Tuesday, October 1, 2013

Surrounded, but No Surrender!

Porcelain-berry, the "kudzu of the North," on the periphery of the Pennypack Preserve
For some reason (perfect temperatures, soil moisture, carbon dioxide concentrations, or a synergistic interaction of all three), the invasive Asian vine porcelain-berry (Ampelopsis brevipedunculata) "exploded" in the Pennypack Preserve this summer.  The perennial vine is ever present, and always the biggest threat in the natural area.  When I began my job here 25 years ago, one of the first tasks I set for myself was to bring the plant under control in the most heavily infested areas, and I was really able to knock it back with several years' intensive mechanical and chemical control efforts.  But, as I said, this year it has re-surged with a vengeance. 
Porcelain-berry fruits in varying stages of ripeness
Porcelain-berry was introduced to the united States from eastern Asia, probably as a garden ornamental.  It's fruits are attractive for about two weeks in the fall, but the rest of the year the plant just looks like a sprawling grapevine - to which it is very closely related.

Once the plant escaped the bounds of gardens (undoubtedly aided by birds that eat its fruit and then defecate the seeds elsewhere), it found a perfect home in the Mid-Atlantic.  It grows up into the canopy, spreads out to capture sunlight, and blankets the trees supporting it, eventually shading the trees to death or ripping off their limbs when the weight of the vines becomes too much for the tree to bear, especially when covered in snow and ice in the winter.
Porcelain-berry flowers attracting a honeybee
Porcelain-berry is served by generalized pollinators, so it is not dependent on a specialized bee, wasp or bat to spread its pollen.  And, while it's an introduced species, our native North American songbirds (and white-tailed deer) consume it readily, helping to spread the plant across the landscape, probably because it is so closely related to the grapes that are already familiar to our native species.

The only insects I have ever observed damaging porcelain-berry leaves are invasive, non-native Japanese beetles, but they never become numerous enough to inflict real harm to the plant.  I suspect that even if the plant has a specific disease or insect pest that keeps it in check in its East Asian homeland, such a disease or insect could never be imported into the United States as a biocontrol agent because it likely would also attack commercial grapes.
A porcelain-berry rhizome
Porcelain-berry develops an extensive, thick underground stem or rhizome.  The rhizome grows through the soil and sends up shoots ever few feet or so.  An infestation of porcelain-berry may actually consist of only a few plants all growing from the same underground stems.  Cutting off a few of the above-ground vines hardly fazes the plant, which has plenty of resources stored underground.  The only feasible method of control is to poison the plant with a broad-leaf herbicide applied either to the foliage or directly onto the rhizome after an above-ground stem is severed.
One of Pennypack's board members asked me to do a photographic inventory of land parcels on the periphery of the preserve that we might be able to acquire to add to the natural area.  I completed the inventory and prepared a PowerPoint program that I presented at the last board meeting.  In my remarks prefacing the presentation, I alerted the board members to note that every single one of the parcels I had photographed that was not maintained as a meadow or as lawn was completely overwhelmed by porcelain-berry.  Even if we got the plant under control within the preserve, the Vandals are at the gates on private properties we can't touch.

But we do have a chance to maintain the natural diversity inside the preserve, and we will redouble our efforts to try to bring porcelain-berry under control or the winter and during the next growing season.

Submitted by
David Robertson, Executive Director

No comments:

Post a Comment