CLAN Tropicals

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     From Greek onkos. tumor or swelling -refers to warty callus of the lip.v The genus was established by Olaf Swartz in 1800. Swartz used O. variegatum as the type species for the genus. His original description, of the genus, was published in Kungliga Svenska Vetenskapsakademiens Avhandlingar, Stockholm..

     Oncidium is a very popular genus among orchid hobbyists. With hundreds of species, and thousands of hybrids, available, the Oncidium Alliance has something to satisfy all orchid tastes. In fact, most orchid collections have at least one Oncidium Alliance plant in them. The genus, and members of the alliance, are epiphytic, terrestial, or lithophytic. They have psuedobulbs and are sympodial in growth, with each new growth arising from the previous growth. Plants of this genus range from the diminutive equitants to very large plants. Leaves are distichous (alternating in two opposite ranks), flat and keeled on back side (strap leave), or terete (pencil shaped). The strap leaves vary from very thin ribbon like leaves to the very hard, fleshy leaves. The flowers of most Oncidium species, are generally yellow and brown, although there are a few species with red or maroon. The genus, and members of the Alliance, can be found from the tip of Florida, into the Bahamas, through the Caribbean Islands, and south through Mexico, Central and South America, into Argentina. As can be imagined this wide range leads to a diversity of vegetative and floral form, as well as cultural requirements.

     Besides Oncidium, species and hybrids of the following genera are considered to be members of the Oncidium Alliance: Aspasia, Brassia, Gomesa, Maxillaria, Miltonia, Ornithocephalus, Psychopsis, Psygmorchis, Rodriguezia, Tolumnia, and Zygopetalum. Extensive hybridizing among members of the Alliance has produced a number of man made genera.


     Oncidium Alliance genera grow well in moderate ( Cattleya) light intensity. Direct morning sun is best, until about noon. Observation of the leaf structure can be your best guide to the correct light conditions for which a type is particularly suited. The terete ( ie;"rat-tail" oncidiums Onc.ascedens), or the heavy, fleshy "mule-ears"( Onc. luridum) will tolerate a lot more sun than the ribbony, grass like foliage ( Onc. flexuosum). Light to lime green colored foliage is an indication of proper light. Dark green foliage, while very attractive, is not conducive to the plant reaching it's full blooming potential. Yellow colored foliage indicates too much light. The "mule-ear" Oncidiums will develop a purplish tint to their leaves in higher light, instead of the lime green coloring. The purplish tint indicates proper lighting for these types. Most members of this alliance can be successfully grown, and flowered, under lights. In very mild climates, most members of this alliance can be grown out of doors, with protection from the hot summer sun, and the colder nights of winter.


      The ideal annual temperature range for most members of the Oncidium Alliance are 75°-85°F. (24°-3O° Celsius) during the day and 55°-6O°F. (13°-16° Celsius) at night. Plants will tolerate temperatures to 45°F (10°Celsius) and up to 100°F ( 38° Celsius) for short periods. At higher temperatures, air circulation and humidity must be increased or damage can occur


     Oncidium Alliance enjoy frequent watering, during their growing period, but will not tolerate wet feet for extended periods. However, when growth is completed, a two or three week rest period should follow to allow the growths to mature. Generally speaking, the growing season extends from March to October. The frequency of watering is relative to the container, the temperature, air circulation, and the amount of water retained in medium in the container. Watering should be done, so the roots are approaching dryness, before re watering . In the warmer periods, several waterings a week can be done, without worry, if the roots can dry quickly. The roots are sensitive to fertilizer salt build up, so clear water flushes are necessary for good growth.


     Oncidium Alliance plants should be fed consistently, when in full growth. During the Spring through early Fall, fertilizing every seven days, with several clear waterings in between, will make your Oncidium Alliance plants happy. In the late Fall through Winter, a light feeding once a month will suffice.

     The fertilizer formula should match the potting medium. We recommend non-urea based fertilizers Better Gro fertilizers or Grow Mor fertilizers for tree fern , charcoal , coconut mixes, or various inorganic aggregates medias. Both also have micro nutrients, to provide strength for the new growth, as well as support for the flowers. Non urea fertilizers provide 100% immediately available nitrogen, which urea based fertilizers do not.

