How to Make a Greenhouse

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How to Make a Greenhouse

Traditionally defined as any glabuilding or adjoining structure wh( :ontain plants, today's greenhouse_ ariety of sizes, shapes and compositions.

There are several advantages that all-year gardening greenhouses afford. Summer and fall crops yields can be stretched one season longer often through the otherwise deadly winter season. Gardeners also use their greenhouses to gain a head start on springtime planting.

Another important plus to greenhouse gardening comes with the opportunity to con-rowing environment. Frosts, blizzards,:s. heat waves, and other weathercan be virtually ignored behind thert of greenhouse windows and walls.IFitirrter, there is the therapeutic value ofgardening. Tending fresh fruits, vegetables and ornamental flowers throughout the year is considered by many doctors to be a tranquilizer for daily stress and work tension.

Greenhouses today fall into several generalattached (units adjoining the house,window box, basement, patio, or sun-porched greenhouses) or freestanding (full-sized units separate from the house, either above or partially below grade).

The Attached Greenhouse: The gardener seeking to minimize construction and mainte-nses, and possibly even capture some heat forthe house, may find that an attached greenhouse is more suitable than a freestanding be most effective, a south wall of thecould be chosen for this type of greenhouse. The spot should not be heavily shaded by trees or other buildings, but it should be protected from strong winds that could chill the greenhouse and possibly weaken it structurally. Greenhouse designers and builders agree that the most efficient use of space andsolar heat gain can be obtained by making thelength of an attached house about twice asgreat as its width.

Supplemental heating can be minimized—or eliminated entirely—by taking advantage of some features that are being incorporated into new solar and energy-efficient houses, namely,the use of multiple-layer glazing; nighttime insulating shutters, curtains and shades; and the addition of thermal mass, such as concrete,stone, or brick floors and house walls and warer- or rock-filled containers to store solar heat during the night and on cloudy days.

A truly efficient attached greenhouse can actually provide heat for the house in winter. Vents near the floor allow cool house air to enter the greenhouse, where it is warmed and then circulated back into the house by means of another vent near the ceiling of the greenhouse. Since warm air naturally rises, no fan is necessary in many instances to move this air. Such venting not only helps to warm the house, but it also permits good air glow throughout the greenhouse, raises the humidity of the house and distributes plant-loving carbon dioxide from the house to the greenhouse. Of course, vents to the house should be closed during the summer months, and vents from the greenhouse to the outdoors should be opened during this time so that neither the house nor the greenhouse gets overheated.

Although space in the attached greenhouse id limited by theupright building wall, every inch can be put to work by the use of plant benches, ground beds, eave shelves, ledges, and hanging baskets. The straight-sided leab-to makes it possible to grow tall plants close to the glass. Straight sides accommodate eave shelves better too, and they provide better ventilation and temperature control. The straight-sided houses are somewhat mre expensive, however, because there is more glass area. On the other hand, slanting sides capture more sunshine.

Window greenhouse: This variety is one of several "mini-greenhouses" designed to produce healthy flowers and herbs at a low cost. Window greenhouses are also used for starting seed in winter and spring before transplanting into the outdoor garden.

Almost any window opening into the house can be use for these small conservatories attached to a windowsill abd framing. For gardeners planning to use th ewindow greenhouse year-round, a southeat-facing window is recommended. This direction will obtain ample sunlight even in winter. Small heating units which fit into the window extension, or heating cables, may be used to keep the greenhouse sufficiently warm, and insulating shutters or shades can be pulled over the glass at night.

Galvanized trays one inch deep are recommended for the window unit. These trays can be filled with gravek abd kept moist in order ti maintain adequate humidity.

Basement greenhouse: From the outside a basement greenhouse looks like a sloping cold frame built against the foundation. Inside, it is an alcove in the cellar wall, and a concrete floor raised above the basebent floor. Like the foundation, it is built of concrete blocks.

The floor should be at least 3.5 feet above the basement floor because of the sharp angle fof the midwinter sun. The foundation wall in front should be about two inches higher than the greenhouse floor to prevent water from running out on the cellar floor to prevent water from running out on the cellar floor. This crete cap that makes an attractice shelf of parapet for displaying plants in the foreground.

