The exquisite “moth orchids” are popular among novice and experienced growers alike. Their beautiful and incredibly long-lasting flowers are borne on easy-to-grow plants, putting phalaenopsis at or near the top of just about everyone’s recommendation list for beginners’ orchids. Most of the phalaenopsis plants offered for sale are hybrids, the results of many generations of breeding from species plants that are native to eastern Asia. The spectacular, winter-flowering white and pink flowers we see most often are the descendants of several species native to the Philippines and other Pacific islands.
In their native habitats, species phalaenopsis grow in moist forests where the temperature remains quite warm most of the year, and both humidity and rainfall are generally high year-round. The plants are epiphytes, growing on shady tree branches.
Advances in hybridizing have produced yellow and red shades as well, although phalaenopsis in these color ranges tend to bloom in the spring and summer, with smaller and less numerous flowers per stem. Some of the smaller-flowered hybrids, particularly those with Phal. violacea in the background, are even fragrant!
Phalaenopsis, like vandas, are monopodial orchids. This means the plants have a single growing point on a stout stem, and new leaves emerge from this single growing point. The leaves are thick and succulent, but because the plants are native to moist forests they have no capacity to store water for dry periods. Unlike cattleyas, which are adapted to distinct moist and dry seasons, phalaenopsis and the closely-related hybrid doritaenopsis need moderate but even moisture and moderate to high humidity at all times.
Potting media – Because phalaenopsis grow best when their roots are moist (not dripping, soggy wet!), potting media for these plants have to be more moisture-retentive than the materials used for potting many other kinds of orchids. Phalaenopsis never want to dry out completely, but they must have good air circulation at the roots. They are epiphytic orchids, remember; in their native habitats their roots are exposed to the air.
Potting media for phalaenopsis should include a generous amount of moisture-holding material such as sphagnum moss. Some growers use sphagnum exclusively, but it is difficult to maintain healthy roots in pots of pure sphagnum moss as the material holds a great deal of water. If the plant is potted too tightly in sphagnum, the roots will smother. Sphagnum should be mixed with other materials that provide air spaces in the pot. For use in plastic pots we mix it 1:1 with expanded clay pellets (Aliflor and Hydroton are two brand names), but you can also use chopped styrofoam peanuts, medium chunks of hardwood charcoal, or some similar material that won’t rot. If we’re potting in clay pots, we mix equal parts of sphagnum, expanded clay and chopped treefern/redwood mix. Before we begin potting, we moisten the mix with water.
You can grow phalaenopsis in either plastic or clay pots. Both have advantages and disadvantages, and the best pot for your plant depends entirely on your growing conditions. Plastic pots dry more slowly than clay pots, so if you use plastic you should not water the plants as often as you would water plants in clay pots. Clay may be preferable for very large plants, as it is heavier and big phalaenopsis can be quite top-heavy, particularly when they’re blooming.
Light – One of the reasons phalaenopsis are popular as indoor plants is their relatively modest light requirements. They will grow, and bloom, with significantly less light than many other orchids and therefore they can be spectacular house plants under the right conditions. You can grow phalaenopsis on a bright windowsill inside the house, as long as the plant is protected from direct sunlight. Their light requirements range from about 750 – 1,000 footcandles at the lowest to nearly 3,000 footcandles. This is about the minimum amount of light necessary for success with cattleyas, but phalaenopsis will not tolerate any direct sunlight. They must be shaded at all times. The plants will grow and flower best with more rather than less light within this range.
Temperature – Phalaenopsis prefer warm temperatures, with a minimum winter night temperature above 60F. A few nights of 60-65F will not harm them, and in fact they often begin their flower spikes as a reaction to a few cool nights. If you have a sheltered spot on your patio, you can put your phalaenopsis outdoors, in the shade, when overnight lows begin to fall into this range. A week or so with these cooler night temperatures may stimulate the plant to begin producing its flower spikes for a spectacular display later in the winter.
Watering and Humidity – When to water? The simple answer: when the potting medium is beginning to dry but before it has actually become dry. Keep the potting medium moist (not wet!). Depending on your conditions, this may be every 3-4 days to once a week or so.
Providing adequate humidity indoors can be a real challenge, but it’s critical to success with phalaenopsis. Neither the plants nor the flowers are happy in dry air. The flowers will last much longer (3-4 months is not uncommon, and 5 months not unheard-of) if the atmosphere around them is adequately humidified. We recommend a minimum of 50% relative humidity. Remember, these are tropical jungle plants! Dry air is the most common cause of bud drop on phalaenopsis.
Problems – Adequate humidity around the plants also reduces the chance of problems with spider mites. These tiny creatures thrive in warm, dry conditions and take a heavy toll on phalaenopsis plants indoors. So-called “humidity trays” have little effect on the moisture in the air. A room or whole-house humidifier will do a better job bringing the moisture level up to a more comfortable level, for you as well as for your plants.
When watering phalaenopsis, it’s important to keep the center growing point, or “crown”, free of moisture. If you accidentally splash or spill water on the plant, blot up the excess with a paper towel so that the crown is dry. If water collects in the crown, it can lead to a fatal fungal infection known as “crown rot”.
Control of overhead watering is one of the main reasons most people grow phalaenopsis indoors. It’s easier to keep the crown of the plant dry and disease-free. An obvious question comes to mind: how do the plants grow in the wet jungle? In their native habitats, phalaenopsis orchids don’t grow in pots with the crown upright. The plants grow attached to trees, with leaves tilted to one side (or even hanging down!) so that rainwater runs off the leaves and does not collect in the crown of the plant. If you can provide the shady, humid conditions these plants love, you can grow phalaenopsis this way in baskets of sphagnum moss, or even mounted on a slab of cork bark or driftwood.
The tall inflorescences we love so much have to be staked and trained. Once the flower spike begins to grow, it’s important that the plant not be moved relative to the light source. The spike will grow towards the light and can develop undesirable twists, kinks and bends if the plant’s position is changed. You’ll also want to stake the spike to help it grow upright, and to support the weight of the flowers. There are a number of staking materials available. We like to use lengths of rigid bamboo, as this looks more natural, but wire stakes work well, too. Use very soft wire or raffia to tie the inflorescence to the stake.
Fertilizing – Most commonly cultivated orchids benefit from regular fertilizing, and phalaenopsis are no exception. They don’t require the heavy feeding that most vandas do, but your phalaenopsis orchids will grow better and bloom better if you fertilize them about twice a month with a balanced, water-soluble fertilizer. We like Jack’s Classic 20-20-20 with minor elements, but any balanced fertilizer will do. To help stimulate roots and flowers, we add 1/4 teaspoon of SuperThrive vitamin/hormone solution to the fertilizer solution, and substitute Jack’s Bloom Booster (10-30-20) formula every third or fourth feeding.
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