The Native Plant Garden: Pruning Prairie Dock Prevents Problems

As its name proclaims, Prairie Dock (Silphium terebinthinaceum) is native to the tallgrass prairie of North America, and is a must have for the sunny native plant garden.  The spade shaped leaves are big and bold – a nice contrast to the grasses and other prairie plants – the look is almost tropical.  And the flower stalks on Prairie Dock can get wicked tall, 6 to 8 feet tall. 

For the first couple of years, I looked forward to this amazing feat, as the flower stalks grew taller and taller on the Prairie Dock planted along my driveway.  It would be the end of August, and just as the flowers began to open, a windy summer storm would move through and take down the stalks, leaving them sadly leaning at a 45 degree angle.  And, always, they fell towards my neighbor’s driveway. No good.  It was bad enough, true to their name, that all of the flowers faced south, towards the sun and my neighbor, and away from my view.

I could have staked the stems.  Too much work.  I decided to just cut off the flower stalks when they began to emerge in early July – the flowers where nice, I thought, but just did not work in a garden setting – the stems got too tall for their own good.  To my surprise, a new set of flower stems soon began to re-grow from the plant. 

These, however, never got as tall (only 4 feet or so) and therefore did not get so top heavy as to flop over in a wind storm.  Incredibly, they flowered at the same time as the Prairie Docks in my backyard meadow that were not cut back – and they looked great – more flowers than on the taller stalks – bonus!

The stems were cut back to the base of the plant.  As mentioned, the flower stalks could also be tied to stakes driven into the ground to help support them, but I actually like the shorter flowers stems in the garden setting that result from the early July pruning.