It’s December, and the azaleas you selected for forcing in late summer are in full flower, vibrant against snow outdoors. Or it’s a special anniversary, and the roses you programmed weeks ago are blooming on schedule, ready for cutting as a gift. Or at any time of year, the fat yellow football mums you have coaxed along, one to a plant, are the biggest, most beautiful you have ever seen.
Such triumphs—the flower out of season, the spectacular blossom, the bloom timed for a special event—are the rewards awaiting the greenhouse gardener. Some people think that the greenhouse itself brings this magic capacity to control bloom. To a certain extent it does, for its light and warmth will influence the size and timing of blossoms. But for precise control—making flowers appear on a specific date, big or little, singly or in multiples—a number of different techniques must be employed to induce a plant to do what it would not do naturally. Variations in temperature—not just extra warmth, but periods of cold as well—have an effect. Certain chemicals or the regulation of nutrients can stimulate or inhibit blossoming. Artificial light or dark can reset a plant’s calendar to make it bloom out of season. And pinching—removing parts of a plant by squeezing them off between your thumb and forefinger—can delay bloom, increase or decrease flower size, and change plant shape.
Some of these techniques are so old they were presumably employed by the men who tended the Hanging Gardens of Babylon. Others are the result of 20th Century research that is painstakingly unraveling the mysteries of plant growth.
Most involve only relatively simple adjustments to ordinary practice. The simplest, perhaps, depends on the choice of a variety and the time to start it.
Much of a plant’s performance—its size, shape and time of bloom—depends on its heritage. Therefore, one of the most important things a greenhouse gardener can do in his quest for perfect blooms at the right time is to know the capabilities of his plants. If a rose grower seeks to produce long-stemmed roses under glass, he should seek out a hybrid tea variety such as Cara Mia or Carina that will give him that characteristic under greenhouse conditions. For more flowers on a small bush, he might choose a modern floribunda like Mary DeVor with its profuse tea-rose-shaped flowers blooming continuously as an evergreen bush.
A greenhouse is brightened in midwinter by pots of calceolaria, the pocket book flower. Normally April-to-May it was brought into bloom out of its normal season with a 50 ° night temperature.
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A PALACE OF CRYSTAL
Perhaps the most famous greenhouse of all time was built not for plants but to display the mechanical achievements of the Victorian age, it was the Crystal Palace, designed by Sirfoseph Paxton for the Great Exhibition of 1851 in London. Paxton was head gardener for the Duke of Devonshire, and his proposal for an all- glass exhibition hall, covering four times the area of St. Peter’s in Rome, was based on the many large greenhouses he had built. Because there was widespread dissatisfaction with the clumsy, conventional design of the official architects, Paxton’s plan was adopted. The open, light structure of cast iron and glass enclosing such a huge space made the Palace itself one of the marvels of the Exhibition.
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The choice of a variety influences not only the shape of the plant and the size of its blossoms but also the date you can expect flowers. There are Carefree Bright Pink geraniums that blossom 19 weeks after their seeds are planted, and Sprinter Salmon geraniums that blossom after 15 weeks. This variation occurs outdoors as well as under glass, of course, but there the season determines planting time. Inside the greenhouse you have another option— you can, in many cases, choose your planting time. If you want snap dragons for Christmas, plant the seeds in August; if you want them for St. Valentine’s Day, plant them in September.
Once you have chosen the plants and they are growing, your ability to exercise close control over the general conditions in the greenhouse enables you to speed up or slow down the normal pattern of their growth. Adjustments in moisture and nutrients are fairly simple. So are variations in temperature— you simply regulate artificial heat or move the plant to a part of the greenhouse that is warmer or cooler than average.
In general, growth speeds up when plants are given warmer temperatures than they naturally require, and slows down at cooler temperatures. You can gauge how much extra warmth to provide by knowing the climate in which the plant originated. Accelerated growth can be used to advantage in hastening a bud into bloom, but it can be a disadvantage if it stimulates a plant to grow rapidly but produce weak stems and unattractive flowers. Once the plant blooms, high temperature will shorten the duration of bloom; a tulip that might last two weeks at 55 degrees will quickly fade at 85°.
