Notes from the Naturalist: Curtis Prairie Late Summer


A burst of yellow, and shades of purple and red, herald the coming of fall each year in Curtis Prairie. As we entered the prairie, hundreds of blooming Canada or common goldenrod (Solidago canadensis) waved in the wind greeting us. The first person to ask about them was one young visitor who stood about eye-level to these plants that average about five feet tall. We all noticed how the goldenrods formed in dense clumps, dominating large areas. How do these dense stands form? The group came up with following two possibilities: the plants produce lots of good seeds and/or they may be growing vegetatively (growth from the roots or rhizomes of a “parent plant”). Indeed goldenrods will do both – produce lots of seeds, and, in the right conditions, the original plant will grow many new stems (called ramets) each year, sometimes reaching up to 30 feet in each direction.

Just like the plants themselves, the flowers of goldenrods are typically densely packed. And, their bright golden yellow color that drew our attention also attracted quite a variety of other animals. Leaning a bit closer to the flowers, we could see a variety of bees, wasps, flies, and a few beetles. Butterflies and moths will also nectar on goldenrods. Caterpillars, aphids, and other small insects eat the leaves and stems. Wasps, spiders, praying mantis, lacewings, ambush bugs, assassin bugs, beetles, and birds prey on the insects goldenrod attracts. This unquestioned popularity in the insect and avian world doesn’t always hold for humans. The aggressive spreading capabilities of goldenrod, lead some of us to view a few goldenrod species as weeds. This is true for common goldenrod in this country as well as in various places around the world – where goldenrods species exported from North America are crowding out native plants and spreading and reproducing in natural areas. Sound familiar?

Unlike the flowers of the goldenrod, the flowering parts of grasses in the prairie, such as Indian grass (Sorghastrum nutans) and big bluestem (Andropogon gerardii) are small enough that many of us may not have noticed that they are also flowering now. Bring a magnifying lens to appreciate these little flowers. As far as I know, they never needed to attract our attention or any pollinators’ attention. The flower heads of the Indian grass are chestnut brown. Attached to these chestnut spikes hang little quarter inch fringes of pollen. Their color is unique. It’s a rich light yellow – like they had been dipped in liquid sunshine and hung out to dry. Actually, they are hung out to get ready to take a ride with the wind. Looking through your magnifying lens you can also see little hairs on the flower heads that look like feathered antenna. These hairs will catch the wind borne pollen from other Indian grass plants. Big bluestem, the other dominant grass on the prairie, is also in bloom this time of year. Its flower head has a darker deeper purplish-brown color. Throughout the plant in fall, you will also see various shades of blue, purple, red, and green on the stem – hence the name for this plant that can grow up to eight feet tall – big bluestem. The other common name for this plant is turkey-foot, as the seed heads often grow on three points similar to the shape of a turkey’s footprint.

Other late summer and fall bloomers on the prairie were deep purple to pinkish- purple flowers of New England asters (Symphyotrichum novae-angliae), and, on the western end of the prairie, purple coneflowers (Echinacea purpurea). In central Curtis Prairie and along the edges of the oak tree savanna areas we saw a plant named flowering spurge (Euphorbia corollata). On multiple stems of this 2-3 feet tall plant is what look like sparse bouquets of five-petaled white flowers. This is another plant you may want to have a magnifying lens on hand for. The white “flowers” are actually a bract or modified leaf that often surrounds flower petals before they bloom and can later be noticed beneath the flowering petals. On this plant there are no true petals – the tiny male and female parts emerge in the middle of the bract. Without a lens, it is difficult to see these reproductive parts. We did readily notice that some stems contained the white bract and reproductive parts, while other stems on the same plant may still have retained the bracts, but not the reproductive parts as they had already gone to seed – forming small, round green seedpods.

A plant we saw frequently today did have true tiny white flowers, and lots of them. It began blooming in late July/early August and will be in bloom through September. It is white snakeroot (Ageratina altissima). It is usually about 2-3 feet tall, has sturdy triangular leaves with noticeable veins and a jagged toothed edge. It has many branches bursting with bunches of very compact tiny white flowers with white hair-like fuzz that are actually the thread-like styles (female parts) protruding above the flower petals. You have probably seen this plant somewhere – it’s the plant that is famous for causing the “milk sick” transferred from cows’ milk to humans that many believe poisoned Abe’s mother, Nancy Hanks Lincoln. At that time, it would have been hard to prove – but we do know that the compounds in this plant can be anywhere from irritating to deadly for many mammals. Snakeroot was, and probably still is, in many a pasture. It is also adapted to withstand considerable shade. So, you may see it in your backyard, along the roadside, in parks, and throughout natural areas like the Arboretum.

Especially on the western half of the prairie, we saw the last blooms of some plants that aren’t nearly as common as snakeroot. In the late 1940’s in his famous book, A Sand County Almanac, Aldo Leopold wrote that he would go to a small patch in the corner of an old cemetery to see … “a man-high stalk of compass plant or cutleaf Silphium, spangled with saucer-sized yellow blooms resembling sunflowers.” He continued, “It is the sole remnant of this plant along this highway, and perhaps the sole remnant in the western half of our country. 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.” Many times I pass by the compass plants and other plants in the Silphium genus and wonder what Leopold would think seeing them at home here. While we still are engaged in a mighty struggle to incorporate the ethics and mindset he modeled for all of us, the Silphiums are rough leaved, bold yellow bursts of sun and soil food that literally and figuratively recall Leopold’s steady application of heart and hand upon the landscape. Over sixty years later, the plant he predicted no one would remember, the compass plant (Silphium laciniatum), is a prominent one on Curtis Prairie. We saw the last of its bloom for the season today, along with two plants that have similar looking flower heads, and sandpaper-like leaf textures, but have very different leaf shapes and sizes: Prairie dock (Silphium terebinthinaceum) and Rosinweed (Silphium integrifolium). The fourth plant in the Silphium family, Cup plant (Silphium perfoliatum), can most reliably be seen on the eastern edge of the prairie just past the pump house on the path that leads into the prairie.

Other late season flowering plants we saw today were the yellow flowers of ox-eye daisy (Heliopsis helianthoides) and stiff goldenrod (Solidago rigida). And, some sure signs of fall were scattered asparagus plants with small round, red fruits and white wild indigo (Baptisia alba) pods splitting open. In the slightly shady, oak savanna areas we saw the tops of pale Indian plantain (Arnoglossum atriplicifolium) and spotted Joe-Pye-weed (Eupatorium maculatum) covered with fluffy filaments, called pappus. They are loosening their grip and getting ready for lift-off with small seeds attached. The oaks were showering us with acorns, which grey squirrels and chipmunks are eagerly collecting. The goldfinches were also very active – whistling out their presence in roller coaster flight over their territories, and plucking apart pasture or prairie thistles (Cirsium discolor) to get at their seeds, and adroitly wobbling in the wind on top of the old flower heads while picking out seeds of the sunflowers and Silphiums. Believe it or not, fall is on its way.

Paul Borowsky
Arboretum naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.