SPECIAL TOPICS: ORCHIDS

POTTING ORCHIDS

Florida gardeners have a number of choices when considering how their orchids should be grown. Traditionally, plants were grown in osmunda fiber in clay pots. As osmunda became scarce and somewhat expensive, other media such as chopped tree fern fiber, certain bark materials, porous stone (volcanic stone), peat, charcoal and combinations of these materials were used successfully. Plastic pots and other containers have replaced clay in some instances. Experience has shown that most species and hybrids will grow well and produce flowers in any of the above media and pot types by adjusting fertilizer and watering practices. Osmunda fiber and peat have the greater water holding capacity and, therefore, plants grown in these media need to be watered less frequently than those grown in coarser media such as tree fern, stone, charcoal and bark.

Nurseries and retail outlets have a variety of containers from which to choose in addition to clay and plastic pots. Wire and redwood baskets are popular and versatile. Orchids may also be mounted on slabs of tree fern, corkbark, or cypress branches or knees. In many cases, plants may then be suspended from pipework or supports within the growing area or from tree branches outdoors. In frost-free areas, plants may be established on tree trunks.

Repotting is perhaps the least enjoyed chore in the orchid hobby. As a general rule, Cattleyas, Oncidiums, Dendrobiums and Epidendrums need to be repotted every two to three years as the medium decomposes or when new growth extends over the edge of the container. Repotting can be done by transplanting to a larger pot, or by division. When repotting or rejuvenating these orchids, count from the new growth back to four pseudobulbs, cut the rhizome, and remove the clump. This "lead division" is the most vigorously growing part of the plant and will flower within a year after repotting. Back divisions may take several years to attain flowering size; therefore, they are often kept as seconds, traded off to fellow hobbyists, or discarded. To repot, position the plant in a new pot with the oldest pseudobulb touching the back of the pot and fill in with medium around the roots. As a final step, secure the plant with rhizome clips or tie leaves to an upright support.

Phalaenopsis and Vanda require potting less often because of their single-stem growth habit. The decision to repot is made because the plant has become "leggy" or the medium has deteriorated. Tip cuttings of Vandas, including aerial roots, are made and potted in the center of a pot. Potting medium is then placed around the roots.

Raising orchids from seed is both fascinating and rewarding; however, the process requires expertise and special equipment. Orchid seed, unlike seed of other plants, contains no stored food materials; therefore, seed must be germinated on an agar nutrient medium in sterile glass containers. Many commercial orchid nurseries in Florida offer seed germination services to customers.

For more information go to: http://edis.ifas.ufl.edu/EP017
Tips on Growing Orchids in Florida. Robert J. Black.Department of Environmental Horticulture, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date first printed: January 1979. Revised: June 1997


ORCHID CARE

Fertilization is a controversial issue among orchid growers. Many debate the merits of inorganic and organic fertilizers and some even question the need for fertilizer. However, most growers use fertilizer and obtain excellent results.

Soluble fertilizers are dissolved in water and applied in place of a normal watering.Slow release type fertilizers, such as Osmocote, MagAmp, Pro-Gro. etc., release nutrients very slowly, the rate of release being dependent on temperature. Although their initial cost is higher, one application every two to three months is adequate and plants will be continuously fertilized during that time. Additional nitrogen is needed for plants growing in bark.

Watering frequency depends on such factors as pot size and type (plastic or clay), medium, location of the pot (hanging or bench), size of the plant in the pot, air circulation, shade levels, and general environment in the growing area. Saturate each pot so moisture drains from bottom of pot and do not water again until the surface becomes dry. Orchid growers should be aware that water with salt levels in excess of 875 ppm is detrimental to the growth of orchids and should not be used. When salinity level is less than 500 ppm no special precautions are needed. If salt levels range between 525 and 875 ppm, water thoroughly and leach heavily at each watering to wash salts from the medium. Use rainwater by placing large containers under downspouts from roofs.

Most orchids require partial shade for optimum growth and flowering. High light intensities degrade chlorophyll causing the foliage to yellow, and frequently may burn the leaves. Recommended light levels range between 2000 and 3000 footcandles, or 70-80% shade. These shade levels may be obtained by growing plants under saran cloth, growing plants in the shade of trees, shading the greenhouse with whitewash, and growing under eaves of houses. Reed-stem Epidendrums and terete leaved Vandas grow in full sun.

Orchids need to be protected from cold temperatures. Generally 50°F (10°C) is considered the minimum temperature to which tropical orchids can be subjected without exhibiting symptoms of cold damage. Night temperatures of 65-70°F. Few hobbyists are concerned with maximum temperatures. However, if orchids are grown in a greenhouse, be aware that temperatures of 110°F. (43°C) can occur under glass during the hot summer months and two hours exposure to 110°F. (43°C) and 10 minutes to 120°F. (40°C) will burn leaves and flowers.

Orchids, like other plants, are susceptible to a number of insect and disease problems. However, in comparison with other ornamental pot plants, orchids are surprisingly less affected by them. Should pest problems arise, contact your local county extension office for a diagnosis and control.

For more information go to: http://edis.ifas.ufl.edu/EP017
Tips on Growing Orchids in Florida. Robert J. Black.Department of Environmental Horticulture, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date first printed: January 1979. Revised: June 1997