THE NEED FOR COOL NIGHTS
People unfamiliar with the process of making plants flower out of season may think a greenhouse is used to provide a warm place for plants in winter, not just above freezing but really warm. For many plants, warm temperatures do more harm than good. Plants manufacture most of their food with the help of sunlight during the day, but they do most of their growing at night. That makes night temperature critical, which is fortunate, since night temperature is more readily controlled than day temperature. In winter, when days are short and the sun’s rays are weak, plants don’t produce as much food as in summer. If they are exposed to summer-like night temperatures, which push the plant to grow, they are forced to draw on food reserves. The result can be weak, spindly plants and, during flowering, blooms that deteriorate rapidly. Cool night temperatures, under 50°, are a way to hold many plants in good condition in the greenhouse, to delay bloom and to prolong bloom.
FORCING BY CHILLING
Not just cool temperatures but actual cold is necessary to reschedule flowering in some cases. Many plants require a dormant period at temperatures below 45° (but above freezing) before they blossom once more. If you want to get them to bloom out of season, you must give them the cold dormancy out of season, then bring them into the artificial warmth of the greenhouse. To the plants, winter has come and gone and spring has arrived.
Bulbs are often coaxed into flower by such chilling and warming. Flowering hyacinths, daffodils, tulips, crocuses and other hardy bulbs are splendid additions to a winter greenhouse. They can create spring while it’s still January outside. To prepare such a treat, plant the bulbs in the fall in commercial potting soil, water thoroughly, then place them in a cold frame for 12 to 15 weeks. During this time, roots will be forming. The temperature should be kept as close to 40° as possible; it should not drop below freezing. For the most robust blooms, be patient and wait for a strong root system to develop before you move the bulbs into the greenhouse. Then place the pots in a part of the greenhouse where the tempera ture can be kept between 50° and 55°. Shade the plants from direct sunlight for about a week while they become acclimated to the new location. When plants are 4 to 6 inches tall, move the pots into the sunlight, but when the flower buds show color, move them back into indirect sunlight to make the blossoms last.
REFRIGERATING BULBS
In the North, a nearby cold frame is the most convenient place to tuck hardy bulbs for chilling before they are forced into bloom, but any place where they can be exposed to temperatures below 45 degrees but not below freezing will do. Many people use the kitchen refrigerator. One gardener plants the bulbs in small flower pots to keep them upright on the refrigerator shelves, and sets the temperature at 45°. As for giving up the refrigerator space to the bulbs, she says, “I would no more think of facing winter without flowers than I would without food. I always plan to have at least two dozen hyacinths and crocuses in bloom to feast my eyes on in January.” At a few nurseries you can buy bulbs that have already been given a cold treatment, but they must be planted immediately after purchase or the effect is lost.
There are any number of other plants that are easy to force into bloom out of season if they are kept in low temperature—35 to 45 degrees—at night. Azaleas , for example, can be kept out of doors in summer, placed in a cold frame, then moved into the greenhouse at intervals from November on to provide a succession of bloom through the winter.
Nutrition of a plant has varied effects. If you are very generous with fertilizer and moisture, you will get big, bushy plants with heavy foliage, but you may delay flowering or, in some plants, hide the flowers with leaves. Other plants, roses and chrysanthemums among them, respond by producing larger flowers if they are fed the maximum amount recommended on the label of a standard house-plant fertilizer.
EFFECT OF LIGHT AND DARK
Nutrition, temperature and plant selection generally cause only slight modification in flowering times. A much more powerful tool in getting certain plants to blossom exactly when you want them to is light. Its importance to plants is obvious, yet only about a half century has passed since scientists discovered that many plants respond precisely to the number of hours of light and dark that they receive each day—and then the researchers initially drew the wrong conclusion.
When this phenomenon, now called photoperiodism, was first discovered, scientists believed that the length of the daylight period was responsible for flowering, so a number of different plants were studied under controlled conditions and were placed in the following general categories:
• Short-day plants, which bloom when daylight lasts 10 to 12 hours, but won’t bloom with longer periods of light.
• Long-day plants, which bloom when daylight lasts 14 hours or more, but won’t bloom with shorter periods of light.
• Intermediate plants, which bloom somewhere between the extremes, with 12 to 14 hours of light, but won’t bloom with either shorter or longer periods of light.
• Day-neutral plants, which obligingly bloom during short, inter mediate or long days.
These findings were of enormous value to commercial growers, who used them to produce flowers for all seasons and at specific times—poinsettias for Christmas, cut flowers all through the year. Then the nurserymen began to report that plant responses to the length of the day were not always as predicted. More research demonstrated that the classification by day length was a mistake. It was not the hours of daylight but the hours of darkness—the length of the night—that governed flowering. Adding light in the middle of the night could keep a plant from blooming, but adding darkness during the day had no effect on it.
