Two native species of plants belonging to the Silphium genus are found in Minnesota. The second part of the cup plant's scientific name, "perfoliatum," refers to its perfoliate leaves, with the leaf blade surrounding the stem so the stem appears to pass through the leaf. Opposing pairs of these perfoliate and upward-pointing leaves form a "cup" that can hold water for many days after a rainfall.
The cup plant is tall, reaching heights of 8 feet or more. The opposing leaves are very large and can measure 6 inches wide by 10 inches long on mature plants. These giant leaves are coarsely toothed around the edges and feel rough like sandpaper to the touch. Stems are straight, smooth, and square-shaped, often with a reddish appearance. Each plant may produce between 10 and 30 yellow flowers, situated at the top. These 2- to 3-inch flowers resembling small sunflowers bloom from July to early September. Flowers have an average of 20 to 30 petals.
The cup plant is a common and widespread native across much of the central United States from Minnesota to Texas as well as many eastern states. Here in Minnesota it is common to find cup plants in the southern half of the state, and less so as you move northward. Though it is not a true prairie specialist, this plant is more likely to be found in the general vicinity of prairies—specifically on the edges of prairies, where nearby woods provide some shade during the day.
Benefits to Wildlife.
The cup plant is uniquely suited to benefit wildlife. Birds and insects, which are keenly aware of its ability to catch and hold water, drink from the plant. I have seen bees and wasps land on the leaves and immediately head toward the center where water might be found. Last season I watched an adult red-winged blackbird dip a bill full of insects into the cup, possibly to moisten or freshen them, before feeding them to its offspring. Birds readily take to the tall and sturdy plants to proclaim territory, sing to attract a mate, or seek shade from the hot summer sun under its large leaves. In July and August, the cup plant's flowers are a magnet for butterflies including monarch, eastern tiger swallowtail, red admiral, and painted lady. The insects you're most likely to find on this plant are red aphids, which can be found in vast numbers, especially on the undersides of the leaves. These aphids provide a plentiful food source to smaller birds such as common yellowthroats, yellow warblers, and hummingbirds. Flowers gone to seed are seemingly irresistible to American goldfinches, which show up in droves in late summer in search of the tasty seeds.
Travis Bonovsky,, freelance writer