Guide to Growing Cup Plant (Silphium Perfoliatum)

A few years ago, I planted Silphium perfoliatum, also called cup plant, in a wet spot in my back yard garden. The plant has thrived there, now growing to be about 7 to 10 feet tall in the summer. As you are considering your winter plant orders, you may want to make space for this dramatic and easy-to-grow perennial.

According to Illinois Wildflowers, cup plant (Silphium perfoliatum) is a 4' (1.25 m) to 10' (3 m) tall perennial that remains unbranched except near the top of its flowering stems. The central stem of cup plant is thick, hairless and has four sides. Cup plant leaves are large, about 8 inches long and 5 inches across, and meet the stem in opposite pairs. Cup plant (Silphium perfoliatum) gets its name from the way the broad leaves join around the stem to form a cup that holds water after a rain storm. Leaves are rough, with a sandpaper-like texture and have serrated edges.

In mid-summer, cup plant (Silphium perfoliatum) bears clusters of yellow flowers. Blooms on my cup plant are typically the tallest part of the plant, reaching about 7 feet to 10 feet in height. Each flower is about 3 inches across and is shaped like a daisy. Each flower cluster may have a dozen or more blooms. I find that the flowers attract many insects and that they make good cut flowers.

Cup plant (Silphium perfoliatum) does best in full sun or part shade, in rich soil. My cup plant is planted in light shade, in the wettest spot in my yard. Silphium perfoliatum can topple over in strong winds, and it may lose leaves during a drought. Cup plant will survive droughts, because it, like many native plants, has a deep and extensive root system. It does, however, like moisture. If you're considering cup plant for a home garden, be warned: it spreads by rhizomes. Thus it's a good idea to put cup plant where you don't mind if it spreads.

Cup plant (Silphium perfoliatum) is found throughout Illinois and is fairly common throughout the midwestern United States. It is a native of tallgrass prairie. Cup plant will thrive in hot weather, when many other garden plants have wilted. Cup plant is a member of the aster family.

Researchers at South Dakota State University have investigated whether cup plant may be grown as a source of biomass on land not suited for agricultural uses. The researchers don't expect that cup plant would be grown in monoculture, but would be mixed with other plants.

Cup plant is sold by specialty vendors such as Prairie Nursery and Prairie Moon Nursery. I ordered mine as a bare-root plant. Unless you plan to cover a very large area with native plants, there's no reason to bother with seeds. For most home gardeners, one bare-root plant will be enough.