Few grieved when the last buffalo left Wisconsin, and few will grieve when the last Silphium follows him to the lush prairies of the never-never land.
A Sand County Almanac
Silphium stand out in the prairie, not only because of their enormous size, but because of their interesting attributes.
I didn’t plant Cup Plant in my garden–a seed of it must have been inadvertently buried in a pot of something else that I purchased. Cup Plant (Silphium perfoliatum) is the first silphium to bloom this summer in my garden. A single, large 3 “, lemon yellow daisy opens first, followed a few days later by side clusters of blossoms that bloom in the upper part of 3-8’ tall stems from early-July through August. Like all silphium, there is a charming story to tell about it. Its huge triangular opposite leaves encircle the thick square stem to form a cup that holds rainwater. These little reservoirs provide water for birds, butterflies, dragonflies, and other insects.
Reservoir of rain water in its cup.
Cup Plant is a majestic plant, but I can’t recommend it for small home gardens–not because it is unattractive, but because it is extremely aggressive. I’ve never planted it–but it still appears spontaneously. And it keeps on appearing spontaneously–everywhere. It is a wetland plant, but it grows anywhere in the sun–at least it does in my yard.
I planted 3 Rosin Weed in my new side yard garden many, many years ago. Unbelievably, a few weeks later, one night a car pulled into my driveway, then turned and drove down my sidewalk and ran over my entire side yard garden. Prairie plants, fortunately, are tough. and while they were all broken, none were killed–they were just shorter that year. The Rosin Weed, since then, has increased exponentially–I now have dozens and dozens in every sunny garden in my yard.
Clusters of large, canary yellow daisies bloom at the top of the stems in July and August. The rough, sandpapery, stalkless leaves are arranged in pairs along the length of the stiff stems. In the prairie, Rosin Weed grows 2-4’ tall; in my garden, it is over my head. (If you want a shorter plant, cut the stems back hard at the end of May.–or run them down with your car.) It’s called Rosin Weed because it produces resin along the stems and on the flower stalks that Indian and pioneer children used to chew like gum.
Like many other sunflowers, the blossoms of Compass Plant (Silphium laciniatum) turn toward the sun, from east to west. The 3-4” golden blossoms bloom alternately along the top half of the 3-9’ tall stems from early July through mid-to late August. The most striking feature of this plant, however, is its magnificent, oversize oak leaf-shaped leaves. They orient themselves in a north-south position, thus providing a compass in the prairie for native tribes and early settlers.
While Compass Plant has a deep taproot, small rhizomes extend from the taproot to create colonies. Within the last few years, my Compass Plants have formed a huge colony–much too large for the space it’s in. While these leaves are upright, most of them have splayed out awkwardly–a most unnatural position.
In nature, in the prairie, Compass Plant is scattered here and there, This is at Schulenberg Prairie at Morton Arboretum.
Compass Plant also grows in scattered locations in Christ the Lord Lutheran Church prairie just west of Elgin.
The enormous, rough, spade-shaped basal leaves of Prairie Dock (Silphium terebinthinaceum) are a spectacular presence in the garden and in the prairie. Its smooth leafless stalks rise up to 10’ or more; a cluster of yellow daisies begins to bloom at the top of each stalk the 3rd or 4th week in July.
Prairie Dock is also remarkable for its large, deep taproot, says Suzanne Masi, in her comprehensive book, The Sunflower Family in the Upper Midwest. She goes on to quote Russell Kirt by telling us that its roots can penetrate to the water table, reaching depths of 14 1/2 feet or more and enable the plant to survive during periods or extrme drought.
Arrange it at the front of a garden as an accent; one can easily see through the tall stems.
It makes a striking focal point in the prairie garden from early spring through late fall and into the winter, as the leaves turn from green to gold to a gorgeous red-mahogany. Hold your hands on both sides of the leaf–it will feel cold no matter how hot the day. It’s not nearly as aggressive as the other members of its genus–I planted three of them 15 or so years ago, and I now have five.
Its leaves are stunning in the prairie, as well. This is next to the path at Schulenberg Prairie at Morton Arboretum.
In a prairie garden, Silphium are at their best when planted singly, here and there, in dry-mesic to mesic soil. It’s important to give them lots of competition, such as Aster ericoides and Aster laevis, Eryngium yuccifolium, Euphorbia corollata, Liatris spicata, Dalea purpurea, Monarda fistulosa, Parthenium integrifolium, Ratibida pinnata, Solidago rigida, Sporobolus heterolepis, and maybe a few Coreopsis palmata, Coreopsis tripteris, and a couple of Sorghastrum nutans–beware though–these last three are aggressive species.