Sawtooth Sunflower
Helianthus grosseserratus
Aster family (Asteraceae)

Description: This native perennial plant is 3-12' tall. Plants in dense colonies are only 3-5' tall, but lone wolf plants can achieve considerable height. The stout central stem is hairless and often reddish in color. There is very little branching, except for a few small flowering stems in the upper half of the plant. The leaves are up to 8" long and 2½" across, lanceolate or narrowly ovate, and slightly to strongly serrate. They have a sandpapery texture, with minute stiff hairs across their surface. The leaves often curl upward from their central veins, particularly during hot dry weather. They are usually opposite below, but become alternate in the upper half of the plant. They taper gradually into slender petioles that are about ½" in length. The yellow composite flowers are about 3-4" across. They consist of 10-25 ray florets, surrounding numerous disk florets. There are often many flowers in bloom simultaneously on large plants. The blooming period occurs from late summer to fall, and lasts about 1-2 months. The root system is fibrous, producing rhizomes that enable this plant to spread vegetatively.

Cultivation: The preference is full sun, moist soil, and fertile loamy soil with high organic content. A clay or gravelly loam is tolerated. Powdery mildew may affect the leaves, but this typically occurs during the fall after the blooming period. Strong wind can cause this plant to blow over in exposed situations. It also requires lots of room because of its large (sometimes huge) size and aggressive tendencies.

Range & Habitat: The Sawtooth Sunflower occurs throughout most of Illinois, except for a few SE counties. It is a common plant. Habitats include moist to mesic black soil prairies, thickets, moist meadows and savannas near rivers or lakes, the base of bluffs, fence rows, and areas along ditches, railroads, and roadsides. This plant thrives in both disturbed and high quality sites, sometimes forming large colonies that exclude other plants.

Faunal Associations: The most common visitors to the flowers are bees, especially long-tongued species. Among these are honeybees, bumblebees, Epeoline Cuckoo bees, Eucerine Miner bees, large Leaf-Cutting bees, and others. Other insect visitors include Syrphid flies, bee flies, butterflies, moths, and beetles. The caterpillars of some Checkerspot butterflies (Chlorsyne spp.) feed on the foliage, while Sunflower Borer Moths (Papaipoma spp.) eat the pith of the stems. These and other insects feed on this and other sunflowers. Many kinds of upland gamebirds, songbirds, and rodents eat the seeds. These animals probably help to distribute the seeds. Beavers and muskrats may use the stems to construct dams or lodges when this plant is near bodies of water. Large mammalian herbivores, such as White-Tailed Deer and cattle, may browse on larger plants, while groundhogs and rabbits are more likely to attack smaller plants.

Comments: Notwithstanding its name, this sunflower often has leaves that are only slightly serrate. There is considerable variation in the size of plants across different locations, and the leaves are variable in their size and shape. This sunflower can be distinguished from others by the smooth reddish stems, which often have a powdery white bloom that can rub off (i.e., they're glabrous and glaucous). The base of the stems on older plants become slightly woody in appearance. The Sawtooth Sunflower is similar in size and appearance to Helianthus giganteus (Giant Sunflower), but the former species has longer petioles, hairless stems, and often occurs in drier habitats, such as mesic prairies.