Orchids do not always reward their pollinators: they sometimes mislead them. From flowers that mimic insects to flowers that smell like rotten fish, orchids have developed remarkable strategies to ensure their reproductive success. Experts from the U.S. Botanical Garden in Washington, D.C., explain how these botanical tricksters work and why, despite their impressive bag of tricks, many orchid species are currently considered endangered.
Mandana Tadayon: Orchids are among the largest plant families on Earth and often trade top spot with daisies as new species are discovered.
George Guenther, advanced gardener, United States Botanic Garden: Orchids are incredibly diverse. There are several thousand species in the world. They have evolved many different forms and growth habits, flowers and things like that, to facilitate pollination and adapt to their environment.
Tadayon: Dubbed “masters of deception” by experts at the American Botanical Garden in Washington, DC, the orchids you are about to see each have a unique trick for attracting pollinators.
#1 Lepanto, Pollination mechanism: Sexual deception
Gunther: This case therefore presents orchids pollinated by sexual deception.
More precisely, the plants that we are currently exhibiting are species of Lepanto.
Certain species of Lepanto Pollination has been observed to occur by pseudocopulation, meaning that in many cases a male fungus gnat, a small midge, visits the flower, thinking it is a mate.
And in doing so, it then transfers pollen when it interacts directly with the reproductive structures of the flower.
#2 Phragmipedium PearceiPollination mechanism: deception by false trap
Gunther: Contrary to popular belief, the pockets present on the flowers are not strictly speaking traps for permanently consuming or catching insects, but they actually participate in their pollination mechanism.
They are often pollinated by insects that visit the flowers, fall into the pockets like a trap, and are unable to return out of the pockets. And so what they have to do is crawl out the back of the flower.
And in doing so, they deposit pollen and then pick up the pollen from that flower when they leave it. The spots specifically on these flowers are meant to mimic aphids. There are small flies whose larvae naturally eat aphids. Flies therefore visit the flowers to lay their eggs among the aphids, then are lured into the traps and must then pollinate the flower on their way out.
#3 Bulbophyllum picturatum, Pollination mechanism: Deception with the scent of rotten meat
Gunther: Bulbophyllum have very interesting pollination mechanisms. Many of them use very strong scents to attract things like flies to their flowers. They can smell like feces, rotten meat, rotten fish, things like that which are really effective at attracting flies.
And when the flies land on the flowers, then they have a little hinged, wavy lip and that lip trips and swings the fly towards the center of the flower, the column, where the reproductive structures are, and then the pollen is thus transferred to the fly from the Bulbophyllum. So, like this Bulbophyllum in this case there is a fairly strong fishy smell. It’s actually even more noticeable on warm, sunny days when you think about active flies.
#4 Coelogyne CristataPollination mechanism: food deception
Gunther: The members of the group Coelogy are sometimes pollinated by food deception. So they have a scent that attracts bees, wasps and other things like that that come to collect the nectar. And sometimes the plants have a little nectar, but they don’t really offer a reward.
They simply trick the insect into arriving.
#5 Spathoglottis KimballianaPollination mechanism: deception of colors and odors
Gunther: This Spathoglottis actually uses bright yellow colors and sweet scents to attract pollinators like bees who will then appear hoping for nectar and will not end up receiving nectar, but will accidentally pollinate the flowers in the process.
And color plays a big role in it. Those bright colors, that bright yellow, are part of the attraction. You will often see bright colors like red, yellow, pink and things like that which contribute to this attraction.
#6 Angraecum of ComoPollination mechanism: deception of night odors
Gunther: These orchids are actually a group of orchids that provide a reward to their pollinators. They are scented at night. They usually smell sweet, sometimes like a rose scent. And the reason they smell that way is actually to attract moths that will visit them at night.
Butterflies use their long proboscis to drink nectar from these long nectar spurs located at the back of the flower. So you can imagine a moth having a little tongue that will extend all the way to the bottom.
There is a famous related species, Hesquipedal Angraecumknown as Darwin’s orchid. Charles Darwin knew this species of orchid.
It carries a 12-inch-long nectary, and Darwin hypothesized that there was a butterfly with a tongue and proboscis long enough to reach the bottom of this nectary to obtain the reward. But during his lifetime, they never discovered the butterfly. It was not until several decades after his death that they discovered a large moth that visits flowers at night in Madagascar and pollinates them, thus validating his theory.
Tadayon: Despite the variety of orchid flowers across the world, many species are considered endangered.
Devin Dotson, Senior Communications Specialist, United States Botanic Garden: Much of this is man-made. One is overharvesting or overharvesting, but a lot of that is habitat loss, right? As things develop, maybe it turns into agriculture, or some other human use for housing or other purposes. Habitat is lost. But the other one will be climate change, right?
I mean, as things change, especially with heat and drought and flooding, those three things have a really big effect on plants. So for things like orchids, if it’s in an area that wouldn’t typically have standing water, it wouldn’t have been flooded or inundated or anything like that. And if this happens repeatedly, all of a sudden, maybe the orchid cannot survive, because it is often underwater.
Or if temperatures change, right, and suddenly summers are even hotter than before, the orchid potentially can no longer survive in that location. Pests and diseases are also affected by climate change, because if there is not very severe frost in some places, maybe the pests and diseases do not die. So pests and diseases can continue to persist throughout the winter into spring. You have larger populations, or they can spread even more because they’re not knocked out by the very cold frosts of winter.
Tadayon: So if you’re traveling and spot beautiful orchids in the wild, experts say the best thing to do is to leave them where they are. Removing orchids from their natural habitat – or attempting to move them across borders – is illegal and endangers already vulnerable species. When orchids are confiscated in illegal trade, some end up at the American Botanic Garden, which has served as a plant rescue center for decades. There, seized orchids are cared for, restored and given a second chance to bloom, helping to protect these remarkable plants for the future.