Lawn Orchid, Soldiers Orchid
When I think of Orchids, I think of jungle epiphytes, or exotic fieldtrips, or corsages, or my brother’s flowery greenhouse (and the morons who broke into it recently probably looking for pot, only to leave the doors open in an 8-degree Michigan night).
Or, more botanically speaking, I think of the largest plant family that has splintered itself into maybe 30,000 species famous for specialized habitat niches, dedicated pollinators, restricted fungal associates, and narrow geographic ranges. In short, voted, “least likely to be weeds.”
That “it’s not us” perception seems fundamental to the enormous world trade in Orchids, shuffling the Franken-hybrid and species plants all over the place surprisingly unrestricted and with little thought to potential escape into natural habitats. Too bad that invasive exotic Orchids exist and seem to be getting worse.
Which Orchids dominate the commercial and hobby trade? Answer: The ones with broad tolerances and flexible needs. Same reason so many other exotics have become invasive. And much like the spores of weedy ferns, Orchid seeds are dust blowin’ in the wind. Every warm climate worldwide has Orchid enthusiasts, and cultivated Orchids are getting loose with documented adverse effects, for instance, disease spreading from invasive species to native Orchids. Epipactis helleborine is a good-old weedy species across cool latitudes. Disa bracteata is a self-pollinated nuisance ground Orchid in Australia. And new pests are turning up, perhaps most alarmingly in Hawaii.
Even though most Orchids are too constrained by their local pollinators and fungal associates to venture untended outside their normal ranges, some are self-pollinated or able to form seeds unpollinated. Some find new pollinators, such as the Brazilian Parana Cowhorn Orchid Cyrtopodium flavum (C. polyphyllum) sneaking into Florida aided by an exotic bee (reported in Botany 88: 290. 2010). Some weedy Orchids bring their fungal associates with them, or find new consorts.
My three most recent Orchid encounters in local wild areas were weedy Orchids, probably all non-native species. (The exact nativity of species with dustlike wind-blown seeds, and of weedy species in general can be unclear.) On our class field trip yesterday a sharp-eyed student spotted a pretty Orchid. How nice! At that moment I was unsure of the identity, but at home later with resources in hand, realized it was Eulophia graminea, an invasive Asian species. In the same class, the students had previously spotted Monk Orchid, Oeceoclades maculata, an invasive weedy reportedly alien species CLICK with distinctive blotched (maculata) foliage. This weed extends from Africa (see comments) to Tropical America, and into the Caribbean and Florida. I wonder if Global Warming is helping a northward progression, only a vague hunch. A quick search of the Florida Atlas of Vascular Plants turns up a baker’s dozen non-native Orchids.
The feral Orchid trend continued today. John and George just can’t stay out of Jonathan Dickinson State Park—such a lovely destination in the cool sunshine with Pawpaws, Gallberries, St. Johnsworts, Water Lilies, Silkgrass, and Marsh-Pinks in bloom.
As we stepped out of the car, hey look, an Orchid. Lawn Orchid, Zeuxine strateumatica it was. The invasive exotic Old World species decorates lawns and disturbed moist spots in several southern states. In cultivation it can be medium-magnificent. When escaped, it looks pretty but unassuming.
The species ranges more or less naturally (?) from the Middle East to the Pacific Islands, and has spread beyond. The first U.S. report dates to 1936 near Fellsmere, Florida. Harvard University researchers in the 1940’s (see citation below) surmised speculatively that the Orchid hitchhiked here with imported Centipede Grass around WWI but failed to spread at first because its usual fungal associate was not sufficiently established locally. By almost WWII, the necessary fungus, Rhizoctonia mucoroides, had a local foothold, and the Orchid-fungus duo spread with alacrity. Dig this: The Orchid’s seeds germinate only in the presence of the fungus, which researchers isolated from the Zeuxine in Florida and in its native Java.
Multiple botanists explain Zeuxine’s viable seeds without a known local pollinator as probable self-pollination and/or seed formation without benefit of pollination. Such (apomictic) seeds contain a clone of the mother plant. Determining if the plants self-pollinate or produce seed-borne clones is a feasible student research project.
Lawn Orchid comes and goes mysteriously. John and I often park where we encountered it, but have never seen the little imp there previously. The first time I saw the species was in masses behind a store in Jupiter. It vanished. I wonder if the “here today gone tomorrow” behavior explains Linnaeus’s name, “Orchis strateumatica,” with strateuma in Greek a roving band or regiment of soldiers. The plant’s basic lifestyle explains the peek-a-boo: There is an underground stem rooted at one end, with the opposite end capable of rising up and flowering. After coming up like a periscope, the flowery end dies down out of sight. At that time the fungus presumably sustains the subterranean stem saprophytically until some environmental cue says, “up-periscope.”
An account of the biological side of the Zeuxine strateumatica invasion appears in Mycologia 34: 380-390. 1942.