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MAKING AN ORCHID BENCH
1. A stepped bench, which displays many plants in a compact space and allows the constant air circulation needed by orchids, is easily built of 1-by-12 shelving and 1-by.2 strips. To make a three- step bench, first cut 8-inch notches into one long edge of each of two 1 -by-12 boards 3 feet long.
2. To the inside of each stepped board, nail a 1 -by-2 leg. Then join the two stepped pieces with a 1-by-2 strip, 3 feet long, across the top so that the assembled framework will stand upright.
3. Nail 1 -by-2 strips across the tops of the sidepiece notches to frame the long edges of each shelf. Staple galvanized hardware cloth to the framing strips or, instead of hardware cloth, fit a third 1 -by-2 between the edge strips to make a slatted shelf.
4. Each shelf of the stepped bench will hold up to a dozen 4-inch pots or eight 6-inch pots, with all plants well ventilated through the wire mesh. The wood part s, especially the cut edges with exposed end grain, should be protected from rot with brushed-on copper naphthenate.
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That distinction resolved several mysteries. Why , for example, were poinsettias, so-called short-day plants, failing to flower in time for Christmas? Perhaps a watchman was routinely checking the greenhouse at night, sweeping a flashlight beam ahead of him. In the process he was halting the blooms. Or perhaps a small light used to illuminate a thermometer cast a faint glow. Perhaps a distant street lamp, or a light on a neighbor’s porch, could be seen from the greenhouse. In each case there were no blooms, and the explanation was the same: The poinsettias were being disturbed in the middle of the night. The plants, in effect given short nights, were simply waiting for longer uninterrupted darkness.
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=== Orchestrating a floral display ===
In a greenhouse many plants can produce flowers at a specific time, depending on when they are started, when the tips or buds are pinched, or when temperature or light are modified. The plants listed here respond particularly well to such treatment. The effect of these manipulations, however, cannot be predicted exactly, since no two greenhouses are exactly alike, and nature can throw off schedules with cloudy days or unseasonable temperatures.
The left-hand column of the chart gives normal blooming time with no special manipulation beyond the selection of a starting time; many of the plants listed bloom at any desired time if they are started sufficiently in advance. For closer control, the right- hand column describes special treatments to force blossoming out of season, delay it, or in a few cases, advance it. With most plants, the easiest way to advance blossoming is to start them earlier.
[NORMAL BLOOMING TIME IN A GREENHOUSE] --- [MANIPULATION TO RESCHEDULE BLOOM]
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[
ANTIRRHINUM MAJUS
SNAPDRAGON
Any season, 16 to 20 weeks after seeding
BEGONIA ELATIOR
RIEGER BEGONIA
Fall or winter, 14 to 16 weeks after cuttings are started
CALCEOLARIA HERBEOHYBRIDA
POCKET BOOK FLOWER
Spring, 29 to 32 weeks after seeding
CHRYSANTHEMUM MORIFOLWM
FLORISTS’ CHRYSANT}IEMUM
Fall, 14 to 16 weeks after cuttings are started
CROCUS HYBRIDS
CROCUS
Early spring, four to six weeks after potted bulbs are moved from the outdoor cold frame into the greenhouse
DIANTHUS CARYOPHYLLUS
CARNATION
Continuous, beginning 11 to 14 weeks alter cuttings are started
HYACINTH US ORIENTALIS
LARGE-FLOWERED HYACINTH
Early winter, two to four weeks after potted bulbs are moved from the outdoor cold frame into the greenhouse
IMPATIENS WALLERANA, I. NEW GUINEA HYBRIDS
PATIENT LUCY
Any season, 14 to 16 weeks after seeds are sown or cuttings are started
KALANCHOE HYBRIDS
KALANCHOE
Midwinter, 26 to 30 weeks after seeding
LILIUM LONGIFLORUM VARIETIES
EASTER LILY
Spring, 17 to 19 weeks after potted bulbs are moved from the outdoor cold frame into the greenhouse
MATHIOLA INCANA
COMMON STOCK
Winter and spring, 22 to 24 weeks after seeding
NARCISSUS HYBRIDS
TRUMPET DAFFODIL, HARDY TAZETTA NARCISSUS
Spring, two to three weeks after potted bulbs are moved from the outdoor cold frame into the greenhouse
PELARGONIUM HORTORUM
ZONAL GERANIUM
PELARGONIUM PELTATUM
IVY GERANIUM
Any season, 13 to 15 weeks after cuttings are started
RHODODENDRON (AZALEA) HYBRIDS
AZALEA
Spring, five to seven weeks after potted plants are moved into the greenhouse from outdoors
ROSA HYBRIDS
ROSE
Any season, six to eight weeks after the start of new growth
TAGETES ERECTA
AFRICAN MARIGOLD
Any season, 10 to 12 weeks after seeding
TULJPA HYBRIDS
TULIP
Spring, three to four weeks after potted bulbs are moved from the outdoor cold frame into the greenhouse
]
[
To delay bloom four weeks, pinch the tip when the plant is 8 inches tall.
