The Prairie in SummerBy Lois Tilton (LTilton)
August 20, 2008
After a wet spring like we have had this year, the prairie looks like a jungle. Two months after the ground had been burned bare and black, everywhere is burgeoning green. By June, the prairie is covered with flowers, and it will be in bloom continuously until frost signals an end to the growing season. For gardeners planning a prairie garden, it is important to note not only the succession of bloom but also the different families of plants that occupy the prairie.
The Asteraceae family is the most numerous on the prairie. This is the family of the asters and sunflowers, whose composite flower heads have ray flowers surrounding a central disk. A prairie garden would not be complete without several varieties of golden composite flowers in bloom.
As the Mesozoic Era was the Age of Dinosaurs, so high summer on the prairie is the season of the silphiums. These plants dominate the prairie landscape with their huge leaves and golden flowers. Even in spring, their giant leaves are conspicuous as they unfold from the burned earth, from the staghorns of the Compass Plant to the unfurled elephant ears of the Pairie Dock and the deep, broad chalice of the Cup Plant.
In a dry year, the size of these plants is still striking, but in a wet year, their flower stalks may reach eight or ten feet high, taller than you might be able to reach. Visitors to the prairie may see a field blooming with Compass Plants and take them for sunflowers because of their size and the golden ray flowers. But the distinctive shape of the leaves makes most of the silphiums unmistakable. While some gardeners may not believe they have room for such large plants, their foliage does create interest throughout the year.
Blooming first, in early July, is the Compass Plant, notable for the staghorn shape of its leaves. Its name is derived from the fact that it will often orient its leaves along an axis from north to south.
Compass Plant [Silphium laciniatum]
Cup Plant [Silphium perfoliatum]
The Cup Plant is distinguished by the cup shape of its large, rough leaves, often filled with water after a rain. It is the stoutest of the Silphium plants.
Prairie Dock [Silphium terebinthinaceum]
Prairie Dock sends up a flower stalk often over eight feet in height from its low rosette of broad leaves, resembling the common dock weed. These leaves sprout very early in the spring, making a striking display.
Rosin Weed [Silphium integrifolium]
Rosin Weed is the dwarf of the silphiums, along the lines of a downsized Cup Plant, and it can be quite difficult to distinguish it from several of the sunflowers, as individual specimens can be quite variable. Indeed, I can't entirely guarantee that I have all the sunflowers identified correctly, as even the botanist I consulted was not always sure. One distinguishing characteristic of the Rosin Weed, however, is the extreme sandpapery roughness of its leaves.
The prairie is home to many varieties of true sunflower, some of them rivaling the silphiums for size. The common sunflower [Helianthus annuus] certainly can boast the largest flower head, but these are mostly the cultivated variety; the wild sunflowers are not so massive. The Maximilian Sunflower [Helianthus maximilianii] can grow at least nine feet tall - another prairie giant. It is more typically found further west and south than Illinois, however. On the prairies I frequent, either the true sunflowers are not abundant or I have not been able to identify many varieties.
Sawtooth Sunflower [Helianthus grosseserratus]
A tall, relatively slender sunflower with multiple flower heads on individual stalks near the top of the plant. The leaves are long and narrow, and not excessively sawtoothed as far as I can see.
False Sunflower [Heliopsis helianthoides]
This close relative of the true sunflowers, however, is highly abundant here. It is a mid-sized plant, around four feet high, with single flowers heads on individual stalks. The central disk is more cone-shaped than flat. It spreads readily to make an attractive display.
Another important group of prairie flowers related to the sunflowers. While coreopsis comes in several varieties, from a few inches high to as much as eight feet. Their leaves and stems are usually slender. Anyone planning a prairie garden should certainly consider including this group of plants.
Prairie Coreopsis [Coreopsis palmata]
One of the first yellow-blooming flowers to appear in the late spring prairie, they are a manageable size and make a nice massed display.
Tall Coreopsis [Coreopsis tripteris]
This coreopsis blooms in late summer, along with the silphiums, and in a good season it can reach the same height, although it is noticeably more slender. The photo at the top of this article shows Tall Coreopsis sharing the sky with a clump of Cup Plants.
