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7. Heating, Ventilating, Cooling, and Lighting

Ample light and ventilation are essential in any greenhouse, while heating, humidification, and cooling must be considered in most operations. What you need will depend on where you are located and the crops you grow.

HEATING

There are many types of heating units. Choose one which will keep the temperature of your greenhouse at desired levels for the full 24 hours. With any of the nationally advertised heating systems, spare parts are easily purchased. This is a good feature as it may save you time (and thus money) in case of a breakdown.

Hot Water and Steam Heat

In cold areas, hot water systems using coal, oil, or natural gas are the most popular for greenhouses.

If you have a large enough household heating system, you may be able to pipe hot water into the greenhouse pipes. This 62 furnishes economical heat. But if the greenhouse is very large or is located over 100 feet from the household boiler, it may be better to install a separate system.

Hot water furnishes an even, warm temperature minus the harmful fumes that are produced by some portable-type heat­ers. With a separate hot water system, it is necessary to install a boiler. The boiler can be automatically fired with oil, stoker, or gas, thermostatically controlled, or hand-fired with coal. If it is fired by hand, it should have sufficient capacity to run for 10 or more hours without attention.

Automatic firing and thermostatically controlled tempera­tures are a saving in time and money. They also assure more accurate heating.

I use oil for heating my greenhouse. The system is inside the greenhouse annex. Units burning natural gas can be safely in­stalled directly in the greenhouse or in an open attached unit. If you are using coal, artificial gas, or a mixture of natural and artificial gas, the boiler must be placed in a separate room or building, since fumes from these fuels are detrimental (some­times fatal) to plant life.

The heated water circulates through pipes or fin radiation. I have fin-type radiation. Each foot of fin radiation has several times the radiating surface of a foot of standard pipe, and much less footage is required to maintain desired temperatures. For easy calculation, 1 foot of 2-inch fin-type radiation will equal about 6 feet of standard 2-inch pipe. These figures vary with the size of the fin and the number of fins per foot. The hotter you need to keep your greenhouse, the more pipe or fin sections you should have.

Steam heat, which also utilizes piping or fin radiation, is cheaper to install but it dries out the air and the plants.

21. A hidden row of fluorescent lights and a waterproof tray converted this counter in my study into a beauty spot—and a sales display area— for some handsome gloxinias. (Courtesy, Town Journal)

Oil Heat

A forced-air oil heater is inexpensive. If you need heat in your greenhouse but a few times during the year, one of these fan-type heaters may be just the thing for you. The fan forces a brisk circulation of hot air through ducts running under­neath plant benches.

You can pipe the smoke out through a chimney or through pipes running under the bench and vented out one end of the greenhouse. This pipe surface gives off added heat and removes the necessity of a chimney stack.

Gas Heat

Many owners of profit-making greenhouses live in areas where natural gas is available. A natural gas unit is quite rea­sonable in cost. One low-priced heater is all-aluminum and about 12½inches in diameter and 22 inches high. A somewhat larger heater, 15 inches in diameter and 25 inches high, nat­urally is about double the price. This type of heater is set under the side benches so that heat goes out into the walk. It is vented and piped into the outer gutter or directly outdoors.

These heaters are not recommended for use with fuels such as Butane or Propane.

Electric Heat

Where the cost of electric current is low, it might be feasible for you to heat with electricity. The heating coils are the same as those used for soil-heating cables. These coils are wound around ¾-inch pipe which is run around the inside of the green­house. A thermostat controls the heat.

Automatic Temperature Alarm

An automatic temperature alarm—a thermometer hooked up to a bell—is good crop insurance. An unexpected cold night, failure of electricity, or trouble with your heating sys­tem might cause you to lose an entire crop. So that a power failure will not affect it, the alarm operates on batteries or dry cells. When greenhouse temperature drops below a pre-set mark, the thermometer actuates the bell.

The bell for our greenhouse alarm is placed just outside our bedroom door. Thus we are able to hear it even in the noisiest stormy night.

Emergency Heating

Even the best heating facilities sometimes go wrong, and an alarm system has little value unless you have on hand some emergency heating equipment, ready for use.

My emergency setup consists of two portable electric heaters. I set them on boxes, one at each end of the greenhouse, and place an electric fan behind each of them. Although not recom­mended for daily use, this setup serves the purpose and keeps plants from freezing or chilling and so suffering a setback in growth.