For blooms out of season, illuminate to provide five weeks of 14 hour days, followed by nine to 11 weeks of 11-hour days. To delay bloom, extend the period of 14-hour days to as much as eight to 10 weeks.
For winter blooms, sow seeds in summer, and after 23 weeks keep night temperatures between 45° and 50°. Plants will bloom six to 10 weeks after cooler temperatures are provided.
For blooms out of season, illuminate cuttings to provide five weeks of 15-hour days, pinch the tips, then shade to provide seven weeks of 12-hour nights; they will bloom two to four weeks later. To delay bloom, extend the period of 15-hour days and pinch the tips of side branches when 4 inches long.
For blooms out of season, chill potted bulbs 10 to 14 weeks in the refrigerator at 40° to 48°, then move them to the greenhouse and keep the night temperature at 45° to 50° until blooms appear. To delay blooms, extend chilling period as long as 10 additional weeks at 35°.
To delay bloom, pinch tips. Plants pinched until early summer bloom 11 to 14 weeks after the• last pinch; those pinched until midsummer bloom in 20 to 22 weeks; those pinched until early fall bloom in six months. To reduce the time between the last pinch and blossoming by four to six weeks, illuminate for 20-hour days for four weeks starting when plants are 2 to 4 inches tall.
To advance bloom, shade for nine to 11 weeks of 14-hour nights.
To delay bloom, illuminate for 14-hour days until nine to 11 weeks before flowers are desired.
To delay bloom four weeks, pinch tips when the plant is 4 to 5 inches tall.
For blooms out of season, chill potted bulbs for 12 weeks in a refrigerator at 40 to 48°, then move them into the greenhouse and maintain a night temperature of 40° to 50°; they will blossom two to four weeks later. To delay bloom, extend the chilling period to as much as 24 weeks at 35°.
To delay bloom four weeks, pinch off flower buds as they appear.
To advance bloom, illuminate for six weeks of 14-hour nights; plants will blossom six to eight weeks later.
For blooms out of season, store potted bulbs for six weeks in a refrigerator at 40° to 48°, then move them into the greenhouse and keep the night temperature between 40° and 50°; they will blossom 17 to 19 weeks later. To delay bloom, extend the chilling period to as much as 26 weeks at 35°; for further delay after moving to the greenhouse, maintain a temperature of 50°. To advance bloom after moving to the greenhouse, increase the temperature to 72° to 78° for eight to 10 weeks before bloom is desired, and illuminate plants from midnight to dawn for three weeks when the plants are 4 inches tall.
To advance bloom, grow plants 16 to 20 weeks at night temperatures between 45° and 50°. To delay bloom, keep night temperatures above 60° for four weeks after seedlings are established.
For blooms out of season, Store potted bulbs for 15 weeks in a refrigerator at 40° to 48°, then move them into the greenhouse and keep the night temperature at 50° to 55°; they will blossom two to four weeks later. To delay bloom, extend the chilling period to as much as 23 weeks at 35°.
To delay bloom four weeks, pinch tips when the plant is 6 to 8 inches tall. To delay four more weeks, pinch side branches.
To advance bloom, chill plants six weeks outdoors (or in a refrigerator if possible) at 35° to 45°, then move them into the green- house and maintain a night temperature of 40° to 55°; they will blossom five to seven weeks later. To delay bloom, extend the chilling period to as much as 18 weeks.
To delay bloom, pinch tips of new growth six to eight weeks before flowers are desired.
To delay bloom four weeks, pinch the tip when the plant is 4 to 6 inches tall. To delay four more weeks, pinch the side branches.
For blooms out of season, chill potted bulbs 14 weeks in the refrigerator at 40° to 48°, then move them into the greenhouse and maintain a night temperature of 40° to 45°; they will blossom three to four weeks later. To delay bloom, extend the chilling period to as much as 27 weeks at 35°.
]
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Greenhouse gardeners now know that short-day, long-night plants such as poinsettias must be shielded from any night light if flowers are to be assured. By the same token these short-day plants—chrysanthemums , for example—can be deliberately lighted during the night to delay their blooms until they are wanted.
