Growing Orchids In The Home - University Of Tennessee

Agricultural Extension ServiceThe University of TennesseePB1634Growing Orchidsin the Home1

Table of ContentsGeneral Orchid Culture . 4Light. 4Temperature . 5Water . 5Humidity. 5Air circulation. 6Fertilization. 6Growing Media . 6Repotting . 6Containers . 6Pests and Diseases . 7Insects . 7Fungal and Bacterial Disease. 7Viruses . 7Pest Control . 7Easy-to-Grow Orchids . 8Cattleya . 8Phalaenopsis . 8Paphiopedilum . 9Oncidiums . 9Buying an Orchid . 10Sources. 113

Growing Orchidsin the HomeLinda M Seals, Graduate Research AssistantPaul D. Fortsch., Undergraduate StudentSusan L. Hamilton, Assistant ProfessorDepartment of Ornamental Horticulture and Landscape DesignOrchids are becomingincreasingly popular asflowering houseplants due toimproved cultivars andaffordability. Once considereda rich person’s hobby, orchidsare now more affordable,thanks to recent advances inpropagation techniques. Sincethe first attempt to groworchids in the mid-1700s, theyhave had a reputation for beingdifficult to grow; however,many orchids are as easy togrow as houseplants. Orchidsare quite resilient, and cansurvive many years in the homewith proper care.Orchids are in the familyOrchidaceae (or-kid-ACE-eeee). The orchid family includesmore than 900 genera andabout 25,000 species, makingit one of the largest families offlowering plants in the world.Orchids can be found in nearlyevery environment in theworld. Most of the orchidsgrown in the home are nativeto the tropical and subtropicalareas of South America. Theyare usually epiphytic, meaningthey grow on the sides of4trees, or lithophytic, meaningthey grow on rocks. Orchidsoriginating from temperateregions of the world aregenerally terrestrial, meaningthey grow in the soil.Orchids are valued mostlyfor their exquisite flowers,which are available in a vastarray of colors from tints ofblue, yellow, white, orange andred to almost black. Someblooms are striped or spottedwith intricate combinations ofcolor. The blooms can lastfrom one week to four months,depending on the species.Given the proper growingconditions, some orchids maybloom continuously throughout the year, while others maybloom only once per year.The foliage is usually amedium-green, but someorchids have beautiful leaveswith intricate mottling andvariegation. Many orchids arefragrant. While some may smelllike rotted meat, others havemore pleasant fragrances likelemon, orange, chocolate,hyacinth, cinnamon, wintergreen, watermelon and coconut.GeneralOrchid CultureThe cultural requirementswithin the orchid family varygreatly. The following information is a general guide forplants in the orchid family.Cultural requirements forspecific genera may differslightly.LightThe most common reasonan orchid fails to flower isinadequate light. The plantmay grow and appear healthy,but if there is not sufficientlight, it probably will notbloom. In the horticultureindustry, light intensity ismeasured in footcandles (fc). Abright sunny day outdoorsmight yield 10,000 footcandles. A window indoors,with northern exposure, mightyield as little as 100 fc. Orchids are classified into threegroups according to their lightrequirements: high light (3,000or more fc), medium light(2,000-3,000 fc) and low light(1,200-2,000 fc).

