Blunt Cliff Fern in Harlem


Blunt cliff fern (Woodsia obtusa) festooning the Metro North train trestle in Manhattan. This fern is native and uncommon in NYC.
The ferns are back! Blunt cliff fern (Woodsia obtusa) is growing quickly and by August should be nicely carpeting the sides of the Metro North train trestle that runs along Park Avenue in Spanish Harlem. This fern first came to my attention when I started my job 4 years ago. I walked under the trestle on my walk from the 103 Street 6 train to my office, all the while wondering what species they were but never stopping to look...until finally I did. Woodsia obtusa is not a common plant in NYC. Yet here they were, overwhelming the walls along Park Avenue.

Finally, the following year I did a floristic survey and found that within the mortar of this structure a unique plant community exists, including four fern species that are rare in the City.

Brief history - the trestle extends from 110 to 101 Streets. This portion is constructed of stone and was built in 1870. The mortar was created out of the rock, soil, timbers and various mining debris from creation of the rail tunnel under Park Avenue. Suitable fern habitat was created as these materials weathered and seeps were formed.


Close up of Woodsia obtusa

Surveys found 43 plant species. Whether native or exotic, the majority of the other plants present in the plots were weedy species more commonly found in marginal areas like vacant lots and roadsides. Five ferns were found, including sensitive fern (Onoclea sensibilis), a common wetland species, able to survive do to water pooling in the masonry. The other four are rare in NYC: ebony spleenwort (Asplenium platyneuron), walking fern (A. rhizophyllum), purple cliff-brake (Pellaea atropurpurea) and blunt cliff fern (Woodsia obtusa), are typical of cliff habitats. At approximately 30 feet tall, this trestle acts as a Manhattan cliff.

If one looks carefull around the perimeter wall of Central Park, you will find both blunt cliff fern and ebony spleenwort.