BLACK-EYED SUSAN [Rudbeckia hirta]
Another very common yellow-flowered plant of the summer prairie, Rudbeckia is one of many that take the form of a coneflower, with the central flower disk raised to a cone shape. R. hirta is the most common species, although other varieties have been cultivated for the garden. It is usually about two feet high and has a long blooming season., making it another mainstay of the prairie garden, as it makes an attractive mass display and spreads readily.
This plant is variously known as the Gray-headed Coneflower or the Yellow Coneflower, although there seems to be a more uncommon species of Echinacea also known as the Yellow Coneflower. It is a very striking plant in massed groups, as it grows about four feet in height, with a slender stem and leaves. The drooping shape of its petals below the tall central cone make this one easy to distinguish among the many varieties of yellow composite flowers on the summer prairie.
Not all the composite flowers of the prairie are yellow. Some of the most common species are white, but these are not always the most desirable. The fleabanes can be found in bloom everywhere on the prairie throughout the summer. They are annual plants, unlike most of the species of the prairie, and some [like myself] consider them weedy. I tend to pull them out of my own garden.
Daisy Fleabane [Erigeron strigosus]
This plant grows to around two or three feet in height, bearing many clusters of small flowers with yellow centers surrounded by many fine white ray flowers. It is sometimes a biennial. Common or annual fleabane [E annuus] has coarser, hairier leaves, is often found in waste places and is generally more likely to deserve the name of a weed.
Yarrow [Achillea millefolium]
Some prairie managers consider this plant a weed but it is very commonly found in the early summer, along with the fleabanes and ox-eyed daisy, when the prairie landscape is briefly dominated by white. Its name comes from its fine-cut ferny leaves, and the flower head is rather flat, with a multitude of small compound flowers. It spreads very readily, to the point of being invasive.
OX-EYED DAISY [Leucanthemum vulgare]
This one is generally agreed by all the prairie experts to be a weed, an undesirable non-native plant. Nonetheless, they are very common on all but the most stringently-controlled prairies, appearing in early summer with the fleabanes and yarrow. Heretically, I find them neat and cheerful, the reverse image of all the yellow composite flowers, and I tend to keep them in my own garden while pulling out the fleabanes. Always remember - the garden is yours, and you should plant what pleases you, unless you are really dedicated to strict authenticity.
There are relatively few purple flowers on the early summer prairie, so the purple coneflowers stand out, even individual specimens, and they are stunning in a massed display. These are the plants most commonly throught of as coneflowers, although the term is applied to many different composite flowers with a high central disk instead of a flat one. Echinaceas have been widely cultivated as garden ornamentals, with new varieties in different colors.
Purple Coneflower [Echinacea purpurea]
The most well-known echinacea. Plants can reach five feet in height with multiple flower heads.
Pale Purple Coneflower [Echinacea pallida]
Compared to the Purple Coneflower, this species has thinner leaves and its ray petals are likewise thinner and droop conspicuously.
WILD QUININE [Parthenium integrifolium]
This plant does not appear at first glance to belong in the aster family, as the ray flowers are so small and sparce as to almost be invisible. The flower heads are small, clustered together, and a brilliant, pure white. It is a mid-sized plant, not much more than two feet in height.
The legume family, including the clovers, is another of the most important groups of plants on the prairie. They are mostly low-growing plants, although some may send up taller flower stalks. The flowers share the distinctive shape of peas and beans, and come in a wide variety of colors. The plants in this family have compound leaves, some very finely cut, and some have tendrils.
LEAD PLANT [Amorpha canescens]
One of the most common prairie plants, that gardeners should certainly consider when planning a prairie garden. The distinctive compound leaves are a fuzzy grayish color, from which its common name is derived, and the stems are somewhat woody. A tall raceme is covered with tiny dark purple flowers in midsummer.
In early summer, this group of plants blooms in a variety of colors on tall racemes. The flowers are large and greatly attractive to bumblebees. The indigos all produce large black seed pods which provide interest even after they have bloomed.
Blue Wild Indigo [Baptisia australis]
This is a very ornamental plant with attractive blue flowers on a mid-sized, bushy plant about three feet in height.
