Dogbane family (Apocynaceae)
Description: This is a native perennial plant from 2-5' tall. Initially, there is only a central stem as this plant develops during the spring, but it eventually forms multiple stems and acquires a shrubby appearance. The opposite leaves are about 3" long and 1½" wide, with an ovate shape and smooth margins. The petioles are usually rather short, and the stems often have a reddish tint. The sap in the leaves and stems is milky and toxic.
Numerous clusters of small white flowers, sometimes with pinkish accents, occur at the ends of the smaller stems. Each flower is less than ¼" long, consisting of a shallow tubular corolla with 5 slightly flared lobes. The blooming period occurs during early to mid-summer for about 1½ months, and sometimes this plant will bloom again during late summer if it has been damaged and prevented from having flowers earlier in the year. The flowers often produce a strong jasmine-like scent. The skinny seedpods are about 8" long and occur in pairs, which eventually open up along one side during the fall to allow the brown seeds to be dispersed by the wind on their white tufts of hair. The root system consists of a taproot and long rhizomes that can form substantial colonies of this plant.
Cultivation: The preference is full sun and moist to mesic conditions. This plant grows best in fertile loamy soil, but it will also tolerate soil that contains some clay or gravel. Neither standing water from spring rains nor summer droughts bother it, although some of the lower leaves may turn yellow and fall off in response to the latter. Some shade is also tolerated, although flowering will be less abundant. In moist locations, this plant can be quite weedy and aggressive.
Range & Habitat: Common Dogbane occurs in every county of Illinois and is quite common. Habitats include moist to mesic black soil prairies, thickets, moist meadows near rivers, woodland borders and savannas, limestone glades, abandoned fields and pastures, vacant lots, junk yards, and along roadsides and railroads. This plant favors disturbed areas, but also occurs in high quality habitats.
Faunal Associations: The nectar of the flowers attract many kinds of insects, including including long-tongued and short-tongued bees, Sphecid wasps, butterflies, skippers, and various kinds of flies. Flies are especially common around the flowers, and include Syrphid flies, Bee flies, Tachinid flies, Blow flies, Muscid flies, and Anthomyiid flies. However, they are not very effective pollinators. The caterpillars of several moths feed on the foliage of Common Dogbane, including Cycnia tenera (Delicate Cycnia), Cycnia oregonensis (Oregon Cycnia), Spargaloma sexpunctata (Six-Spotted Gray), and Hemaris diffinis (Snowberry Clearwing). The latter species is a day-flying mimic of wasps. The colorful Chrysochus auratus (Dogbane Leaf Beetle) also feeds on the foliage. Mammalian herbivores avoid eating this plant if other kinds of food are available because the foliage and stems are highly toxic. There have been cases of hungry livestock succumbing to fatal poisoning from this plant.
Photographic Location: The photograph was taken at a fence row near Urbana, Illinois.
Comments: The flowers are strong attractors of butterflies. Another common name for this plant is Indian Hemp, because native Amerindians derived a strong fiber from the stems, which was used as twine in basketry, mats, and other artifacts. Some early French explorers remarked upon the abundance of this plant in the original prairie, which they referred to as 'hemp' in their writings.