If you would like to use light and dark to schedule the blooming times of certain plants, select a place in the greenhouse where you can provide total darkness for short-day plants and extra light for long-day plants. You can use the darkest corner of your green house, since you will be creating an artificial environment.
In allotting this space, keep in mind that it will be off limits for other plants that might be affected in some unpredictable fashion by the abnormal day length you are creating. If you are lighting China asters at night to bring them into bloom in winter , for example, don’t let that light spill onto other plants.
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CONTROLLING THE SIZE AND SHAPE OF ROSES
To make a hybrid tea rose produce a blossom atop a long, straight stem, pinch off the top bud when it’s about 1/8 inch across. If the timing is just right this increases the stem’s length and delays the bloom about eight weeks.
If you want an extra-large single rose, use the technique called disbudding. When the top bud is about 1/4 inch across, rub off the buds growing at the bases of leaves on that cane, forcing the plant’s energy into the single flower.
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A TENT TO BLOCK LIGHT
To shield plants from light, you will need an opaque material. Professionals use a heavy grade of black cotton sateen. Don’t use what greenhouse suppliers call shade cloth; the latter is of varying density, blocking only part of the light, and is meant to protect plants from the burning rays of the sun. It admits far too much light to be effective in controlling a plant’s photoperiodic response.
You will need to support the opaque cloth in such a way that it can be lifted from the top and pulled back from the sides to admit sunlight and let air circulate during the day. And you will need to rig the cloth to suit the plants being sheltered. You can, for exam- pie, suspend the side curtains on wires supported by pipes or posts at the corners of a greenhouse bench. The curtains can be tied to these supports at night to exclude all light, and be pulled into the corners when not in use. A separate piece of cloth can be placed over the top of the frame so it laps down over the side curtains. This is simply removed each morning and put back each evening while the plants are getting short days and long nights.
Some plants, including poinsettias, have such an extreme sensitivity to light that they can sense the approach of light before dawn and retain their reaction to light as dusk deepens into dark. If you wish to delay the bloom of such a short-day plant by interrupting the dark period rather than extending the day length, the interruption must occur when it’s truly dark, that is, in the middle of the night, between 10p.m. and 2 a.m.
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MULTIPLYING BLOOM
Snapdragons are among the many greenhouse plants that can be made to produce abundant flowers through pinching. When the plant is about 4 inches tall, snip off the soft stem tip with your fingers, removing it above a pair of leaves near the top. This surgery stimulates lower buds to start growing.
When the branches that result are about 4 inches long, you can pinch off the tip of each one to produce still more branches. Repeated pinching makes the plant short and bushy, bearing many flower clusters instead of one.
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Arranging a greenhouse so you can provide special light or dark treatments for your plants takes careful planning. Until you gain experience, it’s better to start with one or the other. Either cover some short-day plants periodically to make them bloom, or supplement the sun in such a way that you delay bloom on short day plants or stimulate bloom on long-day plants.
To add sufficient light to lengthen the day, use ordinary 60 watt incandescent bulbs in reflectors available at photo supply stores. Place the units at 4-foot intervals along the plant bench, hanging each lamp about 2 feet above the top of the bench in such a way that it can be raised as the plants grow. Some greenhouse gardeners prefer to use brighter bulbs-from 75 to 100 watts- hung 4 feet above the tops of the plants. This arrangement eliminates the need for having to raise the lights but it adds heat to a crowded area-and temperature alters the influence of the light.
A difference of only 5 to 10 degrees in the night temperature can affect a poinsettia , for example. With a 60° temperature at night, the plant will flower as if it were getting 12 hours of uninterrupted darkness. If the temperature is 70° or higher, however, the plant will require a longer period of darkness to bring it into bloom.
To add to the complexity of manipulating light, the number of nights of shade or added light required to induce flowering will differ even among varieties of one species. Chrysanthemums , for example, may take from seven to 15 weeks of short days to flower, depending on the variety. Once started, the routine of lights on, lights off, cloth on, cloth off must be faithfully followed, and you must maintain careful records.
The final touch in controlling plant growth, and in many ways the most direct influence, is literally a final touch: pinching. Pinching is a kind of pruning. Instead of clipping through a stem, you remove either the growing tip of the stem or a bud, the fresh, soft bump that forms on a stem to produce a side branch or develop into a flower. You can use clippers if you like, but most gardeners pinch with their fingers, snipping off fresh growth by squeezing it be tween the nail of the thumb and the tip of the forefinger or rolling a bud off with the side of the thumb. Depending on what is snipped at what time, pinching can delay flowering, make flowers bigger or smaller, limit or multiply the number of flowers, and make the plant low and bushy or tall and slender.
