Asahi image Copyright Evelyn Drew

Phalaenopsis Orchids
Phalaenopsis Flasks, Plug Trays & Flowering Plants

Phalaenopsis Culture at a Glance

Light: About 800-1500 foot-candles
Temperature: 63°F night, 78°F day
Humidity: 50% - 80%
Watering: Do not allow to dry completely
(Water once or twice a week.)
Feeding: Once a week (at half strength)

Orchids love Air Movement. The higher in the arboreal environment the plants ancestors evolved in, the greater the plants need for air movement. Most Phalaenopsis benefit from a great deal of air movement. The best way to kill Phals is to try and grow them where there is insufficient air movement. Phals "like" to expire from "crown-rot". Crown-rot is a condition where water gets into the crown of the plant (where the leaves originate from), and allows an opportunistic bacterium to get activated, and into the plant. Sometimes plants can turn to goo overnight. The best way to keep this from happening, is to make sure that you have adequate air movement. An oscillating fan in your plant growing area should be sufficient if you do not have too many plants. I use three 22-inch box fans, and my heater fan runs continuously, in a 1400 square foot greenhouse. Everything sways in the breeze, and I can water almost any sunny day, and the plants will be dry by nightfall.

Phals need fairly LOW LIGHT, (800-1500 f.c.), or about the same light required for African violets. NEVER let your Phal get direct sun on it, it will take only a few minutes for the sun to kill or severely damage your plant. Set your plant NEAR a bright window so it can benefit from the bright, INDIRECT light. Phals can also be very successfully grown under artificial light. WAY too much light causes white, dried, burned areas on the leaf. Too much light makes small narrow stout leaves that are bleached light green or flushed with red (plain green leaf types) or purple (mottled leaves and pinks), and have short flower spikes, with few, small, hard flowers having washed-out color. Lower light levels allow the leaves to become wider, and medium green. Not enough light makes weak, flaccid, dark green plants that do not grow well or bloom. An increase in light is essential to flower spike induction. Lower light levels during the last stages of bud development are needed for the largest blooms of the best color. Light is probably the single most important factor in producing flowers. I vary the light my Phals get throughout the year. During the winter, I have virtually no shade on my fiberglass greenhouse, in Spring and Fall, I use 40% shade, in early Summer 80% shade, and in late Summer probably close to 90% shade. This moderates my cooling costs during the summer, and the plants get more leaf area that then gets used to store more energy later when the light gets increased. When you grow Phals in a house, remember that the sun gets lower to the horizon during the winter, and can come much further into southern-facing rooms. Mid-winter sun is not very dangerous, but you can easily sunburn Phals in Spring and Fall if you don't watch where the sun is coming in.

While most people recommend growing Phals at 65 or warmer, we have good results maintaining a 60 DEGREE F NIGHT temp, year- around, and a DAYTIME MAXIMUN HIGH of about 90 DEGREES F. During the growing season the temperature pretty much oscillates between the extremes going down to 60 almost every night and going up to 80 almost every day, sometimes up to 90 in the summer. Generally, don’t grow them at less than a 60 degree F night temp, and don’t allow daytime temps to exceed 90 degrees F. Phal plants will not be harmed by occasional temps over 100, but the flowers will not last very long. Try to keep the differential between the day and night temps to less than 20 degrees, (ie:60 night , 80 day, or 65 night & 85 day). A one to three week period of nights in the upper 50's can help induce flower spikes. I have "successfully" (less than 5% loss) grown Phalaenopsis down into the 40's; these were large, strong plants. Some got bacterial infections and expired, but most had unbelievable amounts of flowers when the temps came back up again. I don't recommend growing Phals below 60 unless you have enough experience to know what you are doing, and are willing to lose a few plants that simply will not tolerate the cold.

