Field Notes--Orchids & Sundews of Tallulah Gorge

Tallulah River as seen from the hydroelectric station.

October 14, 2011

It is just dawn and I am riding in the back seat of the Atlanta Botanical Garden’s Subaru heading toward Tallulah State Park. The conversation up front is making me want to climb out the window.  Matt Richards and Ron Determann, ABG’s Conservatory Director, are talking about the ecological losses Ron has witnessed in 30 years of plant conservation. 

“There aren’t really any natural areas left in Georgia.  Not really,” he says. “Just pockets with refugia of rare plants.”

The main problem, as he sees it, is the heavy use of herbicides used to control weeds along roadsides, under powerlines, and even along paths in natural areas visited by the public.  The method formerly used, which is less destructive, is mowing.   But that takes more people and equipment, plus you have to mow more often than spray—at least initially.  The result, according to Ron, has been the destruction of most roadside ecology. 

Sarracenia leucophylla, Conservation Garden @ ABG

Now, you might not think that native plants, and certainly not rare plants, grow in highway medians or under powerlines, but they do. The white-top pitcher plant (Sarracenia leucophylla) was thought to be extinct in Georgia until it was found growing in a powerline right-of-way in 2000.[i]  Similarly, one of the few Georgia populations of Tennessee yellow-eyed grass (Xyris tennesseensis) clings to the greenspace in a highway off ramp.[ii]   

As counter-intuitive as it seems,  nutrient-poor sites also harbor greater biodiversity.  Repeatedly spraying for weeds builds up decaying vegetation, which enriches the soil making it more hospitable for weedy growth.  So instead of a diverse roadside ecology, you get a few species of invasive weeds growing lush and tall.  Naturally, the invigorated weeds require more frequent of spraying.  And so it goes.

The other nasty side-effect of using herbicides is the harm they can do to amphibians.  Herbicides with surfactants are not to be used in wetlands, but they very often are.  The surfactants clog the breathing pores of frogs and other creatures, killing them.

In addition to weed suppression, herbicides are injected into tree stumps to prevent re-sprouting.  The practice is thought to be safe for the creatures that live around these stumps, but Ron doesn’t think so.  He describes finding skeletons of 30 year-old bog turtles that died after stumps around their habitat had been poisoned.

At this point in the conversation, I can take no more. It’s barely light out, and in the morning I am especially vulnerable to despair.  I pull photos of plants on my phone for Ron and Matt to identify. It’s not that I don’t want to hear it; I just need my doses of toxic knowledge at non-lethal levels.

***

Ron Determann: Conservationist & horticulturalist extraordinaire.

Today we will not be visiting a roadside refugia, but climbing into Tallulah Gorge, one of Georgia’s most beautiful places, to look for the monkeyface orchid (Platanthera integrilabia) and some of its friends.  We hope to collect seed to bring back and grow in the tissue culture lab.  We’ll keep some seed and plants for back up and outplant seedlings to augment the natural population.  Growing things is Ron’s especial gift.  He has brought rare and endangered plants into cultivation that no one else has been able to grow.  The tissue culture lab that Matt runs at ABG is named after Ron.  

The tram making its very slow yet precipitous journey.

The orchids were sighted growing near the floor of the Tallulah gorge, nearly 1,000 feet down, alongside the Tallulah River.  The river is no longer the roaring terror that earned it the name “ the Niagara of the South.”  Dammed in 1913, the Tallulah River’s six falls have been quieted.

Nevertheless, we still have to find a safe place to cross the river to reach the orchids.  Brian Estes of Georgia Power knows just the spot and he's arranged a special treat for us.

Almost there. See the folks at the bottom?

We are taking the a tram that runs strait down the face of the gorge to the hydroelectric station below.  Hiking down would be pleasant, but that would take three hours round trip, leaving less time to hunt orchids.   

Climbing into the tram we are initially cautious of the open doors but are soon hanging out the sides taking photographs of the odd combination of flora growing on the slope:  natives, exotic invasives, and wetland plants taking advantage of the water flowing from tiny leaks in the penstock pipes that take water down into the hydroelectric turbines. 

Forging the Tallulah River

Our ride over, we leave the tram and put in earplugs so that we can walk through the noisy power station and begin our final descent into the gorge.  Soon we are scrambling over rocks and through trees and shrubs looking for a shallow place to cross the river.  Brian finds the spot and one-at-a-time we make our way through the water and over the rocks slick with moss. 

