Have You Met the Silphium Sisters?

The Silphium sisters are all bright, cheerful, and incredibly tall. They clearly stand above all others around them and people take notice. The four Silphium sisters at Nachusa Grasslands have similarities because they are part of the same plant family, Asteraceae, but each one has unique differences. Let me introduce them to you . . .

Silphium laciniatum

Commonly know as the compass plant. How did this plant receive its name? Well, see how the leaves alternate and point in opposite directions? The leaf on one side tends to point to the south and then the next leaf on the stalk points to the north.
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This compass plant measures 8 feet tall.

​These perennial plants in the Silphium genus are all known for their great heights. Just how tall is the compass plant? In my research I found different height reports so I decided to measure them myself. I located the tallest plants I could find in Nachusa's prairie and discovered the plants ranged in height from about 8 feet to 9 feet tall. Wow! Even more amazing is how deep the root descends into the ground. Are you ready for it? The Illinois Natural History Survey reports a depth of 10-15 feet! Amazing!

Silphium perfoliatum

Commonly know as the cup plant. Notice how the leaves of this second Silphium sister are opposite each other and join together at the stem to form a ‘cup–like’ shape.

Yes, just like a cup, the Silphium leaves can hold water. See the water collecting in the depression at the base of the stem? Birds will often sip the water from this tiny pool. 

The stem is unique from the other Silphiums because it is hairless and square–shaped.

What a fun surprise! Here's a tree frog nestling in the cool water.

Silphium terebinthinaceum

Commonly know as prairie dock. This Silphium sister can be instantly recognized from the others by its enormous leaves. Touch the leaves. They are rough, feeling like a piece of coarse sandpaper. Then slender stems emerging from the base of the plant shoot 10 feet skyward, topped with yellow composite flowers.​

Silphium integrifolium

Commonly know as rosinweed. ​Standing around 6 feet tall rosinweed is the shortest in height of the four Silphium sisters at Nachusa. The leaves are rough and the stems have a lot of bristly hair. Rosinweed gets its name from the resin that oozes from its cut stems. The resin is rather gummy, and as a matter of fact, Native Americans used to chew it.

Like the other Silphium sisters, the rosinweed has a taproot that descends 10-15 feet deep. The plant spreads by short rhizomes, so you often see the rosinweed forming a clump, as seen in the above picture.

Where to see the Silphiums
Once the prairie dock, compass plant, cup plant, and rosinweed were numerous across the prairies in Illinois, but as the prairies were removed these plants declined in number. Conservationist Aldo Leopold watched the last Silphium disappear from what was once a vast expanse of prairie, and he wrote this familiar quote:

What a thousand acres of Silphiums looked like when they tickled the bellies of the buffalo is a question never again to be answered, and perhaps not even asked.

​Thanks to the restoration efforts of staff and volunteers at Nachusa, you may actually be able to see a few Silphiums tickle some bison bellies again! From July to September, one or more of the Silphiums will be in bloom. They are so easy to spot in the prairie because of their incredible heights. Look into the prairie fields and road ditches along Lowden Road, between Flagg Road and Naylor Road. The Silphiums are quite a treat to see, so let's see if you can meet all four sisters!

Today’s author is Dee Hudson, a photographer for Nachusa Grasslands. To see more prairie images, visit her website at www.deehudsonphotography.com.