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CATTLEYA

KAT-lee-uh

Cattleyas are among the most popular Orchids. Their culture is often used as the basis for comparison with other types of Orchids. Cattleyas and their related hybrids come in many colors, shapes, forms and sizes. Culture varies only slightly among most of these. This sheet is a general guide to basic cattleya culture. Like many other cultivated Orchids, cattleyas are epiphytes, or air plants. They have developed water-storage organs, called pseudobulbs, and have large, fleshy roots covered with spongy, water-retentive velamen. They are accustomed to being dry at roots between waterings, and therefore should be potted in free draining media.

Light is the most important factor in growing and flowering cattleyas, whether in a greenhouse or in the home. Bright light to some sun should be given to the plant, with no direct sun in the middle of the day. This means an east, shaded south (as with a sheer curtain) or west window in the home, and 50 to 70 percent full sun in a greenhouse (3,000 to 5,000 foot-candles). Leaves should be a medium green color, pseudobulbs erect and requiring no staking.

Temperatures should be 55 to 60 F at night and 70 to 85 F during the day. Seedlings should have night temperature five to 10 degrees higher. A 15- to 20- degree differential between day and night is recommended, especially for mature plants. Higher day temperatures can be tolerated (up to 95 F), if humidity, air circulation and shading are increased.

Water should be provided in two ways: in the pot by watering and in the air as humidity. Watering in the container is dictates by many criteria: size and type of the vessel, temperature, light, etc. Mature cattleyas need to dry out thoroughly before being watered again,. Seedlings need more constant moisture. Compare the weight of a dry pot of the same size and type of mix; it can indicate if a plant needs water by the relative weight -- light means dry, heavy means wet. If in doubt, it's best to wait a day or two until watering. Plants in active growth need more water than plants that are resting. Water below 50 F may injure plants, as will water softened by the addition of salts.

Fertilize on a regular schedule. In fir bark, a high-nitrogen (such as 30-10-10) formulation, or a simple proportion, is used. Otherwise, use a balanced fertilizer. When in active growth, plants need fertilizer at least every two weeks, and when not actively growing, once a month. Fertilizer can also be applied with every watering at one-quarter the recommended dilution. Thorough flushing with clear water every month is recommended to prevent the build up of fertilizer salts.

Potting is necessary when the rhizome of the plants protrudes over the edge of the pot or the potting medium starts to break down and drain poorly (usually after two to three years). It is best to repot just before new roots sprout from the rhizome, after flowering or in the spring.

Mature cattleyas are usually potted in coarser potting material than are seedlings. Until the plant has at least six mature pseudobulbs, it generally should be put into a larger pot and not divided. If dividing a plant, three to five pseudobulbs per division are required. Select a pot that will allow for approximately two years of growth before crowding the pot. Pile mix against one side of the pot and cut any dead roots. Spread the firm, live roots over the pile, with the cut rhizome against the side of the pot. Fill the pot with medium, working it around the roots. Pack firmly and stake if necessary. Keep the plant humid, shaded and dry at the roots until new root growth is seen.

Catasetum

kat-a-SEE-tum

This unusual group of Orchids offers fascinating, waxy flowers that often have the peculiar habit of discharging their pollen masses (pollonia) onto pollinators. Almost always deciduous, the pseudobulbous plants have strict growing and resting periods. Most flower before entering a dormant period when they drop their leaves.

LIGHT should be strong, especially near the end of the growth period. Early in the annual growth cycle, plants will tolerate less light, from 1,500 to 3,000 foot-candles. Plants grow best with light levels of 3,000 to 6,000 foot-candles, or one-half to three-fourths full sun. As pseudobulbs mature, harden them by giving slightly more light.

TEMPERATURE reflect the fact these Orchids are native to hot tropical areas and grow during the rainy summer months. During this growing period, day temperatures of  80 to 100 F and night temperatures of 60 to 65 F are beneficial. After growths mature, temperatures can be reduced to 55 F at night, with day temperatures of 70 to 85 F.

WATER is a critical factor for the production of large pseudobulbs that result in best flowering. A great quantity of water must be stored by the plant in a relatively short growing season. Water heavily as new leaves are forming. As the pseudobulb matures, gradually reduce watering frequency. Leaves will yellow and drop. At this time, watering should be stopped completely until new growth begins. Water during this dormant period only if the pseudobulbs shrivel severely.

