Wander across a Missouri prairie or glade, or even along a roadside with wet ditches, and chances are you'll spot prairie dock, compass plant, cup plant, rosinweed or starry rosinweed. Each of these Missouri plants is an individual in its own right, but all are related species in the genus Silphium.
These tall, sturdy members of the sunflower family all are perennial plants with sandpaperlike leaves. All have sunflowery blossoms that range from the size of a silver dollar to a saucer. But like many relatives, they have their differences. They claim different territories, and each has developed its own ways to survive.
Silphium is the ancient name of a resinous plant. It was given to this group of plants because of their pine-scented, resinous sap. On a summer hike in most Missouri prairies, you will likely come across compass plant stalks or a clump of rosinweed and find small globs of sap exuding from the stems.
As John Madson writes in Where the Sky Began, "[Pioneers] found that [the compass plant] produced a pretty good brand of native chewing gum. Drops of clear sap exude from the upper third of the stem and solidify with exposure.
It has an odd, pine-resin taste that's pleasant enough, but it must be firmed up before it's chewed. A couple of summers ago I tried some of this sap while it was still liquid. It's surely the stickiest stuff in all creation, and I literally had to clean it from my teeth with lighter fluid."
Cattle, however, seem to have no problem with the sap. As Aldo Leopold writes in A Sand County Almanac, "I once saw a farmer turn his cows into a virgin prairie meadow previously used only sporadically for mowing wild hay. The cows cropped the Silphium to the ground before any other plant was visibly eaten at all. One can imagine that the buffalo once had the same preference for Silphium."
The resinous sap and sandpaperlike leaves of Silphium species may deter some insects or other grazers. The tough leaves also slow transpiration, helping the plants conserve water.
Silphium species have other survival strategies. Aldo Leopold's admiration for the tenacity of compass plant is apparent in his "Prairie Birthday" essay in A Sand County Almanac:
"Silphium first became a personality to me when I tried to dig one up to move to my farm. It was like digging an oak sapling. After half an hour of hot grimy