A bud—occasionally more than one—appears at each joint where a leaf is attached to the main stem or branch. On some plants these buds can easily be seen, on others they cannot. But the buds are always there, awaiting a signal to grow into side branches, leaves or flowers. So long as the main stem keeps growing and forming new leaves at the top, the buds in the leaf joints below remain just buds waiting their turn to grow—they are restrained by a growth-inhibiting hormone released by the developing tissue at the stem tip. This hormone shuts off, permitting side branches to develop, when the stem tip stops growing and forms a flower. Pinching prematurely stops the hormone flow to control the way the stem, branches and flowers grow.
PINCHING TO SLOW FLOWERS
If you want to delay flowering, pinch off the top of the main stem before a flower bud starts there. By removing the developing tissue at the tip, you cut off the supply of growth inhibitor so that the side branches can sprout. The plant’s energy will go into the development of leaves and branches at the sides—mainly from buds immediately below the pinch—so that the plant fills out into a bushy shape and does not grow tall. The tip of the stem won’t flower, but many flower buds will appear on the new side branches. The result is a large number of moderate-sized blossoms, produced later than the single blossom that would have appeared at the stem tip if it had not been pinched.
The new side branches can in turn be pinched to induce further branching and even more flowers. A pompon chrysanthemum , for example, may bear up to a dozen flowers on a single stem. But if you pinch its main stem tip when it’s about 4 inches tall and its side branch tips three to four weeks later, that same plant might produce 100 flowers on 15 or 16 stems.
Eventually, it becomes too late to pinch. Once a plant starts to form flower buds—signaled to do so by its age, the length of the day, the temperature, its general health, crowded roots or some other indication that its time has come—the crucial growth hormone disappears; further pinching is not likely to induce attractive branching and instead only sacrifices flowers.
DISBUDDING FOR BIG BLOOMS
Tip pinching encourages the leaf-joint buds to grow. Doing it the other way round—letting the tips grow and pinching the leaf- joint buds, a technique called disbudding—has the opposite effect. If you let the tip of a stem (or side branch) grow, it will eventually start to produce a flower bud and stop producing growth inhibitor. If there are no leaf-joint buds to respond to the absence of inhibitor—because you have removed them—the plant’s energy will be shunted into enlarging the flower developing at the stem tip.
Disbudding is the technique to use for growing a large bloom on a tall stem for display in a vase. Leave the main stem tip unpinched, but remove all leaf-joint buds. The result will be one long, straight stem bearing one huge, perfect blossom.
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SUPPORTS FOR TALL FLOWERS
To keep long-stemmed flowers upright, nail four stakes, each 2½ feet tall, to the corners of the planting bench. Fasten wire around them, about 6 inches above the soil, and tie strings in both directions, spaced 6 inches apart.
When the plants are 9 inches tall, run a second level of string supports 6 inches above the first in the same pattern. These supports give each plant its own growing area and protect it from being crowded by wayward neighbors.
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By combining disbudding with tip pinching, you can make many kinds of plants arrange their branches and flowers to suit your taste at a time you choose. For a gardener new to the green house and eager to see it glowing, consider what pinching and disbudding can do for the African marigold. Sow the seed in September so that flowers can be expected in midwinter. Begin pinching the stem to encourage branching after two pairs of leaves are formed. As the plant grows, continue pinching to encourage more branching; remove any unwanted branches to improve future flower placement, and pinch off all but wanted flower buds to direct energy into producing larger flowers in the most effective places.
When you disbud, try to catch the flower buds early enough so they can be rolled off with the side of the thumb, leaving no trace behind. The earlier you disbud, the smoother the flower stem will be. Since the top flower bud is formed first, its appearance is your signal to watch for more buds lower down on the stem. In December and January you will be rewarded when your plant turns into what seems to be a hemispherical surface covered with blossoms. One greenhouse gardener claims that her pots of African marigolds can pass for majolica, the richly enameled Italian pottery, because the plants are so uniformly compact and the blooms so brilliant. If you practice your prowess at pinching and disbud ding on a follow-up planting of marigolds in January, you can have equally spectacular blooms in April and May.