HUMIDITY should be 40 to 60 percent. This can be provided in the home by placing the plants on trays of gravel, only partially filled with water so that the plants do not sit in the water. Air should always be moving around the plants to prevent fungal or bacterial disease, especially if high humidity or cool temperatures exist. In the greenhouse, the humidity is best increased by use of a humidifier. Evaporative cooling increases humidity while cooling the air.

FERTILIZE and the water regularly to produce strong pseudobulbs. Use a high-nitrogen formulation (such as 30-10-10) while the plants are in active growth, slowly tapering off as pseudobulbs form. A blossom-booster formulation (such as 10-30-20) should be used in the autumn, except for plants that normally bloom in the spring. Frequent applications of dilute concentrations of fertilizer are more effective than occasional applications of strong concentrations.

POTTING should be timed to coincide with the initiation of new growth, usually in the spring. New roots will be produced quickly at that time, and plants will experience minimal setback. These plants have vigorous root systems and require a rich, moist potting medium during the growing season. Many growers bare-root their plants during resting period to ensure dryness at that time. Fine-grade media are common for smaller pots; medium-grade media are used only in larger pots. Sphagnum moss is used successfully for plants in many areas, as it provides tremendous water- and fertilizer-holding capacities. Some plants can be grown on slabs of tree fern or other material, which makes it easier to keep them dry during dormancy; however, it is harder to keep them moist while growing. When well grown, these Orchids can be divided down to one mature pseudobulb and will then flower on the next mature growth. Spider mites are common pest of these Orchids when in leaf. Control spider mites by keeping humidity high or spraying with recommended miticides.

Phalaenopsis

fail-eh-NOP-sis

Phalaenopsis, the moth Orchid, is perhaps the best Orchid for growing in the home, and is also a favorite with greenhouse growers. Well-grown plants can flower often, sometimes with a few flowers throughout the year, though the main season is late winter into spring. Average home temperatures and conditions are usually sufficient. Flower stems on certain hybrids can be forced to rebloom by cutting the tip off after the initial flowering. Only healthy plants should be induced to flower repeatedly. Culture for Doritis, a related genus, thought by some to be conspecific with Phalaenopsis, and Doritaenopsis, a hybrid between the two genera, is the same as for pure Phalaenopsis.

Light is easy to provide for Phalaenopsis. They grow easily in a bright window, with little or no sun. An east window is ideal in the home; shaded south or west windows are acceptable. In overcast, northern winter climates, a full southern exposure may be needed. Artificial lighting can easily be provided. Four fluorescent tubes in one fixture supplemented by incandescent bulbs are placed 6 to 12 inches above the leaves, 12 to 16 hours a day, following natural day length. In a greenhouse, shade must be given; 70 to 85 percent shade, or between 1,000 to 1,500 foot-candles, is recommended. No shadow should be seen if you hold your hand one foot above a plant's leaves.

Temperature for Phalaenopsis should usually be above 60 F at night, and range between 75 and 85 F or more during the day. Although higher temperatures force faster vegetative growth, higher humidity and air movement must accompany higher temperatures, the recommended maximum being 90 to 95 F. Night temperatures to 55 F are desirable for several weeks in the autumn to initiate flower spikes. Fluctuating temperatures can cause bud drop on plants with buds ready to open.

Water is especially critical for Phalaenopsis. Because they have no major water-storage organs other than their leaves, they must never completely dry out. Plants should be thoroughly watered and not watered again until nearly dry. In the heat of summer in a dry climate, this may be every other day; in the winter in a cool northern greenhouse, it may be every 10 days. Water only in the morning, so that leaves dry by nightfall, to prevent rot.

Humidity is important to Phalaenopsis, the recommended humidity being between 50 to 80 percent. In humid climates, as in greenhouses, it is imperative that the humid air is moving. Leaves should  be dry as soon as possible, always by nightfall. In the home, set the plants on trays of gravel, partially filled with water, so that the pots never sit in water.

Fertilize on a regular schedule, especially if the weather is warm, when the plants are most often growing. Twice-a-month applications of high-nitrogen fertilizer (such as 30-10-10) are appropriate where bark-based media are used. Otherwise, a balanced fertilizer (such as 10-30-20) can be applied to promote blooming. Some growers apply fertilizer at one-quarter strength with every watering; this is best for warm, humid conditions. When cooler, or under overcast conditions, fertilizer should be applied twice per month at weak strength.