A still simpler from of emergency heating can be provided with a candle inside a flower pot. Light the candle, then invert a similar sized pot over the first one—pot rims together. The candle will receive oxygen through the hole in the top pot. Place several of these heaters around the greenhouse and you will maintain an above-freezing temperature. The number of these units you'll need will depend on the snugness as well as the size of your greenhouse.

OPERATION COSTS

In many sections of the country heat is the most expensive item in greenhouse operation; in other areas it is negligible. Any manufacturer who specializes in greenhouse building will give you accurate estimates of heating costs for your location and greenhouse during an average season. Or a local plumber may advise you. A friend in Michigan who uses a forced-air circulating heater for her seven-section redwood house finds the cost about $35.00 per season to maintain 50-degree tempera­tures at night and 60 during the day. A Minnesota grower, employing hot water for the same sized house, keeps it at 65 at night, 75 in the day, at an estimated cost of $105.00 per season.

VENTILATION

Your plants should reach the market in tip-top shape, which will not happen if your greenhouse is too cold, too warm, or too drafty. So you should pay close attention to ventilation. Automatically controlled (thermostat) ventilators are helpful and relieve you of constant attention. If you don't have them, open the ventilators first thing in the morning if the day is due to be hot—regardless of the calendar. During the summer, I leave the ventilators open all the time. In spring and fall, take care that cold drafts do not blow directly over plants. The best way to ration fresh air is to open the ventilators a crack at a time, thus avoiding sharp declines in the inside temperature.

Ridge or side ventilators, and exhaust fans are available for greenhouses. If you are using side vents, be sure that they are arranged in a way that will not cause the air to blow directly across your plants. Louvered side vents provide excellent serv­ice and can function as part of the summer cooling system you may eventually wish to install. Plants such as cymbidium and cyclamen require rather low temperatures part of the year— another good reason for a cooling system.

The large commercial grower in a huge greenhouse—with his constant personal attention, abundant water supply, and great body of air overhead—can well afford to have an opening in the roof as a means of ventilation. But not so the person with a typically small, low-roofed, hobby greenhouse. Too much air can escape in a short time. And it is not only the hot air that escapes through a roof vent; with it goes the humidity the plants need so very much.

Automatic ventilation, via a fan system, changes the air com­pletely every 3 minutes. With the fan in operation only briefly, your plants benefit from whatever humidity is in the green­house.

You can purchase manual ventilator openers made of metal, or by investing a little more, you can install automatic openers. These are hooked up to thermostats and will open and shut ventilators whenever a change of air is advisable.

HUMIDIFICATION AND COOLING

Evaporative coolers do a wonderful job of both humidifying and cooling. One unit offers controlled cooling and humidify­ing—from a gentle breeze to a full torrent of air at the turn of a three-speed motor switch. At full capacity this unit will change the air in a 14- by 30-foot greenhouse approximately every 2 minutes. Directional air-flow louvers on the fan swing easily into position to control flow to any part of the house to promote draft-free ventilation, cooling, and humidifying.

Most coolers currently on the market are built for eye appeal, as well as service and stability. In one model, heavy-gauge zinc-coated steel cabinets and louvers are primed with rust-resisting zinc chromate and finished in baked-on enamel, while special non-vibrating mountings support the heavy three-speed motor. Evaporating elements are constructed of three remov­able pads of odorless aspen.

LIGHT AND PLANT GROWTH

Green-leaved plants need light to live. Light acting upon leaf and stem cells helps change carbon dioxide taken from the air and moisture from the soil into sugars and starches, necessary elements for plant growth. This manufacturing process is called photosynthesis. To carry on photosynthesis plants must have, in addition to light, proper temperatures and nutrients.

Measuring Light

Light is measured in foot-candles. One foot-candle is "the illumination at all points that are 1 foot from a uniform source of 1 candle-power of light."

22.   Ready-made  fluorescent-lighted  cases  for  propagation  or  growing can be slipped under greenhouse benches, workroom tables, or into any dark, unused spot.   (Courtesy, General Electric Co.)

The intensity of light varies with the seasons. In summer, it may reach 10,000 foot-candles or more during the brightest part of the day. This is too much light for African violets, begonias, and decorative green pot plants. During winter months, light intensity may be reduced to a meager 500 foot-candles. Clouds and smoke from factories also reduce light.