A shelf placed beneat the glass at one end is used for sun-loving plants and can be duplicated at the other ened. The greenhouse should face south, southeat or southweat. With only one hot air vent in the basement, the tem[erature should stay between 55 and 60 °F/ (12.78 and 15.56 °C).

The Freestanding Greenhouse: To many people, the freestandinggreenhouses offer distinct advantages.Although their typically all-glass composition often translates into a 25 percentating bills, and they require extra ex-for wire and pipes, the estimatedaddition of plant-growing space-hed greenhouses \is ample compensation. Other advantages are that most of thesegreenhouses can catch sunlight from everydirection, and they are more adaptable forground beds. The more energy-efficient free-standing greenhouses have north walls built into a hillside or have floors which .'tire a fewfeet below ground level. Many people refer tothese as pit greenhouses.

The pit-type house, except for sever sub-zero (F.) weather, is sun heated. The onlyadditional heat needed under conditions of ex-treme cold is usually a 200-watt electric lightbulb or a small electric heater. Temperaturesin the pit-type house make daily watering un-necessary. Usually only the south side is glassedin, and this is set at a 45-degree angle to admitthe most sunshine. Ordinary hotbed sashescan be used.

To add warmth to the pit house, the endsand unglassed side should be double walledwith about 31/2 inches of insulating materialbetween. Doors and ventilators should alsobe insulated. After sunset, the glassed areasshould be covered with padding or anotherinsulated covering. When pads are used tocover the sashes, tarpaulins are rolled downover them to keep them dry. Wet paddingmakes poor insulation.

The Dutch door is best for the pit housebecause the upper half can be opened forventilation during the winter. The door shouldbe at the east end of the house to be betterprotected from prevailing cold westerly winds.A ventilating window can be placed at the westend. This is most important in the pit green-house. It should be open during the warmesthours of every day. Some pit houses use sky-light openings on the top of the unglassed sidefor ventilation.

Location: Choosing the best greenhousesite is an important step requiring severalconsiderations. Convenience, accessibility,yard space, and general land conditions arevariables to consider. Attached greenhousesenable the gardener to enter the greenhousequickly and easily through adjoining, enclosedentrances. They best suit gardeners with little yard space, but with sunlit base—windows and sills suitable for ahouse "box," or enclosed porches. Fing greenhouses should be locate:.spacious environments, and where :-exposed to ample sunlight.

Exposure to sunlight is ansideration. All greenhouses should belso that the maximum dosage of 91utilized, especially in winter whenneeded. A three-hour exposure of anconsidered the minimum daily require.most plants during winter.

Contrary to popular belief, the precise direction in which a greenhouse faces isnot a crucial consideration. If the mril!east and west, plants on the greenhouse's north side may get more shade, but this isashortcoming. Many plants thrive car itSome plants in attached greenhouses grow best in a southern, southeastern orexposure, in that order. Western elprovide ample sunlight but lack the shade needed in summer.

A more important considerationrection of prevailing winds. Hinged doors of the home greenhouse should alwaysaway from the wind, rather than into itwise, strong gusts will knock them down.

Construction Materials: Once the style and location of your future greenhoubeen selected, construction materials :chosen. Gardeners can select from m,plastic, fiberglass and glass materials.

Above ground: Prefabricatedhouses are usually about nine, ten orwide. Lengths are in sash sections of al*feet, so the greenhouses can be built nlength. They come with slanted orsides. These greenhouses are made ipanels that can be put together with adriver, wrench and hammer. All the parts are furnished, cut to fit in place. The glass is cut to size and is not putty glazed. It goes into glass grooves inthe sash and is held weathertight with a special caulking rope.

While the prices for the materials for a prefabricated greenhouse are higher than parts such as glazing bars, sills, eaves, ridge and fittings of a conventional-type greenhouse, the time they save in labor greatly offsets differentce.

Greenhouses with polyethylene film or plastic instead of glass are becoming popular for rasons of economy. They are light, so require less rigid supports, but they can rip in heavy winds and the constant exposure to strong sunlight causes trhem to deteriote in a short as six months. Thin flexible films are best used as inner glazing only under thicker plastics or glass.

Fiberglass is another pppular alternative in greenhouse construction. It is sturdy and transparent material, especially when coated with Tedlar. Fiberglass also makes a good heat nsulator, retaining up to 70.8 times more hat than polyethylene film and some plastics,. Fiberglass houses provide natural shade, even during intense sun exposure. Fiberglass has its shortcomings as well, however. It is highlt flammable and often wears down, reducing light transmission and increasing dust and don't break as easily.