Orchids need to have high humidity. In a home with forced-air heat, or other dryness problems, grow your orchids with other plants, and/or over wet gravel trays. With higher temperatures keep humidity higher, (around 75-80%) with lower temps keep humidity lower, (around 40-50%). Over watering does not compensate for low humidity. When Phal flowers are developing, higher humidity increases the size and quality of the shape of the flowers; however, too high of humidity causes the flowers to prematurely age when removed from the greenhouse, and increases the probability of fungal spots on the flowers.

The best thing to do when learning to water orchids is to think of where they grow in nature. Phals live in trees where they get constant fresh air movement around their leaves and roots. Frequent light rains percolate through the organic matter above, bringing nourishment to the roots. However the air movement allows the plant to dry rapidly, avoiding bacterial problems. When we stick most of the plant's roots into a dark pot with a bunch of medium in it, it can be quite a challenge to approximate the conditions the plants ancestors evolved in. Generally, WATER HEAVILY when you water TO THOROUGHLY FLUSH OUT SALTS from water and fertilizer, then let the medium ALMOST DRY OUT before watering again. One of the best ways to tell the amount of moisture present without taking the plant out of the pot is to develop a feel for how much the pot WEIGHS, medium like bark or moss is rather light when dry, so a plant usually feels top heavy and the pot feels obviously light. Correctly watered plants will have plump silvery roots with green or amber tips. NEVER use chemically softened water on orchids.

In my greenhouse, I feed continuously most of the year with quarter-strength 20-20-20. However, for those growing in the house, or without a fertilizer injector, it is much easier to use half-strength fertilizer every other watering. Feeding depends upon some other environmental factors: the brighter the light, the more food is required; the more food that is available at the roots, the more water is necessary to prevent salt-damage to the roots; and to some degree, the higher the temperature the more food is required. So, basically if you grow brighter and warmer, you need to water and feed more, and if you grow under lower light and temperature, you should water and feed less. Stick to a “balanced” formula of fertilizer unless you know what you are doing, (balanced means all three macro nutrients, Nitrogen, Phosphorus, Potassium are represented by the same number in the formulation, (ie:14-14-14, 20-20-20, etc.)). It has been shown that Phals will flower very well with no change in feeding, although if you can "fatten them up" right before spike induction with a high Phosphorus fertilizer (10-50-10 or something similar), you can get increased flower counts. Magnesium Sulfate (Epsom Salts) has been used by some West-Coast Phal growers for years, prior to spike induction, and it really does seem to help form dramatic inflorescenses. The Magnesium will bind up Nitrogen, so it is best to use by itself or in conjunction with high-phosphorus fertilizer if you use it.

Phals are one of the easiest orchids to grow and bloom in the home. Most Phals will bloom without being “forced”. However if you have a MATURE Phal that is growing well, but hasn’t bloomed, it might need to be coaxed into bloom by lowering the night temp to about 55 degrees F for about one or two weeks, (in fall/winter if a winter/spring bloomer, or in spring if a summer bloomer), while simultaneously increasing the light level to about 1,500 foot-candles. If you already grow your Phals on the cool side, just increasing the light will probably bring them into bloom. You can control spike induction in most Phals fairly well with temperature. If you keep the night temp at 65 or above, and let the day temp go over 85 every day, under conditions of relatively low light, Phals will grow and grow and not many of them will flower. If you lower the temp to 60 or lower at night, and keep it below 85 during the day, while increasing the light level, you will spike almost everything that is capable of doing so.

