Summer Roadside Weeds in the Midwest

Many roadside weeds common in the midwest have yet to make it in any numbers to eastern locales like Princeton, NJ. Unless differences in climate or soil are limiting these nonnative weeds' rampancy in the east, a trip to the midwest can feel like prelude for what eastern roadsides could look like decades from now. Even if they can't compete with tough customers in NJ like the nonnative mugwort and Japanese knotweed, their behavior along midwestern roadsides shows what those first few popping up in Princeton could turn into over time. 

Here's a display of roadside weeds collected on the hood of my rental car at a rest stop. This was in Ohio, though the same roadside weeds are found in Wisconsin, Michigan, and likely other midwestern states as well. The row of blue flowers on the left are chicory. The delicate white disk of Queen Anne's lace--the wild version of the carrots we eat--is in the upper right. Yellow sweet clover--there's also a white version--is in the lower right, and the pink flower in the middle is spotted knapweed.

All of these, which seem so modest when they first show up, can ultimately form dense stands along roadsides in the midwest, as can other non-natives like the tall, dramatically shaped teasel, 

and the Canada thistle whose tops become thick with fluffy seeds this time of year (see photo). 

Less common are the tall yellow spires of wooly mullein, which in most patches appear less exclusionary in their growth habit.

One super-invasive found along roadsides in both the east and the midwest is Phragmitis--the towering "common reed" with large plumes on top that forms dense stands in ditches, displacing the native cattails. Driving on I-94 around Ann Arbor, MI, I noticed dead stands of Phragmitis--evidence they have been sprayed to save the patches of cattails the Phrag was invading. That's the first evidence I've ever seen of selective use of herbicide for restorative purposes along a freeway. 

Another nonnative I keep an eye out for, both in Princeton and the midwest, is birdsfoot trefoil. Mostly it appears as small patches of yellow in a lawn or along a roadside, but I found one instance in Ohio that shows its potential to spread and dominate, coating a large area, much like crown vetch has done where it was extensively planted for erosion control along freeways in Pennsylvania. 

What grows along roadsides can spread to grasslands being actively managed for native species. We were pulling spotted knapweed out of prairies in Ann Arbor in the 1980s. I once witnessed birdsfoot trefoil being assiduously pulled before it could spread across a prairie packed with native diversity at Kishwauketoe--a nature preserve in my home town in Wisconsin. The botanist there knew that a little can quickly turn into a lot, so better to catch those weeds early. 

The vast majority of drivers are oblivious to these roadside dramas, where a pretty flower can become too much of a good thing. For me, a drive through Ohio provides useful guidance for deciding what to weed out of a meadow in Princeton. 

Related post: Stiltgrass Reaches Michigan -- While midwestern weeds are moving east, eastern uber-invasives like lesser celandine and stiltgrass are just starting to pop up in Michigan.