Rigid acrylics come closest to resembling glass, but they are easier to work with because they are five times lighter than glass and don't break easily.

Glass has a tendency to turn brittle and crack, and while it is good-looking and clean, it is a difficult material for do-it-yourselfers to work with.

Foundation: The walls below the sills ofthe greenhouse are the hardest part to build.Masonry walls are best because they are morepermanent than those of wood. They also offersome thermal mass for heat retention. Pouredconcrete, brick, cut stone, or cinder blocksmay be used. Cinder blocks provide the easi-est means of building a wall. For appear-ance's sake, the outside can be coated withstucco and painted. The attractiveness of agreenhouse depends a great deal upon its walls,for this is the largest solid area.

If you live in the northern United States,the walls of a prefabricated greenhouse shouldextend below the freezing line. This would beabout 21/2 feet in most areas but may be lessin the southern states and more in the farNorth. The footings below the ground can beof poured concrete and gravel. A conventional-type greenhouse is built with steel posts set onfootings and encased in piers that extend belowgrade. The side walls need only go down tosolid ground, a few inches below the grade.

After the greenhouse has been selected,located and constructed, the continual task ofgreenhouse management begins. Managing thegreenhouse can be divided into two categories:controlling of the greenhouse climate andhandling of the plants.

Heating and Cooling: The key to controlling the climate indoors is regulating theas easily. temperature to simulate the outdoors. Heartierilass has a tendency to turn brittle and plants grow best when temperatures tend to-and while it is good-looking when clean, ward cool. In excessively warm environments, greenhouse plants grow rapidly, but become vulnerable to mildew and insect infestation.

In areas that seldom get colder than 20°F.( — 6.67°C.), more traditional greenhouses mayneed only an electric heater. The heater isinexpensive and can come equipped with anautomatic thermostat to turn on the heatingelement and fan.

For colder environments, gas or hot-waterheating systems arc necessary in traditionalgreenhouses. A no-vent gas unit for heating ishighly recommended by many gardeners, sinceit creates no noxious fumes and costs a fewhundred dollars. Coal or wood-burning fur-naces can also be used to heat greenhouses.

Some suggestions for conserving fuel in-clude keeping the greenhouse as airtight aspossible; using two outside doors and havingone serve as a storm door; using mulch to in-sulate and retain heat; installing heavy-gaugealuminum foil between the heat source and theoutside wall to reflect and retain heat; andplanting a windbreak of trees and shrubs nearbyto retain heat and protect against wind turbu-lence.

The most important companion to anygreenhouse heating system is ventilation. With-out fans to circulate air, the greenhouse tem-perature can vary from 45°F. (7.22°C.) on the ground, to over 90°F. (32.22°C.) nearby..in winter. Mount the fan so that itaway from the heat source to the fic)2.sides of the greenhouse. This way, warmer air will mix with cool air and pick upmoisture in the process. Proper air ciris an important safeguard against plantand infections, since it reduces excesssation, fungus and mildew buildup.

Never build a greenhouse too sir: -a small area, it is impossible to mair-even temperature and a healthy atmccondition. On sunny days, even in thethe temperature in a four-by-six-foot EAT.house would run over 100°F. (37.78a matter of a few minutes. Thenwhen the sun goes down, it would coo:as rapidly. Plants will not grow unde.-conditions.

There are several ways to savewhen planning your home greenhotstalling shelf hangers on sash bars crends is one space saver. Double-deck =taiwork well for greenhouses containingthree benches, where the upper deckmiddle bench. Shade-loving plantscoleus, begonias and impatiens grow well under these decks or under any benchesgreenhouse.

Shade must be provided duringmonths in the greenhouse, in order toplants which cannot be set outside. Bamboo or slatted matting may be spread over tieor the glass may be whitewashed. By-most of the whitewash will have flaked rt.the balance can be removed with a brush.

Finally, maintain a humid atmosgreenhouse plants. Relative humiditybe about 60 percent. Excessive humidity invites plant diseases and decreased fruit and flower production. Insufficient humidity in the greenhouse hastens development of flowers and fruit at the expense of leaf growth. To increase humidity, tge gardener can install mist syetems, plastic sheets or glass panes over seed flats or benches.