We are on the other side less than three minutes before Matt finds orchids.  We collect seed capsules and move to another spot.  The growth of shrubs is dense and the footing is uncertain, and everyone manages to grab hold of poison sumac at one time or another.  Having inadvertently nuzzled the stuff, I have a vision of my face 3 days from now erupting into painful blisters.  

Poison sumac in its autumn colors.

I next see my companions gathered at a seep where water has collected into what looks like a shallow pool but Brian has warned us is actually waist-deep silt.  Matt and Ron collect more seed.  I see Parnassia asarfolia in bloom, which I saw for the first time last week while collecting Isotria with Matt.  We thought we’d have time to stop and take photos on the way out, but no such luck.   

Parnassia asarfolia

While I am carefully photographing the exquisite blossom, the rest of the group continues the ascent.  The next thing I know I am alone.  I start to climb and call, climb and call.  At last I hear an answering voice.  By the time I catch up, I’ve lost my lens cap and some of my composure.  My hair is full of twigs and leaves. 

Everyone is standing around what may be the same seep only much higher up.  Sphagnum moss grows thickly at the edges of the wet rock face, and on the face itself are tiny round-leaf sundews, Drosera rotundifolia.  The red hairs on their leaves glisten with mucilage, a sweet but also sticky substance that lures insects to their doom.   

Sundews appear to be growing in light film on rock face.

Once stuck, the hairs bend inward and the leaf begins to fold over the insect. Meanwhile glands on the hairs secrete enzymes to dissolve and digest the insect.  Several days later, the meal complete, the leaf will unfold, ready to ensnare its next victim.  Carnivorous plants live in nutrient-poor conditions like this seep, catching and eating insects to supplement their diet.

The Drosera rotundifolia growing so abundantly in this seep is the same species of sundew that Charles Darwin prodded with everything but the kitchen sink.  To see what would make the sundew move, Darwin placed in its hairs—he called them tentacles—meat, dead flies, bits of paper, wood, dried moss, sponge, cinders, chalk, wadded strands of hair, and shards of glass.  What he found was that when repeatedly touched by minute objects, the tentacles would invariably enfold the object.  Meat, egg, and, of course, insects the plants retained and flooded with digestive enzymes until consumed. Innutritious material like glass and cinders the leaf released.

(Drosera rotundifolia)

Leaf (enlarged), tentacles on one side inflected over a bit of meat placed on the disc.
 From Charles Darwin's Insectivorous Plants (1875).  Drawing by his son George.

In Darwin's experiments not every touch resulted in movement.  Drops of water and other heavy pressures did not cause the tentacles to bend. Darwin concluded that thanks to this selective sensitivity “the plant is thus saved from much useless movement, as during a high wind the glands can hardly escape being occasionally brushed by the leaves of surrounding plants.”[iii]

Matt pointing to a sundew and not sliding down the cliff.

I did not stop to poke the sundews.  Nor did I look to see what prey they grasped in their hairs.  I concentrated on staying more or less upright.  Ron, however, did slip a few specimens into a bag.

In total we collect seed from five orchid species:

Platanthera integrilabia     Monkeyface orchid

Platanthera clavellata        Small green wood orchid

Pogonia ophioglossoides    Snakemouth orchid

Calopogon tuberosus         Common grass-pink

Malaxis uniflora                 Green adder’s-mouth orchid

Snakemouth orchid, Pogonia ophioglossoides

The snakemouth orchid (Pogonia ophioglossoides ) and the common grass-pink (Calopogon tuberosus) were especially exciting to find growing in Tallulah Gorge.  Both orchids are common in Georgia’s coastal plains, but this is the only known mountain population of each species.   

The seed can be grown into plants, and then the plants can be placed in mountain bogs that the Atlanta Botanical Garden is restoring.  The ideal is to grow material from the recovery location and return the plants to the original site to augment the natural population.  In the absence of such material, you can at least strive for a kind of genetic authenticity by using plants from the same kinds of locations, in this case mountain locations. As Ron says, “We don’t like to put Okefenokee orchids in mountain bogs, even if they are the same species.” 

“I could stay here all day,” Matt enthused.  No doubt he could, but it was time to start heading out.  

Ron with our guide, Brian Estes of Georgia Power

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[i] Chafin, Linda G. Field Guide to the Rare Plants of Georgia. Athens: University of Georgia Press, 2007.  p. 446.

[ii] Chafin, Field Guide p. 434.

[iii] Darwin, Charles R. 1875. Insectivorous Plants. London: John Murray. p. 264  http://darwin-online.org.uk/content/frameset?itemID=F1217&viewtype=text&pageseq=1