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Each year, a team of Columbia parks workers, state and federal agency experts, and river enthusiasts venture out on the waterways bordering the Three Rivers Greenway to conduct an important scientific survey. They paddle kayaks to locations on the Broad, Saluda and Congaree rivers where rocky shoals spider lilies anchor their roots.

The rocky shoals spider lily (RSSL) is listed as a federal species of concern, an acknowledgement that the plants, and especially their required habitat, are rare and threatened. RSSL (scientific name Hymenocalis coronaria) are native to South Carolina, Georgia and Alabama, and as their name suggests grow only in the rocky shoals of flowing waterways. They have been identified in about 50 locations worldwide, usually along the fall line where rivers move from rocky terrain to flatter coastal regions.                                                                                                                                                                 

Their root system clamps along and around rocks, producing an almost muscular hold that can withstand rapidly flowing water. From that tough base arise deep green stalks topped by delicate-looking white flowers during the blooming season of late spring and early summer.

If you’re a regular on the greenway trails, you’ve no doubt seen the educational signs about RSSL. From a few vantage points on the walkways, you can spot the blooms bobbing above the shoals. (Some can be seen from the I-126 bridge, but please only look for them as a vehicle passenger.)

Because of their rarity, they get special attention — thus the research effort along the greenway. The Federal Energy Regulatory Commission (FERC), which periodically approves the licensing of hydroelectric facilities, included a RSSL Enhancement and Monitoring Plan in the most recent relicensing of the Columbia Hydroelectric Project. That’s the small power plant, currently not operating, next to EdVenture at what used to be the end of the Columbia Canal.

The surveyors aim to count the numbers of plants at each of a half-dozen main populations each year to gauge the health of the population. It’s much easier work when the rivers are at low levels, but heavy rain and subsequent flooding associated with tropical storms the past few years have made the surveys challenging. More frequent high water flows since the historic 2015 floods breached the canal embankment and forced closure of the power plant also have challenged the rugged RSSL.

The 2020 survey report notes that strong flows have scoured almost all vegetation in one of the previously vegetated islands just below the diversion dam. Also, the upstream end of one of the largest patches of plants at the confluence of the Broad and Saluda rivers has suffered some loss. But new stalks have popped up on the downstream side of that area, which the survey refers to as Lily Island. In general, the RSSL population remains healthy if slightly depleted from a decade ago.

And while a continuation of more frequent and historically high flooding (can you say climate change) could impact the RSSL population, the survey report notes the most pressing danger is from people. Too often folks recreating along the river see the beautiful blooms and decide to pick them or pull up their roots to try to relocate the plants to backyard gardens. Thus, education is the other major goal of the survey team.

To that end, in addition to educational signs along the greenways, the City of Columbia parks staff has conducted training sessions for local outfitters who guide paddling tours of the river, created laminated cards with talking points about RSSL for those guides, and designed posters for outdoor gear shops. The message, which applies also to those who take to the waterways in their own boats, is to admire the delicate flowers from the river banks or the water and avoid tromping through the shoals where they grow.

The survey team also notes that two similar native species — the Carolina spider lily (H. occidentalis) and the coastal spider lily (H. crassifolia) — have a similar appearance to RSSL and thrive in local gardens. Plant lovers should check for those at nurseries and leave the more rare RSSL along the greenway alone.

One final note: As beautiful as the RSSL are along the Three Rivers Greenway, if you want the peak RSSL experience in South Carolina, head up I-77 to Landsford Canal State Park from mid-May through mid-June. The larger RSSL population there stretches from one side of the wide Catawba River to the other in several spots. You can take them in from a riverside trail, but if you have access to a kayak or canoe, paddle out among the blooms. It’s one of those life experiences you’ll never forget.