Handling of Greenhouse Plants: In caring for your plants, try to simulate all conditions favorable to the plants growth and development needs. If this demands a period of rest in the garden, a perios should be allowed in the greenhouse. Sun, shade and soil requirements outdoors should be duplicated as much as possible in the greenhouse.

Soil. Concocting the proper soil mixtures is another important requirement for the suc-cessful greenhouse gardener. Good soil is aninvestment in the well-being of greenhousecrops, and it should be well fertilized and cul-tivated for that reason. Rich topsoil with livingorganisms, dead organic matter and a poroustexture is best for hardy plant growth. Medium-texture soils, rather than fine or coarse compo-sitions, are best for holding moisture, air andsoil nutrients. Adding organic matter to sandysoils improves water and mineral retention, aswell as helping loosen clay soils.

For most greenhouses, a loam soil isrecommended, because of its good drainageand aeration. Greenhouse soils today are oftenmixes, high in organic matter content. A goodmix for bench or potted plants is two partstopsoil, one part sphagnum peat moss and onepart sand or horticultural perlite. Anothercommon soil mixture is one part soil, one partpeat moss and one part vermiculite, coarsesand or perlite. Whichever soil mixture is se-lected, it always should be kept fairly moist, inorder to sustain the living organisms inside.

Many fertilizers and additives offer vitalnutrition to organic matter in greenhouse soils.Poultry and rabbit manures are packed withnitrogen, phosphorus and humus. Both areapplied at the rate of eight to ten poundsper 100 square feet of bench planting space.Sheep, cow and horse manures are organicfertilizers which add humus and make goodsoil conditioners.

Bone meal is a slow-releasing plant fertil-izer. The steamed variety breaks down quickerfor plant nutrition than raw bone meal.

Lime and wood ashes help neutralizehighly acidic soils. Sawdust and wood chipscomplement successful potted plant propaga-tion. The chips repel snails and provide good drainage.

Peat moss, which puts humus into thesoil and holds nutrients particularly well,makes a fine soil conditioner, rather than afertilizer. Moisten peat thoroughly before mix-ing into the soil. (Dry peat often resists waterabsorption.)

Gypsum conditions and alkalizes green-house soils. It also offers calcium to plantsand indirectly to gardeners who harvest andeat them.

Vermiculite and perlite lighten dense soil and help start plant cuttings or seed. Fertilizers and plant nuytrients are added after roots are established in either medium.

The salt concentration and pH level of soils must be watched carefully in the greenhouse. the state agricultural extension service will check field soil for high salt or pH levels, which can damage plant roots, cause wilting, or slow plant cutting or seedling growth. Loosening the soul and thorough watering help dissolve high concentrations.

Watering: Greenhouse garders should be watered in the mornings of sunny days. Water should be supplied sparinglyto minimize the dangers of fungusWatering should be thorough, butAuld be permitted to show signs ofare watering is repeated. Wateringe should be withheld, if possible, in cloudy weather, since these conditions make evaporation slow. and fungus spores cannot be destroyed as well as they can by hot sun rays.

Here are still more tips on proper watering in the greenhouse:

1. Try to avoid ice-cold water. Room temperature water is preferred by most greenhouse plants.

2. Water can run freely over the bench or tub, but be sure that roots are not left soaking.

3.Keep soil loose for good drainage. Or-ganic matter and sandy loam make the soilhealthy and properly drained.

4.Water plants less in winter, especiallythose that go into dormancy during coolweather. Their need for water decreases atthese times.

5. Avoid water softened with a commer-cial water softener. This water contains chemi-cals harmful to plants. Flushing salty or hardwater usually prevents salt buildup.

Insect and disease control: In handlingplant life in the greenhouse, special care and attention must be given to prevention of pestand disease infestation. Insects and diseaseswhich commonly plague greenhouse crops areeasy to control through the use of good-quality,clean seed and plants, in addition to the main-tenance of an overall sanitary growing environ-ment. Insects, bacteria, viruses, and fungiwhich thrive in "hothouse climates" can bebattled by following these simple sanitation tips:

1.Remove diseased and dead plants; keepthem far from the greenhouse.