Potting is best done in the spring, immediately after flowering. Phalaenopsis plants must be potted in porous mix. Potting is usually done every one to three years. Mature plants can grow in the same container until the potting medium starts to decompose, usually in two years. Root rot occurs if the plants are left in a soggy medium. Seedlings usually grow fast enough to need repotting yearly, and be repotted in fine-grade medium. Mature plants are potted in a medium-grade mix. To repot, remove all the old medium from the roots, trim soft, rotted roots, and spread the remaining roots over a handful of medium in the bottom of a new pot. Fill the rest of the pot with medium, working it among the roots, so that junction of roots and stem is at the top of the medium.


Dendrobium  

den-DROH-bee-um

Dendrobium is a diverse genus of Orchids with different cultural needs. Many go through a growth phase during the course of one year, and must be given water and temperature to mach these periods of growth and rest. Flowers can last one day to many weeks, depending on the type. Owing to the extreme diversity of the genus, we have categorized culture according to the following main types:

PHALAENANTHE

Evergreen for several years, with thin, tall pseudobulbs, terminal inflorescence, usually appearing in the autumn or twice a year (see culture).

Species such as Den. affine, Den. bigibbum (phalaenopsis), Den. dicuphum and Den. williamsianum.

Culture Grow warm year round (see below); 60 F nights; water and fertilize heavily when roots appear from new growth; medium light; reduce water and fertilizer after growth finishes. If a short  (three- to four-week), cooler (55 F) dry rest is given, and then plants are warmed again (60 F minimum), another growth may mature during winter and flower in the spring. Treat this growth as a summer growth cycle. These grow well with phalaenopis, except for the rest period. Plants will go deciduous if grown too cool and dry.

SPATULATA (Antelope Type)

Evergreen for several years. Most are large, vigorous plants with long-lasting flowers in summer to several times a year. Species such as Den. antennatum, Den. canalixulatum, Den. discolor, Den. gouldii, Den. johannis, Den. lineale (veratrifloum), Den. statiotes, Den. stebloceras and Den. taurinum.

Culture Warm all year (60 to 65 F nights, 75 to 90 F days); no rest period; can be kept cooler in winter if dry; medium to high light.

DENDROBIUM  Most of plants are pendulous, with leaves all along the canes that most often drop with onset of cooler, drier weather. One to five flowers per node are borne from the nodes of the leafless canes in midwinter through early spring.

Group 1

Species such as Den. chrysanthum, Den. friedricksianum, Den. nobile and Den. wardianum.

Culture Growth period in summer; give warmth, water and fertilize heavily from when roots appear until top leaf appears on canes. Then give high light, little or no water, no fertilizer, cool nights (40 to 50 F). In other words, forget about them.

Group 2

Species such as Den. anosmum (superbum), Den. crassinode, Den. falconeri, Den. heterocatpum (aureum), Den. loddigesii, Den. moniliforme, Den. parishii, Den. primulinus and Den. transparens.

Culture Same as Group 1, but winter nights 55 F. Deciduous species need virtually no water in winter.

CALLISTA

Most are pseudobulbous plants with pendent inflorescence.

Species such as Den. aggregatum (now properly lindleyi), Den chrysotoxum, Den. densiflorum, Den. farmeri and Den. thyrsiflorum.

Culture Summer give warmth (60 to 90 F), medium light, medium quantities of water and fertilizer. Winter keep cool (50 F nights), medium light, just enough water to keep pseudobulbs from shriveling, no fertilizer.

LATOURIA          

Leaves at top of pseudobulbs are large and leathery, inflorescence erect, flowers commonly yellow-green.

Species such as Den. atroviolaceum, Den. macrophyllum, and Den. spectabile.

Culture Same as antelope types, but cooler and drier when resting in winter.

FORMOSAE ( Nigrohirsutae Type)

Canelike pseudobulbs, with black hairs on leaf sheaths and pseudobulbs often apparent, leading to popular name nigrohirsutae. Flower usually white, up to 4 inches across, two to three together from near the end of the pseudobulb. Long lasting. Species such as Den. bellatulum, Den. dearii, Den. draconis, Den. formosum, Den. infundibulum, Den. lowii, Den. lyonii, Den. margaritaceum, Den. sanderae and Den. schuetzii.

Culture Intermediate to cool year round, 50 to 60 F nights, maximum 85 F days. Water and fertilize when growing; give a slight short rest (dry) when growth is completed. Keep barely moist until growth starts again.