White Wild Indigo [Baptisia leucantha/Baptisia alba]
The white species of wild indigo is somewhat taller than the blue, with flower spikes that can reach five feet.
The prairie clovers are very important for most restoration projects. They may not seem very clover-like to the casual observer, who may be used to the rounded flowerhead of cultivated species. The prairie clovers bloom on a short spike that looks like an elongated cone with a band of tiny individual flowers, beginning at the bottom and rising gradually to the top. A single plant appears insignificant, but an early summer meadow blooming with prairie clover is a delight, and like all clovers they are highly attractive to bees. The flower stem reaches about two feet in height, with slender leaflets.
Purple Prairie Clover [Dalea purpura/Petalostemum purpureum]
The bright purple flower heads make this plant really stand out in bloom. It should be planted for a massed display.
White Prairie Clover [Dalea candida /Petalostemum candidum]
Except for the color and slightly broader leaflets, the white prairie clover is very similar to the purple variety.
The milkweeds are another very important family at home on the prairie. They are all extremely attractive to bees and butterflies, and many species are quite ornamental, with flower clusters in a variety of bright colors. Some, in addition, are delightfully fragrant. There is a great variation in size among the milkweeds, from the tall, coarse growth of the Common Milkweed [Asclepias syriaca] to the Narrow-leaved Milkweed [A stenophylla]. Many of these would make an excellent addition to a prairie garden.
Common Milkweed [Asclepias syriaca]
A tall plant with several rose-pink flower clusters. While gardeners often plant it for the sake of the Monarch butterfly, it can be invasive; other species may be preferable.
Prairie Milkweed [Asclepias sullivantii]
This species is similar to Common Milkweed, but its flowers are a darker pink and larger.
Butterfly Milkweed [Asclepias tuberosa]
Also known as Butterfly Weed. The bright orange flowers make this one of the most striking plants on the prairie. It is a low, spreading plant, no more than two feet in height. As the name suggests, it is very attractive to butterflies and nectar-loving insects. Prairie gardeners should certainly consider this one.
There are many other individual species of forbs at home on the prairie, although they may not belong to the more important families of prairie plants.
Meadow Anemone [Anemone canadensis]
A low-growing plant with white flowers in early summer that form an interesting conical seedhead. A member of the buttercup family.
Virginia Anemone [Anemone virginiana]
Sometimes also known as Thimbleweed or Tall Anemone, from the shape of its seedhead. Another inconspicuous early summer flower.
Culver's Root [Veronicastrum virginicum]
An important plant in the midsummer prairie landscape, mid-sized, with a tall spike covered in small white flowers that bloom first at the bottom of the spike and then move upward.
Foxglove Beard Tongue [Penstemon digitalis]
A delicate white tubular flower on a plant that grows to about three feet. It prefers a more moist and shady location.
Prairie Dogbane [Apocynum cannabiunum]
A tall, shrubby plant with attractive leaves and small white flowers in early to midsummer. This one can spread vigorously and may need to be cut back.
Spiderwort [Tradescantia ohiensis]
Common Spiderwort has dark blue flowers that bloom only for a day on plants two to three feet in height. Despite its attractive color, it is not very conspicuous as a single specimen and should be planted in groups.
Rattlesnake Master [Eryngium yuccifolium]
One of the most striking and exotic plants in the paririe landscape, Rattlesnake Master is almost cactus-like, with thick, waxy, sharply-toothed leaves that resemble a yucca, whence its name. The flower heads form a spikey ball at the top of a tall stem, but this one is interesting throughout the year.
Wild Bergamot [Monarda fistulosa]
Also known as Bee Balm from its attractiveness to bees. One of the most important flowering plants on prairie. In midsummer, entire meadows can be lavender with bergamot flowers. A must for the prairie garden.
My excursions to the prairie this summer for the purpose of this article have been a real delight. Whether or not you are planning a prairie garden, if you live in the center of North America, you might consider making a visit to a nearby prairie preserve to see for yourself the variety of plants growing there.
Most of these photos were taken in the Russell R. Kirt Pairie of the College of DuPage and preserves managed by the DuPage Country Forest Preserve District, whose botonists and naturalists I have bugged to help in identifying these plants. Any mistakes in identification are probably my own fault.