Cup Plant is tall erect perennial plant, growing 4 to 8 feet high, on stems that are stout, square in cross-section and smooth (but can be somewhat rough or have fine short hair) and unbranched below the inflorescence.
Leaves: The upper stem leaves are opposite and are joined at the base and thus form a "cup" around the stem. Leaves are rough to the touch, longer than wide with a few large coarse teeth. They taper to a long pointed tip. Lower basal leaves have a delta shape which tapers at the base to a stalk.
The inflorescence is a long-branched panicle atop the stem that contains numerous stalked flower heads. It rises from the upper leaf axil.
Flowers: The flower heads are 2 to 3 inches wide when open, with 16 to 35 yellow ray flowers, which are fertile; these surround a central disc that is 1/2 to 1 inch wide, composed of functionally staminate florets (not fertile) that have yellow tubular corollas which protrude outward from the disc plane. The flower head has several series of floral bracts (phyllaries) that are green with very fine hair. The outer series is ovate in shape with triangular pointed tips which reflex when the flower opens. In the Silphiums, each ray flower is subtended by a phyllary. Flower stalks can have fine short hair or some surface roughness.
Seed: Pollinated flowers produce a dry thin flattened dark brown achene that is without fully pappus, but winged and light enough to see some distribution by wind.
Varieties: There are two recognized varieties: var. connatum, which is restricted to four states on the east coast and var. perfoliatum, which is native most of the eastern half of the continent as explained below. Differences concern the amount of roughness and hair on the stems and flower stalks. Minnesota authorities list var. perfoliatum as the native plant.
Habitat: Cup Plant has an extensive root system with a tap root and near surface rhizomes and does not transplant well except when very young. It grows best in full sun with wet to moderate moisture.
Names: The genus name, Silphium, is from the Greek word silphion, which was a plant of North Africa said to have resinous juice that was medicinally sought after. This plant appeared on ancient Greek coins of the city of Cyrene. Silphium is used today for a group of plants with resinous juice. The species, perfoliatum, means 'with the leaf surrounding or embracing the stem'. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: This is one of four Silphiums in the Garden. For more detail on this plant and the other Silphiums at Eloise Butler see our article "The Four Silphiums".
Above: Cup Plant flowers form at the top of the stem in the tall branched panicle rising from the upper leaf axil.
Below: The unique leaf structure. Note the coarse teeth.
Below: 1st photo - The stem of Cup Plant is square, unlike our other three Silphiums, and mostly smooth. 2nd photo - The outer green phyllaries of the flower head have triangular tips and fold backward when the flower opens.
Below: Seed heads. The outer rows, formed from the ray florets are the actual seeds. The seeds are flattened with wings and no attached pappus.
Below: 1st photo - The Flower head with bee and beetle. 2nd photo - A stand on tall Cup Plants on August 1st.
Notes: Eloise Butler introduced this plant to the Garden with specimens collected at Minnehaha (Minneapolis) in Sept. 1907; in August 1908 with a plant from Glenwood Springs, (near the Garden); and again in 1911 from plants obtained within Glenwood Park (which surrounded the Garden). This plant was listed on Martha Crone's 1951 inventory of plants in the Garden at that time and on the later Garden census lists. It is native to Minnesota in most counties across the southern part of the state south of the Minnesota River, the SE and north as far as the metro area but generally absent westward of the metro counties. In North America it is found from the Central Plains eastward in the U.S. except TX, FL, SC and NH. In Canada it is known in Ontario and Quebec. Cup Plant is one of two Silphiums native to Minnesota, the other is Compass Plant, S. laciniatum.
It can become weedy and invasive in certain areas. Connecticut has banned the plant but it is not controlled in Minnesota. Cup Plant is the only Silphium that is mentioned in literature for medicinal usage. As the root contains a gum and resin, the root has been medicinally used as a tonic, diaphoretic (stimulates perspiration) and diuretic. Densmore (Ref. #5) listed usage by the Chippewa for lung ailments, hemorrhage and joint pain. Others that briefly list use and dosage are Grieve (Ref. #7) and Hutchins (Ref. #12).
Eloise Butler wrote of this plant: "Another composite adorned with yellow ray petals and towering in splendor above its competitors in rich, alluvial soil, is the Cup Plant. The large leaves, arranged in pairs along the stem, are united at the base to form a deep cup for holding water. This may serve the double purpose of tiding the plant over a dry spell and of keeping unwelcome, crawling insects from the flowers. People in the tropics use a similar means to keep the ants from food by inserting the legs of the dining tables in dishes of water." Published in the Minneapolis Sunday Tribune, July 16, 1911
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"