OTHER SPECIES

Among the popular types are Den. linguiforme, Den. tetragonum, Den. gracillimum and Den. cuthbertsonii (sophronitis).

Culture Depends on the plant's native environment. It is generally safe to grow them intermediate to warm (55 to 60 F at night), drying them out in winter (or as growth stops). Hybrids between sections vary in culture.
Dendrobium  

den-DROH-bee-um

Dendrobium is a diverse genus of Orchids with different cultural needs. Many go through a growth phase during the course of one year, and must be given water and temperature to mach these periods of growth and rest. Flowers can last one day to many weeks, depending on the type. Owing to the extreme diversity of the genus, we have categorized culture according to the following main types:

PHALAENANTHE

Evergreen for several years, with thin, tall pseudobulbs, terminal inflorescence, usually appearing in the autumn or twice a year (see culture).

Species such as Den. affine, Den. bigibbum (phalaenopsis), Den. dicuphum and Den. williamsianum.

Culture Grow warm year round (see below); 60 F nights; water and fertilize heavily when roots appear from new growth; medium light; reduce water and fertilizer after growth finishes. If a short  (three- to four-week), cooler (55 F) dry rest is given, and then plants are warmed again (60 F minimum), another growth may mature during winter and flower in the spring. Treat this growth as a summer growth cycle. These grow well with phalaenopis, except for the rest period. Plants will go deciduous if grown too cool and dry.

SPATULATA (Antelope Type)

Evergreen for several years. Most are large, vigorous plants with long-lasting flowers in summer to several times a year. Species such as Den. antennatum, Den. canalixulatum, Den. discolor, Den. gouldii, Den. johannis, Den. lineale (veratrifloum), Den. statiotes, Den. stebloceras and Den. taurinum.

Culture Warm all year (60 to 65 F nights, 75 to 90 F days); no rest period; can be kept cooler in winter if dry; medium to high light.

DENDROBIUM  Most of plants are pendulous, with leaves all along the canes that most often drop with onset of cooler, drier weather. One to five flowers per node are borne from the nodes of the leafless canes in midwinter through early spring.

Group 1

Species such as Den. chrysanthum, Den. friedricksianum, Den. nobile and Den. wardianum.

Culture Growth period in summer; give warmth, water and fertilize heavily from when roots appear until top leaf appears on canes. Then give high light, little or no water, no fertilizer, cool nights (40 to 50 F). In other words, forget about them.

Group 2

Species such as Den. anosmum (superbum), Den. crassinode, Den. falconeri, Den. heterocatpum (aureum), Den. loddigesii, Den. moniliforme, Den. parishii, Den. primulinus and Den. transparens.

Culture Same as Group 1, but winter nights 55 F. Deciduous species need virtually no water in winter.

CALLISTA

Most are pseudobulbous plants with pendent inflorescence.

Species such as Den. aggregatum (now properly lindleyi), Den chrysotoxum, Den. densiflorum, Den. farmeri and Den. thyrsiflorum.

Culture Summer give warmth (60 to 90 F), medium light, medium quantities of water and fertilizer. Winter keep cool (50 F nights), medium light, just enough water to keep pseudobulbs from shriveling, no fertilizer.

LATOURIA          

Leaves at top of pseudobulbs are large and leathery, inflorescence erect, flowers commonly yellow-green.

Species such as Den. atroviolaceum, Den. macrophyllum, and Den. spectabile.

Culture Same as antelope types, but cooler and drier when resting in winter.

FORMOSAE ( Nigrohirsutae Type)

Canelike pseudobulbs, with black hairs on leaf sheaths and pseudobulbs often apparent, leading to popular name nigrohirsutae. Flower usually white, up to 4 inches across, two to three together from near the end of the pseudobulb. Long lasting. Species such as Den. bellatulum, Den. dearii, Den. draconis, Den. formosum, Den. infundibulum, Den. lowii, Den. lyonii, Den. margaritaceum, Den. sanderae and Den. schuetzii.

Culture Intermediate to cool year round, 50 to 60 F nights, maximum 85 F days. Water and fertilize when growing; give a slight short rest (dry) when growth is completed. Keep barely moist until growth starts again.

OTHER SPECIES

Among the popular types are Den. linguiforme, Den. tetragonum, Den. gracillimum and Den. cuthbertsonii (sophronitis).

Culture Depends on the plant's native environment. It is generally safe to grow them intermediate to warm (55 to 60 F at night), drying them out in winter (or as growth stops). Hybrids between sections vary in culture.