When light intensity becomes too low, plant growth slows almost to a halt, stems become weak, leaves thin, and flowers are paler than under normal conditions. Under too-high light intensity, plants tend to wilt, wither, and may become yellowed or show burned spots.

With optimum conditions such as good soil, correct watering, and proper temperatures, food production in plants is stepped up as they receive more light. To achieve maximum growth and flowering, you must regulate light intensity to make up for sea­sonal changes. Shade your greenhouse during summer to cut down the light;  remove  shade  to  admit more  winter  sun; brighten all dark corners with artificial light.

Artificial Light

Given proper temperature and humidity, many flowering   plants, such as African violets, gloxinias, other gesneriads, and    foliage plants, thrive under artificial light. The addition of fluorescent or incandescent light, or a combination of these, can convert dark, wasted space under benches and on window-less wall areas, as well as in basements and closets, into profitable plant-growing space.

Some greenhouse owners have found that fluorescent light  speeds propagation and flowering of African violets, so they    grow the plants in a combination of natural and artificial light.

Day Length

The growth and flowering of many plants depend on their daily hours of exposure to light—either natural or artificial. Without going into technical detail, this, roughly, is called photoperiodism, a phase of which is called day length. Plants are informally classified into three groups.

1. Dahlias,   delphinium,   pansies,   tuberous  begonias,   and other plants which come into flower more rapidly during the long summer days of maximum light—or under the stimulus of artificial lighting—are called long-day plants.
   
2. Chrysanthemums, gardenias, poinsettias, etc., which start to flower when their light-exposure period goes down, are called short-day plants.
   
3. A third group contains plants—including African violets, carnations, and roses—which are unaffected by day length; these are called indifferent.
   

Science is now trying to determine whether plant growth and flowering are actually governed more by the daily period of uninterrupted darkness than by the length of exposure to light. Thus the plants that are now classed as long-day and short-day eventually may be called short-night and long-night plants.

Lights in the Greenhouse

Whether you extend your growing space by lighting with in-candescents or fluorescents, there are a few points to remember.

1. All lights must have some type of reflector, either home­made or purchased, to concentrate the light down on the plants.

2. Light bulbs and tubes must be spaced at definite distances   to give the plants the correct amount (foot-candles) of light.

3. Lights must be left on long enough to accomplish the job they are intended for

Install fluorescent lights and their reflectors in pairs of 40-watt tubes. One white tube and one daylight tube will give the plants a proper balance of red and blue light rays. Two day­light tubes and two 25-watt incandescent or a multiple of these will also give the proper lighting.

A new type of fluorescent light, called high output, supplies almost double the amount of light given by ordinary fluores­cents. These lights, with special starters, are available on order from major electric companies.

An automatic timer, to switch lights on and off, will be in­valuable as a labor and time saver.

Note that two 40-watt tubes will light an area 2K by 4 feet.

Short-Day Plants

Short-day plants need a specific number of solid hours of darkness to form flower buds. Under natural conditions they will do this as autumn approaches. But there are two ways to change their flowering period. You can hasten it by shading the plants to supply them with extra hours of darkness. Or you can delay flowering by breaking the darkness-induced budding cycle with additional or intermittent light.

Covers of heavy black sateen, plasticized cloth, or building paper can be used to shut out light. This covering is placed over the plants in late afternoon, perhaps 5 o'clock, and left on until 7 o'clock the following morning. Plants requiring such treat­ment should be grown in an area that will accommodate the erection of a wire frame around them to facilitate placement of the shading material.

The time to start shading depends on when you want to sell the plants. Chrysanthemums require 2 to 4 weeks of artificially induced darkness to start flower buds ahead of normal season schedule;  poinsettias  shaded  about 2  weeks  beginning  the first part of October will flower for Christmas sales. Shade the Christmas begonia (Melior) from October 10 to October 20 to make it produce a heavy crop of flowers for Christmas sales.  If you supply short-day plants with 2 to 6 hours of additional I    evening light from 25-watt bulbs spaced 2 feet above the plants, I    you can break and delay their budding cycle. With proper manipulation of light and darkness you can have them in flower through most of the year. Many commercial plant sup­pliers, especially chrysanthemum specialists, furnish exact data for each variety they sell.

You can change and control the flowering periods of such im­portant profit-makers as kalanchoe, poinsettia, gardenia, China aster, and Christmas cactus, by shading or lighting them.