If the medium stays soggy in the bottom of the pot and never quite dries out all the way, it is probably time to repot the plant. Phals love to be repotted. Let me rephrase that: once you learn to repot them with some care, they respond very well to repotting. Young Phals can be repotted every 6 months as they outgrow their containers, average size Phals should be repotted every 18 to 24 months, depending on your media and how heavily you water. The best time to repot is when you can see new root growth, but Phals planted in New Zealand Sphagnum can usually be repotted almost any time of year. To repot a Phal with "some care", the idea is to disturb the healthy roots as little as possible, while trimming off the rotted or water-soaked roots. Don't pull on the roots to remove the dead parts, CUT them off with a sterile tool. If you pull the roots, they will become cracked and damaged, and you may lose them when you start watering again. Don't try to pry every single piece of medium off the roots, it will result in damage, it is better to leave some of the old medium than to damage the roots. Carefully put new media into the pot, and around the roots. It is a good idea to use a new pot, or clean the current pot if you are going to reuse it. Withold water for a week or two, to allow the plant to heal any root damage, and prepare to start a new flush of root growth. When you see new roots, water as normal. Plants without roots need additional humidity; and a shot of vitamin B (Superthrive works great) will help start a new flush of roots. It is also a good idea to use slightly tighter (smaller particle size) media for run-down plants; grow them like seedlings in lower light, and higher humidity.

People frequently ask what to do when their Phal has lost its flowers. Well, as in most cases there are two schools of thought on this. We decide whether to get the best blooming we can on the next blooming, (remove entire spike, “pump-up” plant), or to keep the plant blooming as long as possible at the expense of next seasons blooming, (to make a hybrid, or just appreciate the flowers). To get continuous blooming cut the spike just below the first node that produced a flower, and a branch will probably form from the node below where you cut. DO THIS ONLY ON MATURE PLANTS! Usually plants in six inch pots are safe candidates for this treatment. Some species such as amboinensis, cochlearis, fasciata, lueddemanniana, sumatrana, violacea, and their hybrids have spikes that will persist for years, DON’T remove these, if you leave them on the plant they will probably continue to flower each year for a few years before being replaced by new spikes.

A complete treatment of Pests and Diseases of Phalaenopsis is really beyond the scope of this document, however, I will try to give an overview for the sake of the beginners in the audience. The PESTS that you are most likely to see on your Phalaenopsis are: Mealybugs, Scale, Mites, Molluscs, Thrips, Aphids and Rodents. Most people will never have trouble with all of these, but just a couple. I recommend that you talk with other growers in your area about what they use to control a particular pest. The best advice for beginners is: ALWAYS QUARRANTINE NEW PLANTS. When you bring home a new plant, do not set it amongst your other plants. Set it aside for at least two weeks, and watch for pests. This is the SINGLE most important thing that you can learn about pest control. After you have infested your entire collection with with a pest from a new plant, and then have to clean and repot your entire collection to erradicate it, you will remember ... it really takes the fun out of buying orchids. DISEASES can be vectored by PESTS, so you particularly want to keep the known vectors under control: they are Thrips and Aphids, although there is risk that any sucking insect that moves from plant to plant during feeding may vector virus. Orchids cannot be cured of virus. Virus may make the plant grow and flower with less enthusiasm. Virus can also be transmitted to your other plants, some of which you may wish to keep virus-free. I like to keep spray bottles of Alcohol in the greenhouse for immediate spot-treatment of pests when I see them. While Phalaenopsis are susceptible to many bacterial and fungal diseases, by far the most ubiquitous killer of Phalaenopsis is Pseudomonas. Pseudomonas is a genus of bacteria that frequently causes the dreaded crown-rot of Phalaenopsis. Pysan (and other quarternary ammonium compounds, like RD20) are VERY effective against Pseudomonas. As little as 100 p.p.m. (p.p.m. = parts per million; 1 tsp Physan 20/1 gal water = ~ 1,000 p.p.m.) of quaternary ammonium can control Pseudomonas very well. Physan is a contact material, not systemic, and it lasts no longer than a couple days. You should use it at a high concentration to keep your growing area clean, and use it periodically on your plants at a lower concentration, to prevent crown-rot.

Try “How to Grow Orchids”, a Sunset Book that is very informative, has very good color pictures, and is very inexpensive. For the serious orchidist, try “Home Orchid Growing” by Rebecca Tyson Northen.


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Robert Bedard Horticulture • Scotts Valley, CA • (831) 439-9484
All content ©2004 by Robert Bedard. Last update: 12/16/04
Dtps. Asahi Image Copyright Evelyn Jenkins Drew