PESCATOReA

pes-ca-TOR-e-a

This genus originates from tropical rainforest in areas of Central and South America .  Many of the selections available are newly collected and/or hybridized.  The natural environments of origin are at moderately high elevations therefore the plants thrive in intermediate, high humidity conditions with particularly good air circulation.

Light  The main rule to remember is the higher the light the higher the humidity and air circulation.  Greenhouse conditions should be 1200 to 1500 foot candles maximum.  Be careful to avoid direct sunlight on the leaves which can produce plant damaging sunburn.

Temperature  This genus grows best when conditions are kept uniform year around.  The lowest should be 50 F the highest can be around 75 F just be sure to adjust watering accordingly.  Temperatures that get too high when the plant is insufficiently water will result in leaf and bloom stress.

Water  This genus is very intolerant of dehydration.  The plant has no pseudobulbs or thick-substanced leaves in which to store water so frequent watering may be necessary especially if temperatures are high and/or humidity is low.  Keep the plant moist year-round however avoid letting water stand on the leaves or flowers.  The plant likes to be damp but not soggy.

Humidity  High humidity 80-90% is optimum.  Floating mist with good air circulation encourages new growth in this genus.  Again however, avoid standing water.

Fertilizer Use a balanced house plant fertilizer such as 20-20-20 at half strength once a month.  You can go a little stronger or more often if plants are putting out new growths.

Potting  The more access to air in the soil mix the better.  These plants are grown best in light mixtures, such as sphagnum or even straight perlite.  Hanging baskets or slotted rafts provide the air circulation needed and also display the flowers nicely.  

Oncidium

on-SID-ee-um

This is an extraordinarily large and diverse New World genus with an equally diverse number of habitats. Oncidiums may originate anywhere from sea level in the tropics to high elevations of the Andes. This obviously makes cultural generalizations difficult. More specific instructions may be available from the grower. Some genera included are Aspasia, Brassia, warm-growing miltonias (often called the Brazilian type) and many of their hybrids.

Light needs can vary from bright to nearly full direct sun depending on the species. Most will thrive with one to several hours of sun a day. Generally, thicker-leaved plants, such as "mule-ear" and "equitant" oncidiums, can stand more light. In a greenhouse, 20 to 60 percent shade is required, or about 2,000 to 6,000 foot-candles, depending on the plants. In the home, east, south or west windows are ideal. Many artificial light: Four fluorescent tubes supplemented with incandescent bulbs and places 6 to 12 inches over plants are necessary for proper growth. Metal-halide and sodium-vapor bulbs also provide sufficient light without needing to be so close to the plants.

Temperatures for this group are generally considered intermediate to warm: 55 to 60 F at night , and 80 to 85 F during the day. Temperatures up to 95 to 100 F are tolerated if humidity and air movement are increased as the temperatures rise, a good general rule in any case.

Water requirements vary with the type of plant. Generally, plants with large fleshy roots or leaves need less-frequent watering than thin-leaved or thin-rooted plants. Watering should be thorough, and the medium should dry at least halfway through the pot before watering again. This may be every two to 10 days depending on weather, pot size and material, type of Orchid and type of potting medium. Plants not actively growing should be watered less; many species have winter rest periods.

Humidity should be between 30 and 60 percent. May oncidiums require less humidity than other Orchids. Most greenhouses have adequate humidity. In the home, placing the plants above moist pebbles in trays is ideal.

Fertilize regularly while plants are actively growing. Applications of 30-10-10 formulations twice a month are ideal for plants in a bark-based potting medium. A 20-20-20 formulation should be used on plants in other media or slabs. If skies are cloudy, applications once a month are sufficient.

Potting should be done when new growth is about one-half mature, which is usually in the spring. Fine-grade potting media are usually used with fine-rooted plants and coarser mixes with large-rooted plants; the standard size is medium grade. The plant should be positioned in the pot so that the newest growth is farthest away from the edge of the pot, allowing the maximum number of new growths before crowding the pot. Spread the roots over a cone of potting medium and fill in around the roots. Firm the medium around the roots. Keep humidity high and potting medium dry until new roots form.

Equitant and mule-ear oncidiums, as well as other fleshy-leaved or large-rooted plants, can be grown on slabs of cork bark or tree fern or in pots filled with a coarse, well-drained medium such as charcoal. This allows the drying between waterings that these types need.

