as the last of fall’s leaves turn from red to brown, one final color is painting new york’s scenery: the fiery yellow-encased red berries of the asiatic bittersweet. which is kind of an appropriate name if you weigh their beauty against their destructive potential.
a bunch of the greenspaces in the outer boroughs have a distinct “vineland” look, where low bushes and dying trees are blanketed by a tangle of leafy vines. a few aggressive introduced species are responsible for this look, mostly porcelainberry, japanese honeysuckle, and asiatic bittersweet. these plants out-compete the other flora by constricting them and stealing their access to the sun, utterly transforming the surrounding area in the process. off the top of my head, breezy point, floyd bennett field, kissena park, alley pond park, pelham bay park, and canarsie park all have areas that look like they’ve lost to the vines, like this:
asiatic bittersweet was the main plant i noticed while i was out this weekend, so i figured i’d take an afternoon to learn more about its ability to transform so many of new york city’s parks.
asiatic bittersweet first appeared in the united states in the 19th century, imported from east asia as an ornamental plant. one article i found traced its origin in the united states to a catalogue from flushing, queens’ kissena nurseries in the 1880s. this is notable to me because the nearby kissena park is one i associate with the vineland look, and its tangled captors may be related to some of the first asiatic bittersweet plants that showed up in the united states. it subsequently became a popular ornamental plant for rich people, then a widely planted vine in gardens and along highways, then a pest which out-competed its cousin, the american bittersweet.
the plant’s success comes from its multitude of bright fruits which are poisonous to humans but attract hungry birds who disperse its seeds, its ability to grow in a variety of light and soil conditions, and most importantly, its habit of forming twisted braids which let it climb all over the competition. plus it hybridizes asymmetrically with american bitterweet: when the two come in contact, the american bittersweet produces hybrids but the asiatic bittersweet usually doesn’t. people have realized that you shouldn’t be allowed to buy or grow such a plant—new york bans the knowing sale or transport of it. but it continues to show up in nurseries mislabeled as the less aggressive american bittersweet. and it continuous to transform our landscape, potentially permanently.
this vine does far more than just dominate the competition; it prevents the competition from ever competing again. in 1951, the connecticut college arboretum acquired a tract of agricultural land the size of a small park and began regularly surveying its plant life as its species makeup evolved over time, what we call ecological succession. for the first twenty years, the entire grassy field started to grow native woody plants like bayberry, sumac, blackberry, and black cherry. but in the early 1970s, slightly outside the study area on the southwest corner of the field, a new plant began to take hold: asiatic bittersweet.
by the 1983 survey, the bittersweet had taken over the western half of the study area, leading to two very different looking plant communities. the eastern half had grown into a young forest of mostly black cherry trees (and other plants) while the western half’s plants had been constricted by vines. ten years later, the western half had that hallmark neglected park look where many of the surviving trees and shrubs were now completely engulfed by the bittersweet, and some were beginning to die. the eastern half had matured into a hardwood forest with black cherries, red maples, tupelos, oaks, and more, with layers of other shrubs.
the study authors jean fike and william niering weren’t optimistic about the future of the eastern half. bittersweet from the western half was already encroaching by the time they published their their 1999 paper: “like a carpet being unrolled, it appears to have the potential of possibly engulfing the entire early forest community that developed simultaneously with it…” they wrote.
it’s not just the plant’s aggressive nature that makes it worrisome. in a 2009 paper, university of connecticut researchers stacey leight-young, hillary o’donnell, andrew latimer, and john silander, jr. compared the soil between seven pairs of plots, where one plot had asiatic bittersweet and one did not. the soil from the plots with bittersweet was more acidic, had higher levels of potassium/calcium/magnesium, and natural chemical processes like decomposition and nitrogen mineralization (the process that converts nitrogen into the inorganic form usable by plants) was happening faster.
that has important implications for conservation: plants that once thrived in the region might not take as well to soil previously inhabited by asiatic bittersweet.
i noticed an interesting parallel between the studies and new york city, one that explains why so many of the city’s parks look the way they do today. like i told you in the bluebird article, new york city’s outer boroughs once had lots of farm fields which were abandoned in the middle of the 20th century. according to one of my favorite nyc parks department documents, plowing stripped the soil of the seeds that native vegetation would have left behind, and the surrounding populated areas had many exotic species whose seeds the wind and birds could easily introduce to these fallow fields. so, rather than grow into the expected hardwood forest or maritime plant communities, many parks built on this land turned into vinelands or other exotic-dominated ecosystems.
them’s sorta the breaks: people bring plants to new places, and those plants make those places look different. new york has a lot of people, who have brought a lot of plants, and that’s given the city a totally new look. the city can undo some of the effects with intensive management, which looks like a game of whack-a-plant requiring they tackle the vines, then kill the mugwort and phrags that replace the vines, then the autumn olive and multiflora rose, etc. so, idk, go vote or write a letter or send an angry tweet or volunteer or something. if you have any other good ideas for how to get the parks department to actually take care of the parks (and in a way that doesn’t like, forcibly displace homeless people) i encourage you to tell me and i can broadcast them in the next newsletter.
postscript
sorry for the depressing post. i was birding at breezy point and there was bittersweet everywhere and i thought “wow that’s so pretty, i should blog about it” knowing full well that i’d just get sad. i was originally gonna blog about a cool bird i found last week, i’ll probably still do that, but not this week because i thought the newsletter was getting too birdy.
speaking of birds, new york’s best season, seagull season, is beginning! there have been thousands of gulls in the new york harbor the past few days, some pushed around by a few days of weird weather, others migrants arriving for the winter or passing through on the way south. just this weekend i’ve seen six species of gull: ring-billed, great black-backed, lesser black-backed, herring, laughing, and bonaparte’s. there at least two other species present in the city which i didn’t see, black-headed and iceland.
but the gull i really want to see in new york city is the franklin’s gull, a bird i’ve seen in north dakota which breeds in the great plains and follows farm equipment around like fishing boats before migrating to the west coast of south america. they’re rare in new york state, but sometimes they’ll show up after sustained stormy weather with strong west winds pushes migrating birds eastward. look how cute!