Rocky Shoals Spider Lily adds rare beauty to Southern riversides | Mystery Plant

I’ve come up with a rather romantic imaginary Southern scene.

Picture this: it’s an early evening in late spring, one of those days that started off cool, but heated up quickly by midday, and suggesting things to come. We’re looking out over an expansive valley of one of our rocky rivers, and what lies before us is an extensive boulder-field, or shoal.

Granite rocks, some the size of a school bus, are strewn randomly across the entire river’s shallows, with a complicated system of whirlpools and rapids. Despite the lingering afternoon heat, distinctive thrills of chilly air rise up from the rapids.

Across the horizon a flicker of lightning, followed by a desultory low growl. The last chittering swifts fly close to the water, and the first bats appear, winging their way erratically while catching dinner. Although no stars are visible, and only Venus is borne over the flood, look below: an entire constellation of starry flowers appears amongst the rocks, wafting their sweet perfume and attracting quiet moths.

Is this too imaginary? No. In fact, our Mystery Plant — Rocky Shoals Spider Lily, Hymenocallis coronaria — speaks to such a fantastic natural display, still visible in a few places in the South.

This is a rare plant, one related to cultivated amaryllis and jonquils, and native only to a relatively narrow band in South Carolina, Georgia, and Alabama. (It ought to be in North Carolina. But where?) This species is specialized to live in rocky river shoals. It’s a bulb-former, its bulbs wedged within the cracks of the rocks.

Now, they must obviously be tightly wedged, when you consider the force of the various floods coming down the river at times. Generally, plants that are not specialized for these “high energy” environments, such as recently sprouted weeds, are easily swept away.

Our Mystery Plant produces long, sword shaped leaves, up to 3’ long, and then a thick stalk, topped with a cluster of white flowers, each bearing three spidery sepals and petals, and a prominent, and very impressive, white cup, featuring six spidery stamens.

The pistil within has a long style, suitable for receiving pollen from visiting sphinx moths, sipping the sweet nectar. Each flower of the cluster opens one at a time, lasting but a single beautiful evening.

Following flowering, green capsules ripen, then release their plump seeds. The seeds tend to sink into the current, lodging themselves in cracks, where they will germinate and form new plants. Such a magnificent part of our natural landscape.

Regrettably, manipulation of the rivers, especially by the formation of lakes and controlling flow out of the dams, has destroyed most of the populations of this exquisite wetland species.

Large, healthy populations still exist in South Carolina’s Catawba River (at Landsford Canal State Park) and in Alabama’s Cahaba River (Cahaba River National Wildlife Refuge), and visitors to these sites can observe the lilies, along with plenty of other wildlife species.

John Nelson is the retired curator of the A. C. Moore Herbarium at the University of South Carolina. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or email johnbnelson@sc.rr.com.

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