Phaius



Phaius tankervilliae, also called Phaius grandifolius (nun's Orchid)

These Orchids produce brilliantly colored flowers in combinations of yellow, white and red, often as large as 4 inches across, growing on a single stalk. Blossoms are characterized by tubular lips. Most species are earth dwellers, found in swampy soil, but some are tree-growing. The plants are notable for their leaves as well as flowers, since they may become 3 feet tall and add a tropical touch to a greenhouse or to a garden in a warm climate. Nun's Orchid has short egg-shaped pseudobulbs; heavy, folded 3-foot leaves; and a 4-foot flower spike that bears 10 to 20 fragrant flowers in the spring and summer. The sepals and petals are white on the outside and reddish inside, with yellow edges. Ruffled and tubular, with a short spur, the lip is white; it has a yellow throat and sides colored dark burgundy and purple.

HOW TO GROW. Intermediate to warm temperatures suit the nun's Orchid. In the winter it grows well if it is given temperatures of 65 to 75 degrees in the daytime and 55 to 60 degrees at night; in summer, if kept moist and shaded, it adjusts to higher temperatures. Provide filtered sunlight or 1,000 to 1,500 foot-candles of artificial light for 14 to 16 hours daily, with humidity of 40 to 60 percent or higher. Pot plants in a mixture of 2 parts coarse peat moss, 2 part sandy loam and 1 part each perlite and fine bark; this terrestrial plant requires liberal watering with good drainage. Fertilize the plants at every third watering with a balanced Orchid fertilizer, such as 18-18-18, dilute to half the strength recommended on the label. Repot phaius Orchids every two or three years. To propagate additional plants, divide plants at the end of a growing season so that you can place at least three pseudobulbs in each pot. To make new plants from cuttings or "slips", after flowering has stopped, cut the flower stalks into 6-inch pieces, each with at least two joint like nodes. Place these cuttings on moist sand to root.

Paphiopedilum

paff-ee-oh-PED-ih-lum

The Lady's-Slipper Orchid

Paphiopedilums, the lady's-slipper Orchids, originate in the jungles of the Far East including Indonesia. They are semiterrestrial, growing in humus and other material on the forest floor, on cliffs in pockets of humus and occasionally in trees. They are easy to grow in the home, under lights or in the greenhouse.

Light is easier to provide for paphiopedilums than many other types of Orchids. They require shady conditions, as in the home in an east or west window, or near a shaded south window. In the greenhouse, shade must be provided. Give about 1,000 to 1,500 foot-candles. In the home, fluorescent lighting is excellent; suspend two or four tubes 6 to 12 inches above the leaves.

Temperatures for paphiopedilums cover a considerable range. Paphiopedilums are traditionally separated into two groups: the warm-growing mottled-leaved types and the cool-growing green-leaved types. A third, increasingly popular group is the warmer-growing strap-leaved multifloral paphiopedilums. Warm-growing types should be kept at 60 to 65 F during the night, and 75 to 85F or more during the day. Cool-growing types should be kept at 50 to 60 F during the night and 75 to 80 F during the day. However, many growers raise all plants in the same temperature range with excellent results. The plants can stand night temperatures in the 40s if necessary (as when grown outside in mild climate), as well as temperatures to 95 F. Care must be taken to protect the plants from rot when cold (keep humidity low, and avoid moisture on leaves or in the crown of the plants), and also to protect from burning when hot (shade more heavily and increase humidity and air movement around the plants).

Water must be available at the roots constantly, because all plants in this genus have no pseudobulbs. All of these plants need a moist medium -- never soggy, but never dry. Water once or twice a week.

Humidity for paphiopedilums should be moderate, between 40 to 50 percent, which can be maintained in the home by setting the plants on trays of gravel, partially filled with water, so that the plants never sit in water. In a greenhouse, average humidity is sufficient. Using an evaporative cooling system in warm climates can increase the humidity. Air movement is essential, especially when humidity is high.

Fertilize on a regular schedule, but care must be taken to avoid burning of the fleshy, hairy roots. High-nitrogen fertilizers (such as 30-10-10) are recommended when potted in any fir-bark mix. In warm weather, some growers use half-strength applications every two weeks; others use one-quarter strength at every watering. It's important to flush with clear water monthly to leach excess fertilizer, which can burn roots. In cool weather, fertilizer applications once a month are sufficient.