SCHEDULING CARNATIONS
The interdependence of flower timing and flower size is illustrated by the effects of these techniques on the greenhouse carnation. Cuttings rooted in January, if left unpinched, will produce conventional flowers in April and May. If you remove all flower buds on each stem except the main one, each stem will bloom on its normal schedule but will produce a single, large, perfect bloom. In contrast, if you pinch the center stem before it begins forming a flower, you delay flowering for several weeks and at the same time stimulate the branching of perhaps half-a-dozen new stems. In order to achieve maximum flower production, commercial carnation growers continue to pinch off potential flower stalks until midsummer; by that time the original single stem will have multi plied to a dozen or more. Due to the increased size of the plant and its abundant foliage, it will produce a great number of large flowers during the following fall, winter and spring. So you have the option of growing one great exhibition bloom early or abundant flowers for cutting later on, depending on the way you pinch.
Pinching and disbudding achieve their maximum effect in the “standard”—a tall, slender plant with a single straight stem topped by a large cloud of foliage and flowers, or even just a huge solitary blossom. To create a standard, remove all leaf-joint buds, allowing only the main stem tip and the leaves growing from the main stem to remain. When the stem reaches the desired height, pinch it off.
One gardener, who each year produces a pair of bright, salmon-colored geranium standards (often called tree geraniums) on schedule for Easter, insists that “one standard is useless; you must have pairs.” If you position one standard on either side of an object of interest, from a doorway to a fireplace to a bench, that focal point acquires an élan that it could take on in no other way.
You can start a pair of geranium standards any time of the year in a greenhouse. If your target is a special occasion, begin 12 to 15 months in advance. Select small, healthy plants with sturdy, straight stems, and start at least four standards so you have some leeway in selecting the two that look most like identical twins.
Leave the tip of the main stem intact until it reaches the desired height, perhaps 3 or 4 feet, tying it loosely with soft cord to a stake of bamboo or reed an inch or so away from the stem.
When the plant has reached the desired height, pinch the tip. The new shoots that result are in turn pinched to encourage further branching until the long main stem has acquired a shapely crown. Then wait for the flowers to develop. The leaves that grow along the stem will fall off naturally with age, or they can be removed as top foliage develops. In time, the long stem may become stiff enough so the stake can be removed.
Fuchsia, heliotrope and lantana can also be pinched to pro duce standards. It takes them about two years to develop good top growth. Standards will live many years if they are fertilized monthly and moved to larger pots before their roots become crowded.
THE LONG-STEMMED ROSE
Precision pinching becomes an art with the hybrid tea rose; producing a single beautiful bloom atop a long stem is a traditional challenge for greenhouse gardeners. One enthusiast, who each January presents his daughter with blooms of the Tropicana rose to mark her wedding anniversary, is coping with the challenge of making the right pinch at the right time to attain the longest possible stem. It is, as he puts it, precisely a matter of “a pinch in time.” The pinch must be made at the time a flower bud about 1/8 inch long has formed on an upright branch. At this stage the branch is immature enough so the new growth thus stimulated will merge into it and add to the final stem length. If the pinch is made too early, when the flower bud is smaller, or too late, when the flower bud is larger, the resulting growth won’t blend into the stem but will take off in a new direction, and the long-stemmed bud being sought will be lost.
This rose gardener, after years of experimentation, has created long-stemmed beauties that would delight many greenhouse owners—but none satisfy him. The challenge of the ideal blossom at the ideal time still has to be met. It’s just this challenge that makes the greenhouse a special world of gardening adventure.
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** The amateur’s exotic favorite — orchids **
The most glamorous of all greenhouse plants, and the one that is most particular in its demands, is undoubtedly the orchid. Although some species grow on window sills like ordinary house plants, most are very special plants with unusual habits and requirements. Some require cold and can be found only in such unlikely places as Alaska and the Himalayas; some need the steamy heat of the Brazilian jungle. There are orchids that live quite literally in the air, suspended from trees, with free-ranging roots that take their nourishment from the surrounding atmosphere. Others live more conventionally on the ground, but even these barely make contact with the soil; their roots move just beneath the fallen leaves and feed on decayed vegetable matter.
Subtle combinations of humidity, light, temperature and moving air may be required to support growth. In the tropics, the natural homeland of the popular greenhouse orchids, some species thrive on the sultry air of the lowlands, while others need the cooler mountainsides. Most, in addition, are accustomed to being washed regularly by tropical rains and stirred by warm breezes. Little wonder that for years orchid culture was the hobby of people who could afford conservatories and full-time gardeners to tend them.
