The Forsaken Flora

Ever wonder, as you're cruising along the interstate at 70+ mph, what plants are growing in the harsh environment created by asphalt-induced higher temperatures, vehicle-created winds, and runoff including road maintenance chemicals?  If you're like most people, probably not... there are plenty of other things to think about, like talking on cell phones, eating, and putting on make-up.  But if you're like me, observing the highway flora is a top priority.

Fetid Marigold thrives in a narrow band along the highway shoulder

Here in the Great Lakes region, our highway flora consists of an interesting assemblage of plants native to the Atlantic coast, plants native further west and south of here, opportunistic Midwestern natives, and your typical Old World weeds.  One of the most conspicuous is the low-growing, malodorous composite that forms a yellowish- to reddish-colored band immediately adjacent to the highway shoulder.  This is Fetid Marigold (Dyssodia papposa), a plant native through the Great Plains south to Texas, but introduced in the eastern and western thirds of the country.

Not much else grows in the zone with Fetid Marigold

Fetid marigold is so named because of the characteristic strong, unpleasant odor that is emitted from the glands on the phyllaries (you can see these glands in the photograph below).  The Latin name for the genus (Dyssodia) is Greek for "disagreeable odor."  In fact, in the 1800s, C.W. Short included on the herbarium specimen label of one of his collections of this species that "This plant is so abundant, and exhales an odor so unpleasant as to sicken the traveler over the western prairies of Illinois, in autumn."

The orange-colored glands on the phyllaries contain a watery liquid with the characteristic odor of Fetid Marigold

Fetid Marigold has an interesting history in the Chicago Region.  After being introduced to the area in the 1800s, it spread to nearly every road and trail throughout the region.  Between approximately 1930 and 1970, Fetid Marigold nearly disappeared from this area, but beginning in the 1970s, it again began to spread.  Now it can be found along most of our highways.

The habitat in which Fetid Marigold grows is not conducive to the growth of many other species

Another conspicuous composite found along our roadsides is Seaside Goldenrod (Solidago sempervirens).  Unlike the previous species, however, Seaside Goldenrod has been introduced around the Great Lakes region from the Atlantic and Gulf Coast states, where it grows in sandy soils and on the edges of salt marshes near the Atlantic Ocean and the Gulf of Mexico.  I have seen this goldenrod thriving in tiny cracks in concrete along Lake Michigan in Chicago, where no other plant dares to grow.

Seaside Goldenrod is tall and showy with fleshy, leathery foliage

Of the goldenrods found in the Chicago region, Seaside Goldenrod is one of the most attractive, as its individual flowers are quite large for a Solidago. Seaside Goldenrod has leathery, waxy leaves characteristic of many plants that grow in the harsh conditions adjacent to the ocean, making it well suited for the similarly windy and salty conditions that exist along our highways.

Notice the large flowers of Seaside Goldenrod

Saltmarsh Aster (Aster subulatus, or Symphyotrichum subulatum) has similar native and introduced ranges in the United States to those of Seaside Goldenrod, and the two are often found growing together.  Known locally in the Chicago region as Expressway Aster (for obvious reasons), this aster is somewhat inconspicuous, as it has very short light lavender ray flowers that are not much longer than the phyllaries.  It is an annual aster with smooth and somewhat succulent stems and leaves.

Saltmarsh Aster has short (but obvious) ray flowers

Saltmarsh Aster appears late in the season but can form near monocultures in places of high salinity.  At a location I visited for work twice in 2011, it was undetectable during my June visit, but abundant when I was back at the site in September.

Near monocultures of Saltmarsh Aster can be formed in moist to wet areas with high salinity

Another annual aster that grows in the salty zone along our highways in the Great Lakes region is Rayless Aster (Aster brachyactis, Brachyactis ciliata, or Symphyotrichum ciliatum).  Unlike the previous two species, Rayless Aster is native in the western United States and Canada, as well as in Eurasia.

Rayless Aster can be somewhat inconspicuous

Rayless Aster is probably the most inconspicuous of the species in this post, especially because its ray flowers, as the common name implies, are absent or undeveloped.  However, when in fruit, the fluffy pappus is quite noticable.

Although the ray flowers are lacking, the spreading involucral bracts are helpful in the identification of Rayless Aster

This just scratches the surface regarding some of the plants that make their home in one of our harshest environments.  Although all of these plants are non-native around the Great Lakes, they perform the difficult task of growing in an area that is too salty, windy, and sediment-covered for most of the other plants in our flora to survive, while at the same time going almost completely unnoticed even though they are probably amongst our most frequently seen plants.  Some of the other plants that frequently are found with these four composites in this unique habitat include Quack Grass (Agropyron repens), Common Ragweed (Ambrosia artemisiifolia), Hairy Aster (Aster pilosus), Triangular-leaved Orach (Atriplex prostrata), Expressway Sedge (Carex praegracilis), Oak-leaved Goosefoot (Chenopodium glaucum), Chicory (Cichorium intybus), Horseweed (Conyza canadensis), Queen Anne's Lace (Daucus carota), Barnyard Grass (Echinochloa crusgalli), Tall Fescue (Festuca arundinacea), Squirrel-tail Grass (Hordeum jubatum), Burning Bush (Kochia scoparia), Willow Lettuce (Lactuca saligna), Salt-meadow Grass (Leptochloa fusca var. fascicularis), Purple Loosestrife (Lythrum salicaria), Knee Grass (Panicum dichotomiflorum), Common Reed (Phragmites australis), Sidewalk Knotweed (Polygonum arenastrum), Alkali Grass (Puccinellia distans), Alkali Bulrush (Scirpus maritimus var. paludosus), Green Foxtail (Setaria viridis), Lesser Salt Spurrey (Spergularia marina), Sheathed Rush Grass (Sporobolus vaginiflorus), Sea Blite (Suaeda calceoliformis), Narrow-leaved Cattail (Typha angustifolia), and Hybrid Cattail (Typha x glauca).

If you're ever in search of a new county or state record, I recommend looking for these rapidly spreading highway plants.  Three of the species above were new county records where I found them in Dane County, Wisconsin a few weeks ago.