Potting should be done about every two years, or as the medium decomposes. Seedlings and smaller plants are often repotted annually. Mixes vary tremendously; most are fine- or medium-grade fir bark, with varying additives, such as perlite (sponge rock), coarse sand and sphagnum moss. Moisture retention with excellent drainage is needed. Large plants can be divided by pulling or cutting the fans of the leaves apart, into clumps of three to five growths. Smaller divisions will grow, but may not flower. Spread the roots over a small amount of medium, so that the junction of roots and stem is buried 1/2 inch deep in the center of the pot. Do not overpot; an average plant should have a 4- to 6-inch pot.

Vanda

VAN-da

The Vanda Alliance is made up mostly of warm- and full-sun-growing Orchids with colorful flowers. Originating in tropical Asia, they are easily grown in warm climates, where plants are cultivated outside in light shade, such as in a bath house. In climates where winters are cold, they are often summered outside, and grown inside during the winter in a sunny window, or year round in a greenhouse. Smaller growing ascocendas are best outside tropical conditions.

Light is a crucial factor in blooming most vandaceous plants. There are three types of vandas: strap-leaved, semi-terete and terete. The first type has broader, flat leaves, while terete types have round, pencil-shaped leaves. The semi-teretes are hybrids between the two, with an intermediate leaf shape. Terete types need full sun, and are best grown in high-light climates. In a greenhouse, give the plants about 25 to 35 percent shade, less in winter if overcast. Leaves should be a medium green, not dark green. In warm, bright climates, you can grow any type of vanda outside (if warm) with partial shade for strap-leaved types and semi-teretes (especially in midday in summer) or inside (when cold) in a bright, south window. In climates where winters are overcast, try ascocendas. Grow them outside in summer and full sun inside during the winter. Be careful to acclimatize plants to avoid burn.

Temperatures for most vandas should be warm; a minimum winter night temperature of 55 F is recommended. Colder spells can be tolerated for a short time if it is not windy. Optimum temperatures are 60 to 70 F at night, and a maximum of 95 F during the day. Warmer temperatures mean faster growth, which must be balanced with higher humidity, air movement, and increased water and fertilizer. Days should be warm and humid for optimum plant growth.

Water should be applied copiously when the plants are growing, but the roots must dry quickly. Because of this, and their extensive root system, they are mostly grown in slatted-wood baskets, or in pots with a coarse potting medium. If their situation is warm and sunny, they may need daily watering. Water sparingly in the winter or during cloudy weather.

Humidity of 80 percent is ideal. In tropical climates this may be easy to obtain. In a greenhouse, this is easier to provide by using an evaporative cooler. In the home, place the plants on trays of gravel partially filled with water. Air movement must be strong.

Fertilize with a balanced (such as 20-20-20) fertilizer applied full strength once a week during warm weather or use a one-quarter-strength solution at every watering. During cool or cloudy weather, apply fertilizer once every two to four weeks. Use a high-phosphorous fertilizer (such as 10-30-20) every third application to promote flowering.

Potting should be done in spring. Plants in baskets do not need to be repotted often. Leave them unless the potting medium breaks down. Set the plants, with the old basket intact, into a container of water to make the aerial roots more pliable, and then set plant and basket into a larger basket. For plants in pots, repot in a slightly larger pot, positioning the plant in the center. Use a coarse medium, whether fir bar, tree fern or charcoal, and work it around the roots. Keep shaded, humid, but drier at the roots until new root tips grow. Do not overpot.    

CYMBIDIUMS

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These Orchids are prized for their long-lasting sprays of flowers, used especially as cut flowers or for corsages in the spring. There are two main types of cymbidiums -- standards and miniatures. Where summer nights are warm (above 70 F), only miniatures can be recommended, because many are more tolerant of heat and able to flower in warmer weather.

Light is important for growing cymbidiums. Coming from cool and bright areas in Asia, they need high summer temperatures, especially at night, may prevent the plants from blooming. The maximum amount of light possible, short of burning, should be given to plants. This means only light shade during the middle of the day, or about 20 percent shade. In cool areas (such as coastal California), full sun is tolerated. Leaves should be a medium to golden green in color, not dark green.