The best place to groworchids in the home is on awindowsill. A south-facingwindow is the ideal location foroptimum results. An eastfacing window would be next,then west and finally a northfacing window. If a windowsilldoes not provide sufficientlight, artificial lighting may beused. For optimum light transmission, clean the windowsfrequently, and clean thefoliage of dust as needed.The plant itself is the bestindicator of proper light levels.If you have not been successful in getting your orchid tobloom, your first suspicionshould be too low light. Orchids that are not gettingsufficient light will be a dull,dark green. Plants that arereceiving sufficient light willhave light to medium greenleaves. Although orchids donot generally receive too muchlight in the home environment,they may become sunburned ifplaced outdoors in direct sun.Sunburn may appear as blackened or yellowish leaves, orleaves which are tinged red.TemperatureTemperature is a criticalelement in forcing orchids tobloom. Orchids are dividedinto four categories accordingto temperature preferences:warm-growing orchids thatprefer winter night temperatures no lower than 60F,intermediate-growing orchidsthat prefer a winter nightrange of 50 - 55Fs, coolgrowing orchids that prefertemperatures no lower than45-50F and hardy orchidsthat can be grown outdoorsyear round.A 10-degree drop intemperature at night is criticalto flowering in most orchids.Plants that are grown underconstant temperatures will notgrow or flower as well as thosegrown with fluctuating temperatures. If the plants aregrown outdoors in the summer, the temperature will dropnaturally. For indoor plants,place the plants in a windowsill where a natural drop intemperature will occur. Plantsgrown under artificial lightingwill naturally receive thetemperature drop as the lightsare turned off in the evening.WaterThe number one cause ofdeath in houseplants isoverwatering. Orchids are noexception. Most orchids preferthe growing media to drybetween waterings. There areseveral methods to determinewhen a plant needs watering.Insert your finger about 1 inchinto the soil near the center ofthe container. If the soil feelsdry, the plant needs water; if itis wet, wait. You can also pickup the pots to compare theweight of a dry pot versus awet pot. The pot will be lighterwhen it is dry. It is better tosoak the plant thoroughly andoccasionally than to waterfrequently with small amountsof water. To thoroughly wateran orchid, place it in a sinkand add lukewarm water untilthe water runs freely from thebottom of the pot. Avoid usingcold water (below 50F), sincethis can damage roots and cankill root hairs. About twice ayear, put your plants in theshower, and run warm waterover them for several minutesto clean the dust off thefoliage.HumidityOrchids love humidconditions. They prefer a rangeof 50-70 percent relativehumidity. There are severalways to increase the humidityin the orchid’s environment.The simplest method is toplace several plants closetogether to increase the humidity of the air surrounding theorchids. Plants can also beplaced on trays containing alayer of pebbles or small gravel(Figure 1). Fill the tray with justenough water to fill the spacesbetween the gravel particles.The water in the gravel willincrease the humidity. Neverallow orchids to sit directly inwater, since this can cause rootdisease. You can also increasethe humidity by placing theplants in a bathroom window,by using plastic containersinstead of clay pots, or you canFigure 1. Increase the humiditysurrounding a plant by placingit on a tray of gravel. Fill thetray with enough water to fill inthe spaces between the gravel.5

purchase a humidifier. Airconditioners and heaters drythe air, so avoid placing orchids near vents or ducts.Air CirculationAir movement is alsoimportant to grow orchidssuccessfully. Air movementhelps to decrease the incidenceof fungus diseases and bacteria, and it aids in supplyingcarbon dioxide, which is necessary for the plant to photosynthesize. Most orchids placed ina windowsill will receive adequate air circulation.FertilizationFertilizer requirements fororchids depend largely on thetype of plant being grown, andthe type of growing media inwhich the orchid is growing. Agood general rule is to applyfertilizer once a week while theplant is producing new growth.As the new growth begins tomature, decrease fertilization.Discontinue fertilizing entirelywhen the plants becomedormant, or stop producingnew growth. A good practiceis to water at least once amonth with plain water toprevent root burn from overfertilization.Specially formulatedorchid fertilizers are availablethat are already diluted. Followthe label directions exactlywhen using orchid fertilizers.Equally balanced fertilizerssuch as 10-10-10 or 12-12-12can also be used, but thesefertilizers must be diluted toone-quarter strength beforeapplication. Orchids planted inbark require higher nitrogenrates than plants in othergrowing medias, so a ratio of620-10-10 or 30-10-10 fertilizeris recommended.Growing MediaDrainage and aeration arethe two most important factors to consider when choosing a growing mix. Specialblended media can be purchased at most retail gardencenters for growing orchids.These mixes contain fir bark,peat moss and either perlite orvermiculite. Many orchidgrowers prefer mixing theirown growing mix. There areseveral types of growing mediato choose from, such as treefern, redwood bark, cork,sphagnum peat moss, Osmunda, charcoal, Rockwool,polystyrene foam, rock cultureand sand. The growing mediaused is a personal preference,depending upon growingconditions and environmentalfactors of the grower.RepottingMost orchids should berepotted every one to twoyears, although some varietiescan go years withoutrepotting. Timing isthe most criticalelement in repottingorchids. If orchids arenot repotted at thecorrect time, floweringmay not occur until thenext year. Nearly all repottingshould be done betweenFebruary and June. This is thetime when most orchidsproduce new growth and newroots. This usually occurs justafter the plant flowers. (Plantsthat grow actively year roundcan be repotted anytime.)While the plant is out ofthe container, clean away all ofthe old growing media andrinse the roots under tepidwater. Before repotting, trimoff any dead roots, dead oryellowed foliage, dead flowerspikes and dead or rottingpsuedobulbs (a thickened stemon some types of orchids thatis used to store water). Replantthe base or the crown of theorchid at the same level it wasgrowing prior to repotting. Toavoid spreading pests anddisease, use a clean workplace,sterile pots, sterile growingmedia and never transfer soilfrom one plant to another.ContainersDrainage is one of themost important factors toconsider when selectingcontainers for your orchids.Containers designed especiallyfor orchids have slits down theside for added drainage (Figure2). Some containers havedrainage holes in the bottomof the pot. If these holes aretoo small, they can be enlarged. Clay and plastic are themost popular materials forFigure 2. Orchid container withside slits for added drainage.