It’s the flowering plants (Angiosperms) that dominate rainforest habitats. Evolving to attract pollinators to their nectaries, flower petals act as beacons and landing pads to accommodate flies, bees, birds, bats and more for their carbohydrate-rich nectar reward. The animals hungry for nectar then take parcels or a dusting of pollen between flowers fertilizing the plants. In some flowers, the process of pollination seems perfectly timed and orchestrated supporting its creation by an almighty God (or gods), as there is little else that can explain such accuracy. However, it was also this relationship, such as between an orchid by the name of Angraecum sesquipedale (Darwin’s orchid) and its pollinator, that demonstrated for many people the mechanism of evolution via natural selection. I will mention this example in a little more depth later in the article.
If you’ve heard of it before, Rafflesia is a flower that stays in your mind. The plant is native to tropical southern Asia and includes 16 species. Rafflesia is a parasite lacking its own stem, roots and leaves instead feeding on Tetrastigma vines. The only visible part of the plant is its enormous flower reaching a meter across in the largest species (Rafflesia arnoldii). A seemingly brilliant perfumer for scavengers, it smells like rotting flesh as an attractant, and perhaps its coloration and texture also serve to mimic a dead animal. Flies, and possibly beetles, then visit different flowers transferring pollen and fertilizing the plants. Rafflesia grows in the understory and lives on the shaded floor of tropical forests.
A flower you will know if you’ve ever read On The Origin of Species by Charles Darwin, slipper orchids have a fantastic pollen delivery system. They attract pollinating insects to their slipper, a modified labellum petal (the hollow structure that looks like a water container). As insects search the flower for sugary fluid, they find some around the brim of the labellum. Some then fall into the slipper, which has a coincidentally slippery surface. The pollinating insect, for example a bee, falls in and struggles to escape. Its fate would be sealed if it wasn’t for a channel of hairs that direct the bee up a certain avenue. The bee is forced to walk under a pollen packet (pollinia) that sticks to the bee just before it flies free from the flower. The bee visits other flowers transferring the pollen packet, which leads to fertilization.
The Pahiopedilum genus (pictured) can be found in tropical forests of southern Asia e.g. the Island of Borneo, and usually lives on the forest floor but some are epiphytic. This genus is widely grown among orchid collectors because of its unusual shape, coloration and intricate pollination mechanism.
This is a plant you will be unknowingly familiar with for this is the flower of the vanilla orchid (Vanilla planifolia) where the flavoring is obtained. This is the only orchid used for an edible commercial product. The orchid is thought to originate from the tropical forests of Mexico and here it was used by the Aztecs as a flavoring. There are well known accounts of emperor Montezuma taking chocolatl as his main beverage, which was a mixture of cocoa, chilli and vanilla. You can read more about the cocoa fruit (used to make chocolate) in the article on Amazon Rainforest fruits. The vanilla pods are devoid of flavor and smell when fresh and the flavor emerges only after the pods dry, which can happen on or off the plant. Vanilla orchids have become naturalized and are invasive in different areas including Puerto Rico, the West Indies and South America.
Known as Darwin’s orchid, this plant is famous in the botanical community for its exceptionally long spurs you can make out in the photo above (the long green tubes dangling from the flower). The plant is native to the interesting and mysterious island of Madagascar. They are epiphytic (from the Greek for upon plant) and live on forest trees. Their long spurs contain nectar right at the bottom, and at the time of its discovery, no animal was known that could reach into this ridiculously long spur. Such a creature had to exist because the orchid requires an animal to drink the nectar, so pollinia are attached for fertilization.
Based on his experience and theories about natural selection, Darwin proposed that an animal, probably a moth with an exceptionally long proboscis, had to exist and its identity would be shown in the future. At the time, moths were only known to have probosces as long as their bodies. Darwin’s idea was ridiculed. No such animal was thought to exist, especially not a moth with a ridiculous twenty-something-centimeter long proboscis. Darwin died before learning the existence of the Morgan’s Sphinx hawk moth Xanthopan morgani. And true to his prediction, the moth, with a proboscis of around 9 inches (20 cm), drinks the flower’s nectar and fertilizes the orchid.
Also known as the false bird-of-paradise, Heliconias (Heliconia spp.) are a popular rainforest plant. They include about 40 species native to tropical Central and South America but now grace people’s homes and backyards. The colorful structure you can see is actually a colorful bract (modified leaf), which serves the same function as attractive flower petals. The true flowers are small and seemingly insignificant structures inside the bracts. The bracts also serve to protect the plant’s nectar so only animals that will pollinate the flowers have access, and these are limited to only humming birds and bats.
Saving the biggest flower for last, the titan arum (Amorphophallus titanum) is another flower that smells like decomposing animals similar to the Rafflesia at the top, but the titan arum has a smell of bad fish. The plants lives in Sumatran rainforests and dominate the vegetation in appearance as they grow in forest clearings. The flowers reach three meters tall and three meters across. The giant flowers, which are actually an inflorescence (a cluster of small flowers), only exist for three days every three years.
Sumatran rainforests are being destroyed in a relentless pursuit of deforestation for palm oil. Already, 72% of original forest cover has been destroyed. Deforestation is continuing at an alarming rate and this threatens not only the titan, but the rhinoceros hornbill (Buceros rhinoceros), a major seed distributor, and many many more. It is consumer demand that drives this industry and as consumers we are capable of massive change if we watch the products we buy.
What are your favorite rainforest flowers? Have you visited either the Australasian, Asian, African, or American tropical forests and seen any impressive or interesting flowers? Leave your comments below.