: Extend Your Vegetable Garden Season

Making a Cold Frame

Cloche to Protect Plants

Cold Frame Calendar

A cloche can cover a single plant or a small group of plants. You can use a cloche to protect a plant from an overnight frost or chilling winds. Cloches are commonly made of plastic or glass. A gallon milk jug with its bottom cut out can be used as a cloche.

Cloches are not a long-term solution to protecting plants. Because they are small they do not retain enough solar heat to sustain plants when temperatures fall below 40°F for more than a day. Conversely, because a cloche is small and has no venting other than lifting it away from the plant, the temperature inside a cloche can quickly overheat (the smaller the cloche the quicker it will overheat).

In late spring and early fall when the weather and temperatures are unsettled, the daily and nightly use of cloches may keep plants protected enough to add 2 to 4 weeks to your garden's growing season.

There are several types of cloches:

• Glass bell jars. Old-fashioned glass cloches are heavy and breakable.

• Plastic jugs and bottles. A one gallon plastic jug or a larger water bottle with the bottom removed can be used to keep light frosts off plants and keep seedlings warm in cool spring weather. The cap can be unscrewed for ventilation when temperatures rise. In cold weather loose mulch can be heaped up around the sides for extra protection.

• Tent and barn cloches. These are small, portable A-frame or box structures made of panes of glass or sheets of rigid plastic. They are commonly held together with springs, wires, or metal clips. They can be closed off on each end and adjusted for ventilation. Tent and barn cloches are commonly about 24 inches long and 9 to 18 inches tall. Open-ended tent and barn cloches can be lined up to protect a row of plants. Hinged rigid polyethylene tent and barn cloches are easily folded and moved or stored.

• Tunnel cloches. Similar to plastic tunnels, tunnel cloches can be made of rigid arched plastic or made of plastic sheeting, the same as plastic tunnels. 

• Protective cylinders and teepees. These are made of wire mesh or fencing wrapped with polyethylene sheeting (4, 6, or 8 mil). A tomato cage wrapped in plastic sheeting can serve as a cylinder cloche. The commercially produced Wall O'Water made of hollow polyethylene tubes joined together and filled with water is a protective cylinder cloche.

(During the day, the water absorbs heat from the sun. The heat is slowly released at night. When the cylinders are gathered together they can protect plants to a temperature of 10°F.)

• Hot caps or hot kaps. These simple plant protectors can be made out of folded newspaper, wax paper, or paper bags. They are quick protection against light frosts but will not hold up against rain or irrigation.

Using a cloche. Set a cloche over any plant that may suffer as a result of cold temperatures or chilling winds. Ideally, a cloche should be set in place early enough in the day that it will capture the warming rays of the sun heating the air and soil inside. The slight rise in temperature is usually enough to protect plant tissue from a light freeze (a freeze of just a few hours).

If you intend to leave a cloche in place for longer than a day and temperatures are expected to warm significantly during the day, be sure to allow the cloche to vent. A milk jug cloche with its cap removed is an example of a vented cloche.

Related Articles:

Plastic Tunnels for Growing Vegetables

Making A Cold Frame

Cold Frame: Extend Your Garden Season

Cold Frame Calendar

A plastic tunnel works much like a cold frame. The temperature inside a clear or opaque plastic tunnel can be heated by the sun 5 to 10 degrees warmer or more than the outdoor temperature during the day. The residual solar heat inside a plastic tunnel can keep plants 2 to 7 degrees warmer than the outdoor temperature at night.

A plastic tunnel can be portable--as small as 3 to 6 feet long, 3 feet wide, and a couple of feet tall, just large enough to grow salad greens--or nearly permanent, 25 feet long or more and tall enough to walk in. A large walk-in plastic tunnel for growing tall crops such as tomatoes is called a hoop house.

Making a plastic tunnel. Hoops for a small plastic tunnel can be made from sturdy #8 or #9 gauge wire or 5/8-inch diameter plastic tubing. The wire or tubing is arched over the growing bed and covered with 2 to 6 mil polyethylene or copolymer sheeting to form an enclosed tunnel. (Plastic sheeting is readily available at hardware stores; 1 mil equals 1/1000 of an inch. Sheeting with an ultraviolet light inhibitor is best.) Space the hoops every 2 to 2½ feet apart and arch them across the bed, 3 to 3 ½ feet wide. To make a taller tunnel set the 5/8-inch plastic hoops into rigid 1-inch diameter PVC pipe driven into the ground.