2.Prevent wild weed growth near thegreenhouse. Such growth attracts insects andpromotes disease.

3.Keep the greenhouse neat and free ofplant clutter.

4.Be certain that new plants introducedinto the greenhouse don't harbor new germsand pests.

5.Start seed, roots and cuttings in soillessmediums. Sterile perlite, vermiculite and peatmoss are commended for controlling seedlingand cutting diseases.

6.Provide proper greenhouse ventilation.

7. Finally, avoid soaking foliage whenwatering. Also avoid overwatering or overfer-tilizing greenhouse plants.

The organic greenhouse gardener can turnto several safe insect controls, dusts and spraysfor disease outbreaks, especially those in thebeginning stages. Commercially available con-trols include sabadilla, rotenone, pyrethrum,and nicotine sulfate. Many gardeners developtheir own recipes for homemade pest or diseasecontrol.

Not all greenhouse or garden insects areenemies to the propagation of healthy plants,however. Ladybugs, praying mantis, lacewings,spiders, and horse hair snakes are among themany winged or crawling "comrades" in the garden who eat harmful insects.

If helpful insects are not ecompanion herbs in the greenho*tansy, sage and rosemary, mints, b> se_valerian, marigolds, and pyretliriumcomposted soil or plentiful hunnus_ amiriremoval of rotting leaves and Plains-help in the battle against plant 6scomm,pests.

Cool Greenhouse: Since :fuel :tically doubles with every five-dewin temperature, a cool greenhouse Ir.:temperature of 50°F. (10°C.) is beg tiegardener. Plants needing higher :eitmlncan be grown in the cool greenhouse r: mirrtrplaced high on shelves where itdegrees warmer. Practically all tieannuals and perennials do well 4 ike:greenhouse: asters, pansies, stock.sweet peas, marguerites, chry-winter-flowering marigolds, caleruirrms,sum, candytuft, schizanthus, snapdragons, Boston yellow daisies—the list is endless.

Hanging-basket plants like ova",ture ivy, browallia, strawberry begonia.fuchsia, and periwinkle grow well :ra. rerately cool greenhouse.

In cool temperature and organic soil, bulbs such as tulips, Dutch Iris, Lilies, Daffofils, Hyacinths, Ranunculus, and Anemones are easy to grow and give fine blooms. Lettuce, radishes, Swiss chard, kale, and scalliosns dfo very well as do carrots, cauliflower, peas, red and green cabbage, and beets, if you have the extra space they require. Many herbs thrive in the cool greenhouse. A few pots or boxes of rue, sage, mint, marjoram, parsley, chives, and the like will provide garnishes for winter meals.

One of the most profitable ways Vita cool greenhouse is to raise plants fa.-planting in the summer garden. The' =lir the thousands in a home greenhouse.'lants for cabbage, cauliflower, lettuce, broccoli and celery, as well as all of the bed-ants for the flower garden are commonlyred. Seed is inexpensive and the plants are finer than those on sale. Also, they can be raised strains not available on the market.

Farm Greenhouse: While it costs almost twice as much to bring the home greenhouse up to moderate or warm temperatures inLrison with a cool house, many excitingcan be grown that make it worthwhile. Orchids are among them. With a collection:o 75 plants of different varieties, it iske to have something in bloom everythe year. Cymbidiums will keep as long as three months. Any orchidist will tell youants are not difficult to grow. In fact,mill stand more abuse than most of the annuals. Insects are not a serious problem. Orchids can be grown in greenhouse where it is possible to maintain even temperature and keep the atmophere fresh and healthy. High humidity is:al and this is usually provided by placing a tray of coke underneath slat plantLes. This coke holds tremendous quanti-at moisture and gives it off slowly.

Other flowers and plants that do well inmoderate to warm greenhouse include amaryllis, azaleas, begonias, ferns and tropical foliage plants, bougainvillea, cactus, gardenias,7.:as, poinsettias, potted roses, Saintpaulia,antana. Tomatoes, cucumbers and melons can also be grown in the warm greenhouse where temperatures are at least 60°F.:6:C.) at night. Those who enjoy grow-musual things will include such plants as Tacca Chantrieri, the devil flower, Columnea:sa with its fleshy leaves on long trailingthat make it excellent for hanging baskets, and Rondeletia odorata that blooms more or less continually with bright coral red flowers.

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