But the modern greenhouse with its semiautomatic environ mental controls has brought orchid growing within the reach of amateurs like Henry Rothman and Ann and H. Phillips Jesup, whose greenhouses are pictured here. Rothman specializes in orchids with spectacular flowers, the Jesups in miniature orchids. Their greenhouses, marvels of automation, include such devices as separate thermostats to regulate day and night temperatures, humidistats that activate misting jets when the moisture falls below a certain level, and fans that keep the air in continuous motion 24 hours a day. In Henry Rothman’s lean-to, attached to one wall of his home, fluorescent lights on the dark side of the greenhouse are triggered by an electric eye that monitors the natural light—in effect duplicating the rising and setting of the sun.
Blooming orchids in Henry Rothman’s greenhouse are massed on a platform against a fiberglass sculpture, visible from the dining room through sliding glass doors.
- Awash in splendid hybrids -
Henry Rothman began growing orchids in 1967 with two familiar types—Phalaenopsis and Paphiopedilum—in a glass-enclosed in door planter. Six years later he was filling up a greenhouse that measured 16 by 31 feet; two years after that, 1,300 plants were providing a succession of the world’s most beautiful, delicate flowers. The greenhouse largely takes care of itself—Rothman needs to water only once a week.
Surrounded by orchids of at least a dozen different kinds, Rothman and his wife examine a hybrid variety named after her, Paphiopedilum Fran Rothman. Because many of Rothman’s orchids are air plants, they take up relatively little room—and most of that is air space. The pots and teak baskets they grow in simply supply support; the roots themselves live outside, gathering airborne nutrients.
Rothman’s award-winning orchid hybrid, Laeliocattleya Dorset Gold
Orchidhurst (right), has double blooms each measuring 6 inches across.
A hybrid of the Vanda and Ascocentrum orchids, this 16-inch specimen of Ascocenda Lady Boonkua blooms twice a year in the Rothman greenhouse. (right) Brassavola nodosa clings to tree -fern bark, as it does in its native Honduras. The flowers, 2½ to 3 inches wide, are fragrant at night, inspiring the name lady-of-the-night.
Delicate flowers spring from a spray of the hybrid aerial orchid Dendrobium phalaenopsis Dale Takiguchi.
- A Lilliputian collection -
Ann and H. Phillips Jesup, who have been growing orchids ever since 1953, have one of the most unusual orchid collections in the country: they have 5,000 miniature plants, with flowers so small that they are measured in millimeters. The entire collection fits into a greenhouse 18 feet wide and 30 feet long, and the standard clay pots for their plants are only 1 inch across. Ann Jesup, an amateur potter, often buys clay and makes her own.
Ann Jesup removes a spent bloom as her husband waters. Although the Jesups group their orchids according to the plants’ cultural requirements, there are so many shadings of difference in the requirements of the tiny plants that each orchid must be watered individually, on a daily basis.
Oncidium pusillum blooms in a snail shell less than 2 inches across.
The flower measures 20 millimeters across (about 3/4 inch).
A single plant of the O’Brieniana variety of Masdevallia simula is shown actual size at left; the pot is 1 inch in diameter. Although the flower is only 3/4 inch across, it resembles a standard orchid.
Growing in a pot made by Ann Jesup is a Lepanthes woodiana, shown in actual size. The flower is only 1/8 inch wide.
The shimmering flowers of Lepanthes, pictured at left in one of the Jesups’ miniature pots, are each only ¼ inch long.
Standing on 8-inch bricks, these 21 miniature orchids from the collection of Ann and Phillips Jesup range from 1 to 10 inches high. in addition to being small, some are so rare that they cannot be bought commercially. The Jesups brought back many of them from visits to the West indies, and some were brought back from South America by traveling friends.
The orchids in the photograph at left are keyed to the drawing below.
1. Sophronitis cernua
2. Brassotonia John M. Miller
3. Masdevallia wageneriana
4. Polysfachya fallax
5. Masdevallia simula Q’Brieniana
6. Leparithes woodiana
7. Derdrobium coerulescens
8. Pleurothallis phalangifera
9. Barbosella species
10. Pleurothallis fanceola
11. Ascocenda Little Leo
12. Masdevallia species
13. Polystachya aconitiflora
14. Dipterarithus species
15. Lepanthes species
16. Oncidium pusillum
17. Pleurothallis sibatensis
18. Sophronitis coccinea
19. Leptotes unicolor
20. Restrepia species
21. Sophronitis rosea
Articles in this Guide are based on now-classic Time-Life Encyclopedia of Gardening Series from the 1970s ... a timeless series, some titles of which are still available in libraries and bookstores... see our Amazon Store for purchasing options.