The arched hoops can be secured to a foundation or wooden raised bed frame with brackets or thrust 6 to 12 inches or more into the ground. Hold the plastic sheeting to the arches with spring-loaded clamps similar to clothes pins. The sheeting around the bottom edges and closed ends of the tunnel can be held in place with soil, wooden planks, bricks, or stones. It is important that the sheeting not be permanently secured; plastic tunnels require venting during the day when the outside temperature rises to 60°F or greater and the inside temperature reaches 80°F or more. (Plastic tunnels require the same venting as cold frames to ensure plants do not become over heated.)

Ventilation. To allow for venting, the clamps that hold the plastic in place can be removed to pull back the plastic or the tunnel ends can be left open. Alternatively, slitted plastic sheeting can be used to cover the hoops and a second sheet of unslitted plastic can be placed on top of the first layer when the temperature falls below freezing. A double layer of plastic sheeting--like a double glass sash on a cold frame--will trap air between layers for added insulation. Double thickness plastic will add 2 to 4 degrees or more greater protection against frost to the tunnel.

Snow resistance. To make a plastic tunnel that can withstand snow, use metal or plastic tubing 1 ¼ inches in diameter or greater and sheeting that is 8-mil thick. Horizontal lengths of PVC tubing also can be added to the frame at the peak and halfway down along the sides to strengthen the frame. The horizontal pieces can be fastened with duct tape or plastic zip ties. PVC tubing is commonly sold in 10 or 20-foot lengths.

Similar to the arched plastic tunnel, rigid PVC pipe ½-inch in diameter or greater can be cut into three parts and a box-like frame can be assembled using PVC elbows. The sides of the frame can be inserted into slightly larger PVC pipes driven into the ground 12-inches or more. Like a cold frame, a flat-topped plastic tunnel should have one side taller than the other to allow for the run off of rain and to keep snow from accumulating and weighing down the top of the frame.

Site. Like a cold frame, a plastic tunnel should be placed away from prevailing winds and away from cold or damp places in the garden. Growing plants inside a plastic tunnel is not different than growing plants in a cold frame; the soil or growing medium should be kept just moist, not wet, and beds should be weeded and tended just as you would in the open garden.

Summer growing. When the weather turns warm, the plastic tunnel can be lifted off of the growing bed, disassembled, or the plastic sheeting can be removed and replaced with bird netting which creates a growing bed protected from birds, rabbits, and deer during the warm-part of the year.

Plastic tent. A simple alternative to a plastic tunnel is a plastic tent. You can make a peaked plastic tent by placing plastic sheeting over a simple wooden or metal trellis frame like the kind you would use to grow pole beans up garden twine or wires. Place the sheeting over the frame and secure the sides with soil or boards.

Cool Season Kitchen Gardening Index

Cold frames can vary in size: 3 feet wide by 6 feet long is the size of an average home garden cold frame. The back side of a frame is usually taller (often 18 to 24 inches high) than the front (commonly 8 to 12 inches high) with the clear top sloping down from back to front allowing rain to run off and sunshine to flood in. The taller the frame the taller the plants it will accommodate. A home garden cold frame need be no deeper than a person's reach (24 to 36 inches); this will allow plants to be tended without stepping into the frame.

Wooden-sided frames are can be made of long-lasting wood that has not been chemically treated: well-cured pine, cypress, redwood, or chestnut can be used. The translucent top or lid of the cold frame can be made from a standard window sash--approximately three by six feet. Several sashes can be placed in a row to make a long cold frame. Sheets of Plexiglass or other plastic sheeting also can be framed to create the cold frame lid. The lid or sash is usually hinged to the back side of the frame but an unhinged lid can simply rest on the top of the frame.

Here's how you can make a simple cold frame: Construct the frame with 2 x 8 inch or 2 x 10 inch or 2 x 12 inch boards cut to size to form the box. Cut the side boards on a diagonal so that the front (southward-facing side) of the frame is lower than the back. Five-inch nails or screws and 4-inch metal fasteners can be used to hold the sides together. Hinge the lid of the frame to the back. The top can be made from an old window sash or framed Plexiglas. Set the corners of the frame slightly below grade on bricks to prevent the frame from settling. Fill in around the frame with soil to keep the cold out. You can build a higher-sided cold frame by adding framed tiers atop a framed box or an existing raised-bed frame.

