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Silphiums: Standing tall over the prairie


This past month I have been traveling on the road more hours than I care to count. The time in the car has allowed for some windshield botany. Better described as identifying plants while going over 65 miles per hour.

Many invasive species stand out as my brain has been wired to spot those for purposes of eradication. Teasel (Dipsacus laciniatus and Dipsacus sylvestris) and purple loosestrife (Lythrum salicaria) was the most prevalent in my travels from Illinois to Michigan. Around St. Louis, teasel was another top weed spotted along with escaped ornamental pear (Pyrus calleryana).

Despite the weeds, there was one group of native plants that stood out above the rest, mostly because they are some of the tallest prairie species, the Silphiums.

Silphium is a genus (the first name in the Latin species name) that is home to four plants that no tallgrass prairie should be without. Compass plant (Silphium laciniatum), Cup plant (Silphium perfoliatum), Rosinweed (Silphium integrifolium), and my favorite Prairie Dock (Silphium terebinthinaceum).

These four plants share similar traits that make them easy to identify when traversing the prairie, which is a reason I like this genus. All four plants have rough almost sandpaper-like leaves. The harsh texture of these leaves is caused by stiff hairs on the upper and lower leaf surface.

The shortest of the silphiums tends to be rosinweed, growing up to five feet tall. Prairie dock and cup plant can grow up to ten feet, while compass plant towers above the prairie at twelve feet tall. The height of these plants is mostly due to the flower stalks which raise bright yellow sunflower-like blooms above the grasses and other native forbs. The flowering stems bear multiple blooms along its length. Compass plant for my money tends to give the best flower display.

The coarse nature and size of silphiums give these plants a bit of a prehistoric look as they stand out against the prairie grasses. The ease in identifying silphiums is an excellent gateway into learning about prairies and can make you sound quite impressive during parties.

You can help your trivia team by knowing that compass plant derived its name because the leaves tend to line up in a north-south direction. While pioneers relied on this belief, it is not always dependable as I've found a few times in the prairie.

Cup plant is aptly named due to its rigid leaves that emerge and surround the stem and holds water after rain. I love it when a plant name makes sense!

Prairie dock has large spade-shaped leaves that can be 18-inches long and 12-inches wide! These leaves emerge on long six-inch stalks. Picture hosta, but more battle ready like a 1980s movie action hero. Though the leaves are shorter than most of the surrounding plants, prairie dock still competes successfully, while sending up 12-foot flower stalks as a great signal to the plant's whereabouts.

Are you interested in learning more about native plants, wildlife, or conservation? The University of Illinois Extension leads the Master Naturalist program. A group of volunteers who wish to promote the stewardship and conservation education of our natural world. If you would like more information on becoming a Master Naturalist please contact your local county Extension office and visit our website.

One last thing to chew on during long car rides: Did you know silphiums produce a resin that many Native Americans would use as chewing gum? Your trivia team will thank me.


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