There are many designs by which to control the environment of those plants one might desire to grow. One of the most economical, commonly adopted by commercial growers and fabricated by backyard hobbyist as myself "huh", is the cold frame or hoop house.
The location of the structure should be convenient to importation of
soil, supplies, the exportation of finished plants. At mid day, rays of
the sun should permeate the entirety of the rows of containers, insuring
consistent growth of each plant. This usually requires a north south
position.
It would be ideal if the floor were concrete sloped to floor drains every 10 or 12 feet, but this sub floor is 2 inches of gravel sloped to drains covered by a ground cover fabric. This floor is about 10 years old and still in good shape. Doors and sidewalks wide enough to accommodate a garden buggy work wonderfully to bring soil, supplies, and plants in and out.
In a cold frame such as this without artificial heat, the most a gardener could hope to achieve on an average year in the southern U.S. would be one zone difference, and in a cold winter, probably half a zone. This house is in 9a but we have 8b temperatures in winter, therefore I hope to achieve 9b temperatures. The covered area of this house is 30' x 30' and on really cold nights I break out the crawfish burner and manage to keep things from freezing. Keeping the house above 50 degrees for the 3 months of winter here in Louisiana would cost entirely too much. I've a ceiling fan top center and run it when the house is closed to circulate air in and around each leaf of the plants.
Poly coverings can be purchased at local home centers as visqueen or online as overwintering or 3 year 6 mill covering. The end walls are more labor intensive and are sometimes finished with a more permanent polycarbonate material, should one become a more serious gardener. In hot climates roll up sides are an advantage because of the sometimes intense heat reducing a greenhouse to an inhospitable place for man or plant.
Shade cloth can be added allowing varying degrees of light penetration for shade loving plants. This shade cloth is a real comfort for the gardener that visits his plants in the heat of summer days, and also allows relief to the plant foliage from the harshness of the heat magnification of the greenhouse film. Tall plants in closer contact to the poly film may show heat stress quickly as the temperature quickly rises in the upper reaches. Good ventilation is mandatory in a greenhouse.
Remember by closing the house to conserve heat, one is at the exact same time, creating an ideal environment for pests and disease, which during the coldest weeks of winter are looking for such a warm cozy place, and often as big a problem as the cold. The worst nightmare of pests and disease is air movement, consistent air temperature, good drainage, low humidity near the floor of the greenhouse, and a gardener that looks at each plant thoroughly, including the undersides of leaves especially those that haven't been checked in two days.
Spray bottles with an insecticidal soap and fungicide should be handy. Fans work well when it's cold and the house is closed up, but when the temperature allows, the house should be opened to allow the natural air currents to purge its air space. Remember that greenhouses are experimental representations, a very small vision, by the human intellect. While you ponder the day to day problems that arise in this tiny environment, keep in mind that it is unnatural, the world outside over rules and you must have a good understanding of it...
Imagine a world as you would have it in your greenhouse. Approach the idea with the humility of a young child, believe that love in its wholeness lives in what knowledge you might find. The far ranging beauty may be yours.
Imagine a world as you would have it in your greenhouse. Approach the idea with the humility of a young child, believe that love in its wholeness lives in what knowledge you might find. The far ranging beauty may be yours.