If you do not want to cut the side boards diagonally, do this: Fasten two wooden stakes to the back plank; drive the stakes into the ground to about 5 or 6 inches leaving the back plank two or three inches above the ground--the back plank should, of course, be level. The front plank is sunk two or three inches into the ground and held upright by stakes on the outside, nailed on. Remove enough soil from inside the frame to bank up the side planks about halfway, thus sloping the frame from back to front. Fill in the soil along the sides and back of the frame. Attach or set on the translucent lid or sash.

The placement of your cold frame should be where the sun will strike most directly--facing south in the Northern Hemisphere--and where it will be sheltered from the north. Set the frame on the south side of a building or fence to ward off north winds. Even a hedge or low growing shrubs to the north of the frame will protect it.

Cold frames in cold winter regions. In very cold winter regions, cold frames can be fitted with insulated sides and set atop insulated foundations to retain more heat. A wooden, cement block, or solid cement cold frame can be insulated easily with the addition of 2 or more inches of Styrofoam around the inside of the frame and with a layer of 1½ inches on the bottom under the growing bed. Insulating foam can be easily cut and glued or tacked to the inside of the frame. As well foam shutters or mats can be placed atop the frame's clear lid at night. Insulation can increase night air temperature inside the frame by 8°F or even more. A double-paned glass or plastic top or a sash fitted with an under-layer of 4 to 6 mil plastic sheeting will provide additional insulation of up to 6°F.

To further insulate a cold frame in very cold winter regions, place hay bales or bags of leaves around the outside of the frame. Tarps, woven mats, and old blankets can be used to help insulate the top; this additional protection can increase the temperature inside the frame by 6°F at night. The inside of a frame can be painted white to reflect sunlight or black to retain heat. Thermal collectors as simple as masonry blocks or jugs of water set against the north wall of a frame will retain solar heat during the day that is released back into the frame at night.

Sash

The clear or translucent top or cover of the frame may be called by different names: lid, sash, glazing, or light. The top can be made of glass or rigid fiberglass, acrylic, Plexiglass, or UV-stabilized polyethylene plastic. Home-made cold frames often use old storm windows for lights. The light is usually hinged at the back of the frame for easy raising and lowering and ventilation. But a frame top can also simply slide on and off the frame.

A top sash with a double layer of glass (or plastic) is better than a single pane or layer. The space between the double layers of glass provides a cushion of insulating air between the upper and lower glass and will eliminate the need for top mats, blankets, or other covers to keep the frame warm on very cold nights.

The top should always be free to be opened to ventilate the frame. You can ventilate the frame by simply propping a stick or block under the sash. There are ways to make opening and closing the sash even easier: an automatic solar-powered frame opener attached to a thermostat can raise the top when the inside temperature inside reaches above 70°F.

Another layer of protection inside the cold frame

When temperatures are very cold, a second layer of covering inside the cold frame can add to plant protection. Poly row covers or plant blankets inside the frame will keep the temperatures around plants a few degrees warmer than the temperature inside the frame and several degrees warmer than the outside temperature. Many cold hardy vegetables can survive temperatures down to 10°F; the objective of a second covering inside the frame is to protect plants from temperatures that low.

The objective of a double cover inside a cold frame is not to extend the growing season but to extend the harvest season or to allow plants to over-winter for renewed growth in spring. Use lightweight row covers that will allow air and light to pass through. A double cover increases humidity which also increases protection.

Place row covers over crops inside the frame just before the weather gets cold enough to freeze inside the cold frame. Be sure that the row cover fabric does not touch plant tissue in freezing weather. Row covers inside the frame can be supported by wire hoops.

Earth-sided cold frame

If constructing a cold frame from wood or cement blocks is not an option, there is an alternative. You can make a temporary cold frame from earth--essentially grading up the soil around your planting bed to protect it. One way to do this is to make a sort of cold frame mold into which you can pack soil to form your earthen frame sides. Use scrap wood to make a box mold with flared sides. Place the mold along the edges of the bed where you intend to sow seeds and hill up the earth into the mold and pack it firmly with your feet or a tamper. You can then place your sash or plastic lid atop the "frame." When the weather warms and the plants are established you can use a hoe or spade to remove the earthen walls.

