Cup Plant



Boneset, Cup Plant, Coreopsis

Silphium perfoliatum shares the same species names as Boneset and has the same perforated leaf structure.  The difference is one of scale.  Cup Plant, the large green plant in the center, has leaves that are much broader and join the stem to form a cup that collects rain water.  Apparently, birds use these small basins for drinking water.  The scale carries over to the entire plant, which can reach from four to ten feet tall.  They are topped with clusters of medium sized yellow sunflower-like blooms.  The plant has a large taproot as well as shallow rhizomes that give rise to colonies.  Like most composites, the flowers of the Cup Plant attract many pollinators, and the seeds are favored by goldfinches and other seed eating birds.  The plant in the picture was a seedling last spring that I carried over the winter in a pot awaiting its permanent home.  When I planted it here this spring it was only about 6 inches tall and wide.  As you can see, it has grown quickly this year and should send up flowering stalks next year.  Cup Plant, as a member of the genus Silphium, has some impressive cousins.  Prairie Dock, S. terebinthinaceum has the same tap root and clusters of yellow flowers, but the foliage is unique. Rather than bearing leaves on the stems it has a cluster of huge paddle shaped basal leaves out of which rise bare stalks topped with flowers.  This arrangement makes Prairie Dock a see-through plant.  The leaves, while large, are not much taller than a garden mum.  Planted at the front of a bed, the large leaves provide great impact, while the flowers seem to flutter on stems above head height.  S. laciniatum has a similar arrangement, but the leaves are even more handsome, cut like huge chicory leaves and held at a North/South orientation to minimize the exposure to hot sun.  Rosin Weed, S. integrifolium is intermediate in form, with lance shaped leaves born on the stems and clusters of flowers on branched stems.  This genus was an important component of the prairies and once tickled the sides of bison and elk.  Now they provide dramatic accents to native landscapes.