Invasive Orchids?!

Orchids are notoriously finicky about where they will grow. The family with which they belong (Orchidaceae) is one of the most diverse plant families known along with Asteraceae. Because of this massive diversity, orchids have become quite specialized plants. Orchids hedge their reproductive success on production of millions upon millions of tiny, wind-blown seeds. With seeds so tiny there is not much room left to equip them with food in the form of nutrient packed endosperm (the stuff you are eating when you eat peanuts) and thus orchid seeds rely on very specific species of fungi in order to germinate. Some orchids take this relationship to the extreme but that is a post for another day. Because of all this specialization, orchids are a pretty vulnerable group of plants. Most species are threatened because of poaching and habitat loss and many are endangered. This is why coming across the plant I am writing about is so shocking.

I am talking about the helleborine orchid (Epipactus helleborine) which originally hails from northern Eurasia. I first came across this plant down on some Nature Conservancy land in Gowanda, NY. This was a few years ago and I did not recognize it for what it was. This year however, I began seeing this plant in the strangest places including areas in the City of Buffalo with amazingly poor soil. I was lucky to have a few start growing in my girlfriend's garden so watching them develop was fun and easy. They are a very nice looking plant, standing about 7 to 8 inches high. The flowers are readily recognizable as belonging to an orchid and each plant produces a handful of them per season. The true awesomeness of this species comes from its life history.

In its immature stage this plant germinates and grows as an underground rhizome (underground stem) and is considered fully mycoheterotrophic which means it tricks mycohrrizal species of fungi to associate with it then feeds off of the nutrients that the fungi gain from trees. The orchid can stay in this state of growth for upwards of 10 years before it feels the need to flower. When the right conditions are present it then begins it's adult phase of growth. It throws up a stem, some leaves, and flower buds. At this point it can begin making its own food through photosynthesis but it still uses the fungi as well.

Once it begins to flower it then needs to call on the help of wasps for pollination. There has been some amazing research done on how it achieves this. Apparently the plant begins to release compounds called "green-leaf volatiles" or GLV's. Plants like cabbage produce GLV's when damaged by insects in order to attract wasps that will either lay eggs in/on the insects or use them to feed their young pick them off to bring back to their larvae. Well, when the orchid does produces GLV's, it's doing it for sex. Once the wasps get there they are "encouraged" to stick around a while because the flowers apparently have not evolved structurally sound methods for pollination. Orchids don't dust their pollinators with pollen. Instead they produce pollen sacs known as pollinia that stick to their pollinators via a glue-like substance. There are reports that the flowers produce narcotic drugs and alcohols that dope up the wasps and causes them to linger and stumble around the flower thus increasing the chance of picking up a pollinia. This process then gets repeated every time a wasp visits another flower.

Pretty fracking cool huh? Now, the title of this is a bit misleading. I would not consider this species as truly invasive in that I never see it in any abundance that would suggest it is crowding out native species or changing soil characteristics. I was only able to come across one account of a gardener who claims it grew so thick that he had to eventually rip it out of his garden bed. The jury could still be out though. Not all invasive plants act invasive initially. This plant was first described in Syracuse, NY back in 1879 so it has been here a while. Keep an eye out for it next summer. You will be surprised where you might find it! Also, check out my favorite podcast ever, Wild Ideas, to hear a fun discussion on the helleborine orchid.

Further reading:

http://www.sciencebuff.org/collections/research-collections/botany/helleborine-orchid/

http://link.springer.com/content/pdf/10.1007%2Fs00606-002-0197-x

http://blogs.discovermagazine.com/notrocketscience/2008/05/12/orchid-lures-in-pollinating-wasps-with-promise-of-fresh-meat/#.UOxdL7t0SQ0

http://www.cell.com/current-biology/retrieve/pii/S0960982208005265