Native to tall grass prairies in the western and southwestern United States, the cup plant, Silphium perfoliatum, or cupleaf rosinweed, is a plant out of place in this region. Introduced as an herbaceous ornamental, it escaped the garden and is quickly becoming a species of concern, invading river corridors throughout the Ausable River watershed.
Historically called the Indian cup plant, Native Americans used the hardened resin for chewing gum and an extract from the root to stop chest and back pain and prevent hemorrhaging in the lungs.
A positive indicator of healthy prairie habitat in the Midwest, this 7-to-9-foot-tall, non-native giant easily crowds out other native plants in the Adirondacks, often creating dense, expansive monocultural stands. Its large seeds are spread by waterways, birds and curious gardeners.
Cup plant flower
Steven Flint, terrestrial invasive species project coordinator of the Adirondack Park Invasive Plant Program, traced the cup plant's introduction back 37 years to a camp in Keene. Innocently planted as a striking ornamental, approximately 60 feet from the ever-dynamic East Branch of the Ausable River, its seeds were eventually carried downstream. Infestations now extend to Keeseville.
The cup plant has a thick, smooth, square stalk with yellow daisy-like flowers 4 to 6 inches in diameter. Flowers bloom mid-July through early August in the plant's second and third year of growth. With large, jagged, ovate leaves that fuse together surrounding the stem, plants collect water at the center of the "cup," attracting many insects and frogs.
Able to sprout from seed, plugs or pieces of the plant, the cup plant can spread rapidly along river banks and roadsides, and dominate gardens as well. It will grow anywhere with wet to average soil moisture and full to medium light.
Since the cup plant is native to parts of the United States, its planting as a "native plant" in the Northeast has been encouraged. And, due to its size, it is occasionally marketed as a "living fence." However, unlike in the Midwest, in the Northeast cup plant exhibits an invasive tendency and its propagation should be discouraged.
To prevent this aggressive perennial from spreading further, select alternatives to the cup plant for your garden. If plants are already established, landowners should not allow young infestations to go to seed, the primary means of reproduction. Dig out plants at its earliest emergence in late spring. Older plants grow deep, massive, root systems, which makes removal more difficult. Securely bag the roots and stalks and place bags in a sunny area to decompose, then dispose of as refuse.
Although a pretty plant, cup plant should never be transplanted from the roadsides where it has invaded to garden settings, which has already accelerated its spread in the region. Also, if you are getting top soil delivered to your house, know its source to reduce the risk of receiving "dirty dirt," soils infected with invasive seeds and rhizomes - another way that unsuspecting landowners end up with invasive plants.
Cup plant can be confused with Helianthus species (sunflowers), which have flowers that look similar but they do not have the cup-forming leaf bases that the cup plant does. To report cup plant sightings or if you have questions about control techniques, call Steven Flint at the Adirondack Chapter of The Nature Conservancy, 518-576-2082.
Amy Ignatuk is a summer intern with the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy. A resident of Upper Jay, Amy is a student at Roger Williams University in Rhode Island. 'Eye on Invasives' is a biweekly column that spotlights a top invader when it is easiest to identify.