Related Articles:

Cold frames can be made of heavy lumber, cinder blocks, concrete, or clear plastic. The transparent top or cover is tilted toward the south or southeast to catch the sun. The back side of the cold frame is commonly six inches or more higher than the front to give a slope to the top cover (or sash) so that rain will run off and the sun's rays will strike the inside of the frame more nearly at right angles.

Cold frames can vary in size: 6 feet long by 3 feet wide is the size of an average home garden cold frame. A small cold frame is commonly no wider than a person's reach so that plants can be tended to without stepping into the frame. A typical cold frame is usually made eighteen to twenty four inches high or deep at the back sloping to twelve to eighteen deep at the front. The deeper the frame the taller the plants it will accommodate.

For most home vegetable gardeners, nearly all the plants in the vegetable garden can be started successfully in a cold frame or hotbed (a hotbed is a heated cold frame--sometimes heated by electricity or solar power or by--in decades and centuries past--decomposing steer or horse manure placed below the inside planting bed).

A cold frame can be a permanent or portable structure. The sides of a homemade cold frame can be made out of wood planks, cinder block, or brick. A temporary home-made cold frame can use bales of hay or straw for the sides. Some store-bought portable cold frames have aluminum frames and clear plastic or Plexiglass sides and covers. (Clear sides will not afford the same degree of insulation as solid sided frames.)

A permanent cold frame set to the side of a garden plot can serve as a seed bed and starting place for crops year round. A permanent cold frame can be heavily insulated to provide a growing place in the coldest winter regions. A portable cold frame--usually easily disassembled or small enough to be carried--can be moved around to protect small plantings or beds. A portable frame is highly suitable for mild winter regions and for small gardens--a portable cold frame can be removed from a garden bed, dismantled, and stored when the warm weather arrives.

Cold frames collect solar energy for heat. Because a cold frame is a passive solar collector the sloping top is best positioned to face south, southeast, or southwest in the northern hemisphere. This will allow the maximum sunlight into the frame during winter when the sun tracks lower in the sky. The slope of the top can vary from 35 to 55 degrees. The higher the angle of slope up to 55 degrees the more sunlight will enter the frame during winter. One formula for setting the angle of the top or sash is to add 15 to 20 degrees to the latitude of your garden: thus if you live in Illinois or Pennsylvania on the 40^th parallel, set the sash at 55 to 60 degrees.

The clear or translucent top or cover of the cold frame is called the sash, glazing, or light. The sash can be made of glass or rigid fiberglass, acrylic, Plexiglass, or UV-stabilized polyethylene plastic. Home-made cold frames often use old storm windows (window sashes) for covers. The cover or sash iis usually hinged at the back of the frame for easy raising and lowering and ventilation, but a top can also slide off of the frame. A cold frame top should be easily opened to ventilate the frame--that is allow fresh, cool air into the frame when the outdoor temperature rises. (You can ventilate a frame by simply propping a stick or block under the sash. As well, automatic solar-powered frame openers attached to a thermostat can also raise the top when the inside temperature reaches above 70°F.)

Cold frames commonly open to the planting bed below and can be planted in directly; allow at least 4 to 6 inches of soil for salad crops and more for larger crops. Cold frames also can have sand or gravel bottoms on which pots, containers, and seed flats can be set. Soil, sand, or gravel can be laid over a weed-proof membrane attached around the base of the frame.

Cold frame advantages. A cold frame offers plants the advantage of good outdoor light while protecting them from the cold, rain, snow, wind and hailstones. A cold frame can add 10 to 25 degrees to the outdoor temperature depending on the weather and the type of frame. Even a modest increase in soil and air temperature inside a cold frame can extend the growing season for most vegetables from 4 to 6 weeks both in spring and fall. That means an additional two to three months of edible gardening each year.

Here are things you can accomplish with a simple cold frame--a box with a glass top and the heat of the sunshine:

• Start seeds four to six weeks earlier in the spring than in the open garden (plants in the cold frame are likely to grow somewhat more slowly but will be stronger than those grown in a green house as a result of the bright natural light).

• Protect seedlings and allow them to grow strong and sturdy until they are large enough to be transplanted into the open garden.

• Harden off or acclimatize plants started in a greenhouse or hotbed before transplanting or setting them out into the open garden.

