The ebony spleenwort (Asplenium platyneuron) is a fern with a strange name and a preference for growing where few other plants will. In New York City’s five boroughs, it is most frequently found squeezing its roots into the mortar of abandoned forts, railroad trestles, bridges and the foundations of old buildings.
Portraits of local flora and fauna.
Though this adaptation may seem odd, it is only natural for a plant that prefers alkaline soils. The decomposing mortar contains calcium, and is the closest thing to the fern’s natural habitat of rocky ridges and limey, dry soils. Like the famous Ailanthus trees that grow in Brooklyn, spleenwort grows best before much soil develops between the cracks in a wall. This inhibits competition and keeps the fern in full sun.
For those of us who associate ferns with the banks of cool, shady brooks lined by thick, loamy soil, the graceful little spleenwort comes as a surprise, growing on a hot, dry wall where finding a cactus might seem more likely.
Spleenwort is uniquely suited to colonizing these sites. Like all ferns, it does not flower but reproduces by means of spores, which form on the backs of its leaflets (or pinnae). The spores are dustlike and can easily be carried aloft by gusts of wind to begin new colonies, sometimes miles away.
The fern also reproduces vegetatively, growing small plantlets at the base of the mother plant. The spleenwort requires no insect pollinators, an effective if primitive reproductive technique.
Spleenwort might also be your neighbor. I have come to expect it in places like the old train trestle at Myrtle and Central Avenues in Glendale, Queens. It festoons some of the city’s oldest forts on Staten Island, busy bridge abutments in Manhattan and buried historic home foundations in the Bronx. It sprouts enthusiastically from between concrete slabs.
Ebony spleenwort is a small fern and grows two types of fronds. The “sterile” fronds do not produce spores and grow flush with the ferns’ chosen site. These fronds radiate from a central crown along with far longer “fertile” fronds that arch gracefully upward in the summer, sometimes reaching 10 to 12 inches in length. At the center of each frond is a shiny, dark brown stem (or rachis), which lends the “ebony” to the ebony spleenwort’s name.
Examining the undersides of these longer fronds, you’ll find dark brown, fuzzy dots called sori, which contain sporangia, the reproductive organs of the plant. These dots account for the other half of ebony spleenwort’s unusual common name, as early herbalists thought its shape resembled the human spleen.
Seeing the shape of a human organ in any plant was a key feature of the doctrine of signatures, a theory popularized by medieval herbalists that held a plant’s use could be divined by careful study of the shape of its leaves or roots, or of the conditions in which it grew (spleenwort leaves were used to purify the blood).
This belief accounts for many of our most colorful plant names. Some, like “liverwort,” “bloodroot,” “rattlesnake plantain” or even “nipplewort,” leave little to the imagination.