Long-Day Plants

Long-day plants, as a rule, need 14 or more hours of light per day to develop good flowers. In winter when days are short, give these plants 4 to 6 hours of added light. Sixty to 75-watt incandescent, as many as needed, are spaced 3 feet apart andhung about 4 feet above the plants. They will supply the right amount of light.

Asters, dahlias, delphinium, feverfew, some varieties of iris, marigold, pansy, stock, and tuberous begonias are some of the plants which respond favorably to artificial day lengthening.

23. Can you find an unoccupied, non-productive inch of space? Fluores­cent lights make even the end walls of a greenhouse suitable for growing plants.   (Courtesy, General Electric Co.)

ADDITIONAL GROWING SPACE

If you want still more room, add fluorescent light setups to the dark areas of your house and turn them into plant-growing spaces. Basements, attics, closets, windowless walls, utility rooms—all become propagation areas when supplied with fluorescent lighting.

These lights work on ordinary household current. However, before installing more than a pair or two of them it would be wise to check with your electrical company to find out if your present electrical wiring can stand the additional load.

If you need only a small additional propagation area, you may find it advantageous to buy one of the commercial fluores­cent light stands with two to four shelves. A model with three shelves holds two hundred 3-inch pots. There are models avail­able with or without wheels.

PROFIT-MAKERS UNDER LIGHTS

Whether you are using the greenhouse or are growing plants in a special room or area in the home, regular attention is essen­tial to success with artificially lighted plants just as with sun-lighted plants.

Try to keep daytime temperatures between 70 and 75 degrees with the usual 10 degree drop during the night. Increase humidity by setting the pots on moistened pea rock. Grow the plants in sterilized soil. Water them regularly, according to the needs of each plant. Spray plants with insecticide every second week, as a preventive. As plants grow, shift them to the next larger sized pot. Leave the lights on flowering plants 12 to 16 hours each day; 4 to 8 hours per day for foliage plants.

If the plants produce long willowy foliage, they are too far from the lights. Set them on boxes or inverted flower pots to boost them closer. If leaves turn yellow and hug the pot, plants are probably getting too much light. Move them farther from the lights.

With stationary fixtures, aim for 18 inches between light tube and plant table to allow head room for plants in 4-inch pots. If you grow larger plants, fasten the lights a greater distance from the table or, better still, operate them on a pulley so you can regulate distances to suit plants.

As you experiment, you will find the proper distances. Here ' is a rather general rule to guide you. Light-loving plants, such as gloxinias and many other tuberous gesneriads, cacti, coleus, and wax begonias grow best with about 8 inches between light fixture and pot rim. African violets, rex begonias, and episcias, among others, thrive when space is about 11 inches. Foliage plants, philodendron, ivy, and cissus can be set 18 to 24 inches from the source of light.

PROPAGATION UNDER LIGHTS

The most popular plants for propagating under lights are the gesneriads. Leaf cuttings or plant divisions can be rooted by inserting them in your favorite rooting media—vermiculite, peatmoss, sand, sphagnum moss, or a mixture of these. You can speed rooting by putting a transparent plastic "tent" over the pots or flats and placing them about 6 to 8 inches from the lights. Transplant the small plants as they appear, which some­times is but a matter of 3 or 4 weeks.

Tubers and rhizomes can be rooted by placing them on peatmoss, sphagnum moss, or vermiculite. Keep the medium moist and place the planting about 4 to 6 inches from the lights. As soon as sprouts show, transplant the tubers to individual pots.

24. In the big greenhouse of Edna Roberts, York, Maine, supplementary fluorescent lighting puts the lowest bench on a profit-making par with the topmost. Waterproof installation is essential for under-bench units. (Photograph by Genereux)

Start any of the gesneriads from seed by sprinkling the seed over sterilized, milled sphagnum moss, sand, or vermiculite. Cover the planting with a pane of glass or slip it into a trans­parent plastic bag. Seeds will sprout in a dark, warm area (70 to 75 degrees). As soon as you see the green flecks of new plants, place the planting as close as 3 inches from the light tubes. Here the seedlings will grow with amazing rapidity. By careful timing as to fertilizing and transplanting, you can have flowering gloxinias in 3 to 5 months and African violets in 4 to 6 months. (For additional information, see my book on Grow­ing Plants Under Artificial Light.)

