On the western end of the park, there are pockets of exposed limestone surrounded by older Precambrian rock layers that were thrust over the younger Paleozoic formations 200 million years ago when the continents collided. Cades Cove and Wears Cove are two limestone “windows” and between them is a lesser known opening called Whiteoak Sink. There are no maintained trails into the sink, and park officials would probably prefer people stay out of this unique habitat. However, Whiteoak Sink is one of the worst kept secrets in GSMNP. A well-worn manway off Schoolhouse Gap leads to the floor of the sink and the waterfall that disappears underground amid the karst features of caves and sinkholes.
The trail descends through a typical Smokies forest – dying Hemlocks, Dog-hobble, Rosebay Rhododendron, Umbrella and Fraser’s Magnolias, Tulip Tree, Partridgeberry, Pipsissewa, Indian Cucumber Root, Hearts-a-bustin, and various Oaks. As you approach the sink floor, however, the forest character changes and the types, numbers, and sizes of plants indicate that this is no ordinary place.
The richness of the herbaceous layer is testament to the fertility of limestone-derived soils. Robust, tall plants thickly cover the ground. Even species that are often demur and retiring grow with exceptional vigor in Whiteoak Sink. Wild Ginger (Asarum canadense), for example, cascades down a small bluff and works its way among the other plants with foliage twice to three times normal size. Because of the higher pH soils, plant species uncommon in the Smokies grow in lush quantities. Guyandotte Beauty (Synandra hispidula), Wild Blue Phlox (Phlox divaricata), and Shooting Star (Dodecatheon meadia) wow visitors at the height of their flowering in spring.
A few years ago at the Spring Wildflower Pilgrimage, a pilgrim asked what the sweet and heavenly fragrance he noticed in Whiteoak Sink might be. It is the Phlox. Few plants are as delightfully fragrant and able to infuse their entire surroundings with perfume quite like Wild Blue Phlox. Resurrection Fern (Pleopeltis polypodioides var. michauxiana) is found in the sink, and the limestone loving Purple Cliffbrake (Pellaea atropurpurea) and Bulblet Fern (Cystopteris bulbifera) are growing near the Blow Hole, a narrow cave opening that continually pumps out air in the mid-50-degree range. The Blow Hole has been caged to protect curious humans and threatened bats alike, but hot and weary hikers can cool off quickly just standing next to it.
Other interesting finds include Hazelnut, Orange-fruited Horse Gentian, Huger’s Carrion-flower, Green Violet, and perhaps a distinct variety of Cutleaf Coneflower (Rudbeckia laciniata var. humilis). Dr. Pat Cox extensively studied the genus Rudbeckia and, on our Friday visit to the sink, discovers compelling evidence in support of this variety. We spot neat snails, grasshoppers, and a very weird fungus. Along Schoolhouse Gap Trail, we see a Northern Green Frog cooling off in Spence Branch, Dung Beetles grocery shopping for the family in fresh piles of horse manure, an Ebony Jewelwing Dragonfly, colorful Centipedes, and lots of Tiger Swallowtails.
On our way out of the sink, I am in the lead and stepping carefully on my swollen ankle when I spy a slender, 3-foot Copperhead stretched across the trail and blending frighteningly well with the color of the soil about 5 feet in front of me. A member of our party irritates him from a safe distance with a trekking pole and convinces him to move out of the way, but not before he strikes two or three times at the annoying pole. I’m rather grateful now for the hurt foot, for without it I might well have provided, completely unaware, an annoying provocation to strike by stepping on him!