One orchid, two orchid, red orchid, blue orchid!
Learn about dirty tricks and rare beauty, as we stroll together through knowledge and Orchid Gardens.
Written by: Erin Aiello
Photos, video and drawings attributed to Erin Aiello
Orchids are quite the attention grabbers, wouldn’t you agree? From their diverse flowers and growth habits, to their pollinator mimicry (and trickery!), and to their obligatory fungal mutualisms and parasitisms, orchids never fail to fascinate. I study mycorrhizae, the relationship between plants and the mutualistic fungi on their roots. Naturally, when I heard that orchids rely on, and sometimes parasitize their mycorrhizal fungi, my love for these beautiful plants deepened.
Today, I’m going to share my love of orchids with you. I’ll share with you what I’ve learned about some of the tricks they have up their sheaths. That includes how they trick pollinators in order to ensure pollination of their flowers, and how they sometimes parasitize fungi. I’ll tell you about orchids and their symbiotic mycorrhizae, and I’ll share with you an Orchidaceae treasure trove that I stumbled upon while visiting a friend near San Francisco.
Let’s start with the obvious: those rad-iculous flowers. Most orchids have a closely-knit relationship with one specific pollinator per species; such that the orchid’s flowers have evolved to look like a receptive female of its pollinator species. This lures the male in, to “mate” with the bottom “lip” of the flower, or the labellum, which often looks like the abdomen of an insect pollinator. Upon leaving, the pollinator pulls back on a part of the flower that encapsulates its pollen on the ends of little stalks. The stalks and the pollen together are called pollinia, each being a pollinium. At the base of the pollinia is a home-made super glue. When the pollinator pulls out of the flower, the cap of the pollinia pops off, trickering the flower to snap back, fling forward, and -SMACK- stick its pollinia to the pollinator, usually on the head or thorax. This forces the pollinator to carry the orchid’s pollen to the next flower, which the pollinator thinks is a receptive female. He then transfers the pollen to the female parts of that next flower, pollinating the orchid. This interaction increases orchid sexual reproduction and quite the opposite for the bee. Below is an example of what I call the pollinia trick, using a bee that was found dead in a greenhouse. This bee is not this orchid’s pollinator.
See the pollinia glued to the bee’s head? And how as soon as the cap pops off, the pollinia are stuck to the bee? This is a very fast and effective mechanism.
Orchids have different modes of reproduction; they reproduce asexually by creating new clone plants along their underground stems, which eventually break off as the stems decay. Some orchids produce flowers that never open, but pollinate themselves. This is called cleistogamy. Those orchids that require pollinators often coevolve with one pollinator species; meaning that the pollinator drives the evolution of the orchid, and sometimes the orchid drives the evolution of its pollinator. For the pollinia trick, the labellum evolves to look like its most common pollinator. For another example of the pollinators driving the evolution of orchid: the modified labellum (lower petal) of the lady’s slipper orchid looks like a big bowl – maybe a nice place for a bee to rest. However, this bowl has directional trichomes (like plant hairs), which guide the bee toward the flower’s sexual organs, where the bee can escape. The bee can’t escape any other way, so by being guided by the orchid, this increases the orchid’s reproductive success. Another example is given by Darwin’s orchid, which has a long spur (modified petal) with nectar at the base. A moth with a long probiscis (long, skinny tongue) is able to drink the nectar without rubbing against the pollen of the flower. Eventually, the orchid evolves to have a longer spur so that the nectar reward is harder to reach, and the moth brushes against pollen and pollinates the next flower. In turn, the moth evolves to have a longer probiscis in order to reach the nectar more easily. The two drive one another’s evolution, and these traits become more and more extreme.
Let’s take a walk through Shelldance Orchid Gardens, and consider what mode of reproduction might be dominant for these different species, and if they’re pollinator-dependent, what kinds of pollinators they might have.
In a quiet beach town just south of San Francisco, on a hill overlooking cypress trees and the ocean, sits a modest cluster of greenhouses, a small shop, and a friendly cat.
From the outside, Shelldance looks like it began as a tiny home that, over many, many years, accumulated “add-ons” (very large greehouses), wherever they might fit.
…but then you step inside, and suddenly you’re in a walking meditation. Row upon row of orchids fill your eyes and take your breath away.
Shelldance has two large greenhouses filled to the brim with orchids, bromeliads and air plants. Here are photos of some of my favorites.