• Grow certain crops to maturity; any crop can grow to maturity in a cold frame as long as the frame is large enough to accommodate the crop and the proper temperature and watering is maintained.

• Root cuttings of perennials.

• Grow cool- and cold-hardy crops such as lettuce, spinach, and other leaf crops late into the fall or through the winter.

• Protect semi-hardy crops planted in the autumn through the winter; for example, cabbage planted in the autumn can be protected by a portable cold frame through the winter and then allowed to mature once spring arrives.

Cold frames in cold winter regions. In very cold winter regions, cold frames can be fitted with insulated sides and set atop insulated foundations to retain more heat. A wooden, block, or cement cold frame can be insulated easily with the addition of 2 or more inches of Styrofoam around the inside of the frame and with a layer of 1½ inches on the bottom under the growing bed. Insulating foam can be easily cut and glued to the inside of the frame. As well foam shutters or mats can be placed atop the frame's clear lid at night--this can increase night air temperature inside the frame by 8°F. A double-paned glass or plastic sash (top) or a sash fitted with an under-layer of 4 to 6 mil plastic sheeting will provide additional insulation of up to 6°F.

A simple way to outfit a cold frame for cold winter regions is to place hay bales or bags of leaves around the outside of the frame. Tarps, woven mats, and old blankets can use used to insulate the top; this additional protection can increase the temperature inside the frame by 6°F at night; that can mean a season extension of 6 to 12 weeks. The inside of a frame can be painted white to reflect sunlight or black to retain heat. Thermal collectors as simple as masonry blocks or jugs of water set against the north wall of a frame will retain solar heat during the day that is released back into the frame at night.

Permanent or portable cold frame? Depending upon the size of your garden, your needs, and the number of months you want to keep the harvest going, you can use a permanent cold frame or a portable cold frame.

A permanent cold frame can be built on a foundation of concrete or block dug into the ground (which will provide increased insulation from winter temperatures) or constructed on the garden surface. A permanent frame can be constructed of heavy wooden planks--2 inch thick by 6 to 8 inches wide, and can be fitted inside with additional insulating materials. A permanent frame is likely to be sturdier and longer lasting than a portable frame and can accommodate a steeper angled sash or light and be likely to withstand a heavier load of sleet or snow without sagging.

A portable frame may be all that is needed in mild winter regions where crops require less protection than in cold winter regions. In mild regions, the portable frame can be shifted from bed to bed or disassembled when not needed. Portable frames can be constructed to fit atop permanent raised beds. Many commercial cold frames are collapsible. Portability in a small garden will allow for greater growing opportunities with limited planting bed space. A portable frame, however, will likely have less insulating capacity than a permanent frame and be subject to wider temperature fluctuations.

To decide between a permanent frame and portable frame consider:

• How and when the frame will be used.

• The climate and severity of winter.

Types of cold frames. As you consider a cold frame for your garden, you will learn about several types. Here are a few common types:

• Double-glass frames. A frame whose sash or light is double glass (or plastic) will offer maximum insulation being 40 to 50 degrees warmer during the day than outside and 25 to 30 degrees warmer at night. The double layer is separated by an insulating space of air.

• Single-span frame and lean-to frame. The single-span and lean-to frame allows the sash to rise at an angle of 40 to 45 degrees against a solid north-facing back wall or panel. The lean-to frame affords the most light to plants when it covers beds running east to west.

• Flat-topped frame. A flat-topped frame can be as simple as a raised bed with a storm window sash or framed plastic sheet set on top to protect seedlings. You can also make a flat-topped frame by placing a rigid clear top on beams set over cinder blocks, brick, or hay bales.

• Tent-style frame. A tent-style cold frame is steeply sloped from a ridge poll with two sash sides. The tent-style frame can be made from framed sheets of acrylic or fiberglass. With high-rising sides the tent-style cold frame is suited for growing large vegetables.

• Double-sash cold frame. A double-sash cold frame offers access into the frame from two sides. The double-sash frame is a tent-like frame with a central hinge joining two sashes. The two sashes are joined at a T-shaped center support that runs the length of the frame. The double-sash frame allows for watering, care, and harvesting from both sides of the frame.

Related Articles:

Cold Frames for Autumn and Winter Crops

Extending the Season: How to Get More Out of Your Garden

Planting the Autumn, Winter, and Spring Garden