It is a strange-looking plant growing in a wetland beside the road — a three to four-foot stump that is maybe three-quarter inches in diameter all the way from its base to its tip, and completely covered with a dense layer of many small thorns. These stumps appear to be broken off, but on closer look the upper tip of each stump is one large terminal bud that may be damaged.
Then we notice that there are several other such short stout stumps nearby. And there is a larger tree, maybe 25 feet tall, with only a few long branches reaching for the sun through the other trees and shrubs. The thorns on these branches are greatly reduced in size but not in abundance.
Ecologist Wendy Culbert knew that she had seen this strange plant before, near Philadelphia. A quick glance through some field guides confirmed that the plant is called Hercules’ club, with a Latin name of Aralia spinosa. As with many plants, there is more than one common name for this plant. It is also known as devil’s walkingstick.
According to the Martha’s Vineyard Sandplains Restoration Project’s The Flora of Martha’s Vineyard, this species is not found on Martha’s Vineyard. Tom Clark, collections and grounds manager for the Polly Hill Arboretum, reports that they do not know of any other locations for this species on the Island. The Vascular Plants of Massachusetts: A County Checklist, produced by the state, shows it as present in eastern Massachusetts, with the closest known location in Bristol County, which includes the northern shore of Buzzard’s Bay. It is not known to occur in Plymouth, Barnstable, Dukes or Nantucket Counties.
How exciting! A new species for the Vineyard.
Field guides and botanical texts uniformly emphasize the stout trunks and twigs covered with numerous coarse prickles, which are certainly present on these plants. This species also has long, narrow leaf scars that almost completely circle the twig. Prominent features that we can not see at this time of the year include their large — up to one yard long and one yard wide — compound leaves, and small greenish-white flowers in July and August arranged in large, flat, branched terminal clusters (umbels) up to three feet long. These flower clusters then produce similarly large clusters of small, fleshy, purplish-black fruits that contain one seed.
Given the size of their leaves and flowers, it is no wonder that the buds are so big and prominent. The plant needs to have strong supports for such large leaves, flowers and seeds.
This species may have some value as a food plant, as the young leaves may be finely chopped, cooked and eaten, providing they are gathered before their prickles harden.
Their berries apparently have some medicinal value, as well, as early settlers may have used them to treat toothaches and rheumatic pain. That same report, however, cautions that consuming large amounts of the berries can be fatal. Another source cautions that these medicinal values may be from an unrelated species, prickly ash (Zanthoxylum clava-herculis), that is also called Hercules’ club.
Apparently it is a novelty plant used in landscaping due to its large handsome foliage, large showy clusters of flowers, and its “grotesque” (not my description) growth form. While this species is native as far north as Pennsylvania, this same author suggests that the more northern plants may be a very similar species from Asia (Aralia spinosa elata), which can more readily survive in our colder climate.
Tom Clark also points out that this species is clonal, spreading via underground rhizomes, and that its berries are eaten by birds, so that it could become invasive and spread rapidly into nearby disturbed areas. Now that we know this species is here, in the Seven Gates area, we should look for it elsewhere on the Vineyard and monitor its known location to see if it is spreading.
Robert Culbert leads guided birding tours and is an ecological consultant living in Vineyard Haven. Columnist Suzan Bellincampi returns next week.