     For bark media , use 30-10-10 , which is urea based. The extra urea nitrogen feeds the microbes, which are breaking down the bark. Thereby, not depriving the plant of nitrogen.

      Whichever formula is selected, we recommend half strength at each application. As with most Orchids, Oncidium roots are sensitive to fertilizer salt build up. Oncidiums are particularly fond of organic fertilizers, such as fish emulsion and manure teas. The organic fertilizers eliminate concern of salt build up in the medium.


      Oncidium Alliance do not resent being disturbed, so re potting should be undertaken whenever necessary. The best time is after all flowering has ceased and new growth is just beginning. To minimize root damage, a warm water soak for 10 minutes, will make most roots very pliable and easier to remove from the container.

     While most oncidiums will do well in clay or plastic pots. Some large-growing types such as altissimum, sphacelatum are best grown in a wire or wooden basket.The baskets allow free air flow over the roots, and eliminate over watering problems. Others, such as the equitant ( now Tolumnia) type species and hybrids, and the"rat tail" oncidiums, may be successfully grown on cork bark or tree fern plaques. The equitant also grow well in small clay pot, with out any medium.

     The potting medium must be well-drained, i.e. coarse fir bark, coconut mixes , various inorganic aggregates , tree fern fibers, hardwood charcoal chunks, or pieces of broken pottery, etc. so that the roots can be wet, but then dry quickly. The media supplies only support for the orchid, nothing of a subsistance nature, so anything can be used, as long as it dries quickly. Slow drying media supports fungal infections, such as root rots. Ocassional use of broad based fungicides, such as Dithane M45 or Captan 50% WP helps prevent fungal infections, particularly in fluctuating weather periods, such as fall and spring.

     When dividing Oncidium Alliance plants, always divide into parts with at least four (4) psuedobulbs. Cut into divisions, with very hot shears or knife, then place a dab of fungicide ( Dithane M45 or Captan 50% WP ) paste over the cut areas of each division. Add drops of water to the fungicide powder to make a paste, or use a first aid cream for wounds. Remove any dead roots from the divisions, then lay the divisions aside until new root growth begins. Spray with a fungicide solution over the plant and particularly the root area. At that time, usually a week or so, repot the divisions in their new pots. Now the plants can be watered and fertilized as usual, without worrying about rotting them, because they retained no roots in the division. Newly repotted plants should be placed in slightly lower light for several weeks


     When you purchase a new plant, always place it where you can watch it for a couple of weeks until it is acclimated to your area. Initially, water the plant thoroughly and place it in a bright location with good humidity.

     A preventative spraying of Orthene 75%, wettable powder or in aerosol, on maturing flower buds will prevent thirp damage, as well as aphids and ants. If insects are found on the open flowers, the same chemical can be used to eradicate the infestation, without damaging the flowers. Other insecticides WILL damage the flowers and should not be used. Use Orthene spray as recommended on the label. If using the aerosol, spray from at least a foot away from the flowers. In addition, Orthene 75% does not leave any unsightly residue.

      Examine your plants on a regular basis. Always remove the dried sheathing from psuedobulbs to prevent buildup of moisture, and as a hiding place for insects. In nature, the breezes remove the sheath. In captivity, you must remove the sheath. The removal of the sheath also provides more surface for photosynthesis activity. Insects, particularly scale insects, find Oncidium Alliance plants attractive. Also slugs and snails will dine on these plants. Following the label recommendations on your favorite insecticide will usually solve any insect problem. Neem Oil is a safe alternative to insecticide, and has a pleasant citrus smell. It can be used on Oncidiums in side, or 70% isopropyl alcohol and dish soap make a good alternative insecticide for small outbreaks.

     The Butterfly Orchids, now known as Psychopsis such as Onc. papilo, are successive bloomers. They will continue to bloom from the same inflorescence for several years. At the same time, the Butterfly Orchids will mature additional inflorescences, so do not remove the flowering stem after flowering is completed.


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