Ecology of the Phalaenopsis orchid
Phalaenopsis (the genus) hails from greater Southeast Asia, from Southern China and India through the Indonesian islands to Australia. Phalaenopsis amabilis (the ancestor to most common grocery store orchid plants) originally hails from just the islands, south through to Australia. These plants are epiphytes, typically growing on trees in low elevations up to about 600m. This species grows higher up on the tree, and typically is partially exposed to scattered direct sun, or part direct sun for a short amount of time in the day. As such, it has thicker leaves and roots compared to other Phals.
This (and many other Phalaenopsis) is a CAM plant, which means that it has a modified form of photosynthesis to allow it to better survive hot temperatures and frequent desiccation. In this form of photosynthesis, the stomata (pores) of the plant are only open at night where carbon dioxide (CO2) is taken in, and oxygen (O2) is released. The CO2 is then stored as malic acid inside the palisade cells of the leaves. When day breaks, all the stomata close, sealing the plant tight. You can think of this as the plant holding its breath during the day, and releasing its breath at night. Because the stomata are closed, it’s difficult for water to escape, so it helps the plant conserve water (and prevent photooxidation, which I’ll talk about in a future article). These types of plants typically resist drying out better than C3 (regular) photosynthesis plants. As an epiphyte with exposed roots, it makes sense why the plant evolved this mechanism.
The species, Phalaenopsis amabilis, was discovered to science on the island of Ambon, which is one of the Spice Islands by German naturalist Georg Everhard Rumpf. Rumpf, also known in Latin as Rumphius, he came to Ambon in conjunction with the Dutch East India Company as a merchant, became a permanent resident of the island, and occupied himself with describing plants on the island. Even though his life was beset with misfortune (he went blind in his 40s, and his first wife and children died in an earthquake while he was outside a shop and they were inside), he was a master of multiple languages, and loved to play with words when describing plants and animals.
One could argue that his blindness aided his linguistics, but he was still clever before his blindness. He was an inquisitive man who loved the local cultures of the island, and published official botanical descriptions of plants in his native Javanese, Latin, Chinese, Malay, Portuguese, Hindi, and others. His magnam opus was Het Amboinsche kruidboek or Herbarium Amboinense, a catalogue of the plants of the island of Amboina. He had described the orchid before the Linnaean binomial system was created, and called the plant, Angraecum albus majus in 1750. Later, it was reclassified by Linnaeus, and eventually by Carl Ludwig Blume in 1825 to the name we know it by today – Phalaenopsis amabilis. The specific epithet, amabilis, means “fair” (in a pretty sense) or “friendly/appeasing/lovely”.
Nowadays, the generic orchids that you see in grocery stores are complex hybrids of this species. In many of the miniatures, Phalaenopsis violacea and related species are used to reduce the size of the plant. Some of these have been so heavily hybridized that most of what you buy are polyploid plants (plants with duplicate sets of chromosomes to make them bigger and more vigorous). In plants, polyploidy is beneficial, whereas in animals, it is detrimental. Polyploid plants have multiple times the genetic material, and therefore have multiple times the gusto to handle whatever comes at them – within their original parameters, of course!
The most common questions that I get with regards to Phalaenopsis orchids are “is my orchid dead” and “how can I make my orchid bloom again?”. Let’s hit one at a time:
“How can I make my orchid bloom again?”
The Phalaenopsis species that they use to make the commercial hybrids that you buy in stores actually hail from cooler tropical highland environments. (Knowing about where a plant comes from will help you become more successful with plants!) When seasons change in those environments, you get variance in day/night temperatures and moisture cues that help the plants know it’s time to bloom. The Philippines is an excellent example of the tropical highland, and tropical savannah climate that many Phal species hail from, and I will speak about it in very broad strokes.
In a tropical savannah climate, there is a distinct wet and dry season. Because there is little rainfall during the dry season, there is little water in the air to help regulate the air temperature. Thus, you get more unstable temperatures, and a drop in nighttime temperatures (there is not enough water in the air to hold the residual heat from the sun to keep the night warm).
This all triggers the Phalaenopsis – a consistent drop in temperatures coupled with some mild dryness. As you’ll see from the Philippines climate, the dry season is short, and much of the Philippines aren’t completely dry through the dry season. However, the temperature will flux enough to drop low enough to initiate flower spike formation. While conventional wisdom holds that cool nights initiate Phalaenopsis to set spikes, according to Blanchard and Runckle (2006), cooler day temperatures actually initiate spike formation. This is consistent with temperature drops during the dry season. They found that hot temperatures >25C actually inhibited flower formation, and increased foliage and plant growth. This makes sense for the plant, as it will want to maximize favorable conditions to build itself up and save energy for reproduction. Generally-speaking, many plants follow this trend (but some follow the complete opposite for other reasons… more on that in another article) where they emphasize asexual reproduction or vegetative growth when conditions are favorable, and sexual reproduction when conditions falter or become less favorable.