PROPAGATION UNDER MIST

Plant physiologists have discovered that a mistlike fog of water keeps tender softwood cuttings (cuttings from new growth) in such excellent shape they "just have to root!" Under these conditions of either constant or intermittent mist the cuttings don't wilt and there is a minimum of trouble from fungus and rot.

There is a mist unit on the market that has been adapted from a larger commercial mist-maker system. It's called the Mistic Bubble and is an excellent greenhouse space stretcher. This is a system for rooting soft cuttings outdoors, in sand under plastic with the use of electronically controlled mist. Harvey M. Templeton, Jr., Winchester, Tennessee, is the inventor of the system and the control known as the Electronic Leaf. With this portable system the plants get water automatically, as they need it, until rooting takes place. Then the temporary green­house cover is gradually removed and the plants are thus hard­ened to growing outside in the full sunlight.

The hemispherical shape of the Mistic Bubble is designed to let in light evenly all around as long as the sun hits the cover. The plastic covering has a pigment cast into it to protect the cuttings from excessive summer heat. The low capacity mist nozzle, using 1½ gallons of water per hour, keeps the leaves of the cuttings wet at all times, promoting very rapid rooting.

The Mistic Bubble is 4 feet in diameter and has 12½ square feet of planting space—it will hold 1000 cuttings at a time. After they root the cuttings can be sold or planted out to grow to maturity. In the South, the Bubble can be used throughout the year.

We are installing one of these units to use for propagation of herbaceous plants and conifer cuttings, which we will plant out as a basis of a profit-making nursery. We'll start by lining out several hundred daylilies and iris plus a few rows of evergreens. Later we may include chrysanthemums (these too can be rooted in the Mistic Bubble), and a few Azalea mollis, the hardy species, which several dealers now carry and which can stand our hard Minnesota winters.

I have described this system not only because I've had ex­perience with it but also because its basic principles apply gen­erally to mist propagation in the greenhouse as well as in a purchased or homemade propagating case. Fog nozzles for water lines are available for those who wish to make their own setups. Complete mist propagation kits are on the market too.

BASEMENT PROFITS

A husband and wife living in Wisconsin have converted their entire basement into a fluorescent lighted area for African violets. The floor has been tiled with asphalt. Counters and fluorescent lighted showcases have been added to increase cus­tomer appeal. In this basement "greenhouse," they strive to grow only the varieties of violets in greatest demand, and their customers come from hundreds of miles to purchase cuttings and small plants. They do no mail-order selling, but make a good steady profit from their over-the-counter sales.

25. The vigorous condition of these African violets is proof of the ideal light that well-arranged fluorescent, incandescent setups provide. Wasted cellar space is thus made profitable. (Photograph by Manning Bros.)

A grower in Winterset, Iowa, earned enough money from the sale of light-grown house plants to pay for her greenhouse. Her specialty is African violets. Another Iowa grower, who grows violets under basement fluorescents makes enough profit from them to pay for all of her own clothing and that of two high-school-age sons.

A Missouri "amateur-commercial" grower, the wife of a retired physician, adds a substantial amount to his retirement pay through sales of violets grown under light in a basement and two upstairs bedrooms.

A pair of fluorescents placed under the shelf in my green­house annex give me considerable extra room for starting gloxinera seedlings and cuttings.

Since we have no basement in our home, we have installed lights in our utility room and in my study. Under these setups are started many of the gloxinias, African violets, episcias, and various hybrid seedlings destined for sale.

Turn Your Basement into a Plant Room

A basement setup can be constructed by fastening one or more pairs of fluorescent tubes to a sheet of plywood and sus­pending it from the ceiling by chains or ropes. Enamel the ply­wood white to give increased reflection, and if the basement walls are dark, give them a coat of whitewash or paint. A table or counter to hold the plants should be centered about 18 inches under the light tubes. This distance will prove satisfac­tory for growing a number of plants. Those needing most light can be boosted up with boxes or inverted flower pots while the leaves of taller plants such as potted lemons or other citrus, hibiscus, and holly, among others, should just clear the light tubes.

If you don't want to give over this much home space to plants, you may be able to fasten lights inside an old cabinet or chest and grow or propagate plants in it.

Then there are plant-growing cabinets, mostly of metal, with lights installed in them. These can be purchased directly from the manufacturer and are advertised in most of the leading garden magazines.

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