Temperatures are another critical factor in flowering standard and miniature cymbidiums. During the summer, standard cymbidiums are usually grown outside in semishade, where day temperatures should be 75 to 85 F (or more), but night temperatures in the late summer to autumn (August to October) must be 50 to 60 F to initiate flower spikes. Optimum temperatures in winter are 45 to 55 F at night and 65 to 75 F during the day. When plants are in bud, temperatures must be as constant as possible, between 55 and 75 F. Miniatures can stand temperatures five to 10 degrees higher than standards and still flower. Most cymbidiums can tolerate light frosts and survive, but this is not recommended. Bring them inside when temperatures dip to 40 F. In mild climates, they can be grown outside year round. A bright and cool location inside is best for winter months.

Water to provide a constant supply of moisture to cymbidiums, which are semi-terrestrial plants. They generally produce all vegetative growth during the spring and summer and need the most water during that period. Water heavily during the growth season, keeping the potting material evenly moist. Reduce water when the pseudobulbs complete growing in late summer. Keep barely moist during the winter.

Humidity outdoors is usually sufficient during the summer, except in dry climates, where evaporative cooling in a greenhouse is necessary. Keep humidity at 40 to 60 percent during the winter, especially if plants are in bud. Keep the air moving to prevent fungus (Botrytis) from spotting the flower.


Fertilize at the proper time to help cymbidiums flower. During the growth season (spring through late summer), high nitrogen fertilizer (such as 30-10-10) is used. In late summer, use a high-phosphorus, blossom-booster fertilizer (such as 10-30-20), to help form bloom spikes. Fertilize at full strength every week to two weeks. In winter, fertilize once a month.

Potting is usually done in the spring after flowering, usually every two years or when the potting medium decomposes. Shake all of the old potting mix off the roots, dividing the plant if desired. Pick a water-retentive potting mix; medium-grade fir bark with peat moss and perlite is a common mix. Select a pot that will allow for at least two to three years of pseudobulb growth before crowding the pot, while planning on placing the active growing pseudobulb(s) of the division farthest from the side of the pot. Spread the roots over a cone of mix in the bottom of the pot and fill the container with medium, working it among the roots, tamping firmly. Single backbulbs need not even be placed in mix until new growth and roots are noted. Keep shaded and warm until new growth sprouts, and pot as above.

Odontoglossum

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These high-altitude Orchids form the New World Tropics flourish where cool temperatures prevail year round. Odontoglossums are known for their striking sprays of flowers. Culture is similar for hybrids in this group, some being Odontonia, Odontioda and Vuyltekeara.

Light should be bright. In the greenhouse, levels form 2,000 to 5,000 foot-candles are acceptable as long as heat levels can be kept down. If summer day temperatures are high, light levels can be reduced to cool the growing area. While these are not generally considered to be good houseplants, they may succeed at an east window or a shaded south window; western exposures are usually too warm in most climates.

Temperatures must be exacting for these plants. Day temperatures below 75 to 80 F are almost essential year round. Night temperatures of 55 to 58 are best. Short periods of warmer day temperatures may be tolerated, especially if humidity and air movement are at optimal levels, nights are cool and plants have healthy root systems.

Water should be plentiful, coupled with perfect drainage. The potting medium should just begin to dry before watering. This may mean watering every two to seven days, depending on the weather, pot size and material, and type of potting medium. Accordion-pleating on leaves is a symptom of insufficient water or humidity. As with other Orchids from high-rainfall areas, odontoglossums are partially sensitive to poor-quality, which will give poor roots and leaf-tip burn.

Humidity, coupled with moving air, should be ideally 40 to 80 percent. Evaporative cooling in a greenhouse increases humidity while cooling the air and is highly recommended for these Orchids in most climates. Fogging the air or dampening the floor with water also helps cool and humidify. In the home, set the plants on trays above moist pebbles, with the pots resting above the water.

Fertilize regularly with a dilute solution while plants are actively growing. Applications of 30-10-10 formulations twice a month are ideal for plants in a bark-based potting medium. A 20-20-20 formulation should be used on other media. If weather is overcast, applications once a high-phosphorus 10-30-20 blossom-booster formulation as plants approach flowering to increase flower count and substance.

Potting should be done as new growth becomes about half mature, which is usually in the spring or autumn. These plants need to be underpotted, so when repotting leave only enough room for one or two years of new growth. Underpotting also enables the grower to provide the more frequent watering these plants need as the smaller pots dry out more quickly and evenly when filled with roots. A fine-grade potting medium with excellent drainage is required; because the medium is kept moist, annual or biannual repotting is normal. Spread the roots over a cone of potting medium and fill in around the roots with more medium. Firm the potting mix around the roots. Keep humidity high and pot dry until new roots form.
 
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