To put numbers to this, let me quote them:
“After 20 weeks, ≥80% of plants … had a visible inflorescence when grown at constant 14, 17, 20, or 23 °C and at fluctuating day/night temperatures of 20/14 °C or 23/17 °C. None of the plants were reproductive within 20 weeks when grown at a constant 29 °C or at 29/17 °C or 29/23 °C day/night temperature regimens.”
Additionally, later, according to Runckle (2018), even as little as 8h of exposure to unfavorable high temperatures will prevent spike formation in many hybrids. However, once spikes have been formed, increase in heat will actually help the flowers form faster! But a candle that burns twice as hot, burns half as long… warmer temperatures will indeed make the flowers form faster, but they will not hold on the plant as long – in warmer tmeperatures, the plant wants to focus on vegetative and asexual growth. It’s even been rumored that a flower spike will form into a keiki instead of flowers if the temperatures are too hot, although this has not been fully confirmed, as there is no consistent way to test this (keikis are not formed consistently).
Either way, Phalaenopsis will spike at the 3rd or 4th node (usually below the 3rd or 4th leaf) of the plant, and Phalaenopsis schilleriana requires short days to bloom (Not that the average person would happen upon this species, but it is occasionally used in hybridization, so this requirement might throw a wrench into blooming).
Sakanishi et al. (1980) found that Phalaenopsis amabilis was more floriferous in short day photoperiods (meaning that it makes more flowers when the days are short). This could be passed off into the hybrids that are sold in stores.
So, In short, to make your Phalaenopsis bloom, it needs consistently cooler (remember, if your plant or room gets direct sun, there may be warmer microclimates, so beware of that) temperatures <25C/77F consistently for 2 months to bloom with less-frequent waterings. Remember, your house may heat up more in the day than you think, so beware of that!
“Is my orchid dead?”
Let me be frank… just because your orchid drops flowers DOES NOT mean that it is dead. Flowers come and go, but the green part of the plant is forever. Yes, that’s the actual plant. So, if you treat the green part with the floppy leaves well, it will reward you with more flowers. If it’s super wrinkled, splash water on it more (it’s dehydrated). More on this later. Remember, unless it’s yellow or brown, it’s ALIVE!
Phalaenopsis Orchid General Care
Light (indoors) – Bright ambient light with a tickle of sun. A northeast, east, northwest, or west window is best for them.
Light (outdoors/greenhouse) – Place in full shade
Temperature – The cooler growing hybrids can grow up to 30C/86F, but will focus on foliage at higher temperatures >25C/77F. Some species like Phalaenopsis celebensis will not care about temperature, but rather water availability to bloom. They will tolerate down to 15C/59F before taking damage. Many folks put them outside in the spring and fall to get that cool weather to bloom.
Watering (indoors/greenhouse) – They are epiphytes, so they like fast wet-dry cycles, but like to dry completely between waterings. Soak/saturate the plant, aerial roots, and media in the sink/shower with warm water 2-3x a week except in the winter (Dec-Feb), reduce watering to 1X a week. Spritz daily regardless of season. Tap water is fine unless you have super hard water, in which case, just use rainwater.
Watering (outdoors/greenhouse) – daily; multiple times daily in the heat of summer.
Media (indoors) – Depending on how dry your conditions, anything from pure sphagnum in a clear plastic pot to fine orchid bark mix in a clear plastic pot (bark mix preferred)
Media (outdoors/greenhouse) – coarse bark chips in terracotta
Troubleshooting your orchid
Leaves are wrinkly – usually one of two causes, each of which starts at opposite extremes, but both end up at the same result. Either the plant is underwatered (usually roots will be wrinkly too, still green, and leaves will be floppy), or the plant has root rot from staying too wet. If the plants roots have rotted away, they will be brown/black and when you feel them, they will be hollow, and may even smell.
Irregular spots – uncommon, but can be bacterial spot. Just keep the leaves dry, and if it spreads, treat with Physan
Black tips – salt or fertilizer burn. Flush with lots of water mixed with lemon juice, and use softer water to water your orchid. Rainwater is ideal.
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Sakanishi, Yoshihiro; Imanishi, Hideo; Ishida, Genjiro; Effect of Temperature on Growth and Flowering of Phalaenopsis amabilis 1980 Bull. Univ. Osaka Pref., Ser. B, Vol 32