Description: This 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 glabrous, glaucous, terete (circular in cross-section), and often reddish or reddish-purple in color. There is very little branching, except for some flowering stems that occur along the upper half of the plant. The leaves are up to 8" long and 2½" across, lanceolate-oblong, and either smooth (entire) or slightly to strongly serrate along their margins. The upper leaf surface is medium to dark green with a sandpapery texture that derives from the presence of minute stiff hairs. The lower leaf surface is pale green and softly hairy. The leaves are often slightly recurved, and they have a tendency to fold upward along their central veins, particularly during hot dry weather. The leaves are opposite below, but they become either alternate or opposite along the upper half of the plant. The leaves taper gradually into slender petioles that are about ½" in length.
The upper stems
terminate into either individual or small clusters
of flowerheads. Each
flowerhead is 2½-4" across, consisting of 10-20 ray florets
that surround numerous disk florets. The
tiny corollas of the disk florets are tubular-shaped and yellow, while
the petaloid rays along the circumference of the flowerhead are bright
yellow and oblong in shape. Around the base of each flowerhead, there
are floral bracts (phyllaries) that are arranged in several overlapping
series. These bracts are light green and linear-lanceolate in shape,
becoming slightly recurved when the flowerhead blooms. On a large
plant,
it is not uncommon for several flowerheads to be bloom at the same
time. The blooming period occurs from late summer to fall, lasting
about 1-2 months. The disk florets are replaced by achenes
about 3-4
mm. in length that are oblongoid and somewhat flattened in shape. The
root system is fibrous and rhizomatous, often forming clonal colonies
of variable size.
Cultivation:
The preference is full sun, moist soil, and fertile loamy soil with
high organic content. However, this robust plant will tolerated other
kinds of soil. 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 native Sawtooth Sunflower occurs throughout most of Illinois,
except for a few SE counties (see Distribution
Map).
It is a common plant. Habitats include moist to mesic black soil
prairies, thickets, moist meadows near rivers or lakes, Bur Oak
savannas, bases of bluffs, fence rows, and areas along ditches,
railroads, and roadsides. Sawtooth Sunflower 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, Cuckoo bees (Epeolus
spp., Triepeolus
spp.), digger bees (Melissodes
spp.), and leaf-cutting bees (Megachile spp.).
Other insect visitors include Syrphid flies, bee flies, butterflies,
moths, and beetles. Both nectar and pollen are available as floral
rewards. Other insects feed on the foliage, plant juices, pith of
stems, developing seeds, etc., of sunflowers. These insect feeders
include caterpillars
of the butterflies Chlosyne
nycteis (Silvery Checkerspot) and Chlosyne
gorgone (Gorgone Checkerspot), stem-boring caterpillars of
Papaipema
necopina (Sunflower Borer Moth) and Papaipema rigida
(Rigid Sunflower
Borer Moth), seed-eating caterpillars of the moths Homoeosoma electella
(Sunflower Moth) and Stibadium
spumosum (Frothy Moth), foliage-eating caterpillars of Grammia arge (Arge
Tiger Moth) and Phragmatobia
fuliginosa (Ruby Tiger Moth), and other moths.
Other insect feeders of sunflowers include the stem-boring larvae of Apion occidentale (Black Sunflower Weevil) and Cylindrocopturus adspersus (Sunflower Stem Weevil), Physonota helianthi (Sunflower Tortoise Beetle) and Systena blanda (Pale-Striped Flea Beetle), larvae of the flies Neotephritis finalis (Sunflower Seed Maggot) and Strauzia longipennis (Sunflower Maggot), Hesperotettix viridis (Meadow Purple-Striped Grasshopper) and Melanoplus femurrubrum (Red-Legged Grasshopper), Aphis helianthi (Sunflower Aphid) and Uroleucon ambrosiae (Brown Ambrosia Aphid), Clastoptera xanthocephala (Sunflower Spittlebug), and many other insects (see Insect Table for a more complete listing of these species). The seeds of sunflowers are a favorite food of such upland gamebirds and songbirds as the Bobwhite Quail, Hungarian Partridge, Mourning Dove, Redwing Blackbird, American Goldfinch, Lark Sparrow, and Savannah Sparrow (see Bird Table for a more complete listing of these species). Such rodents as the Franklin Ground Squirrel, Thirteen-lined Ground Squirrel, Plains Pocket Gopher, Prairie Vole, and Meadow Vole eat the seeds and/or other parts of sunflowers. These animals probably help to spread the seeds into new areas. When the Sawtooth Sunflower and other sunflowers are located near bodies of water, beavers and muskrats sometimes use their stems to construct dams or lodges. Deer, cattle, and other hoofed mammalian herbivores occasionally browse on the foliage of larger sunflower plants, while groundhogs and rabbits are more likely to attack smaller plants.
Photographic
Location:
The photographs were taken at the Red Bison Railroad Prairie in Savoy,
Illinois, and Meadowbrook Park in Urbana, Illinois.
Comments:
Notwithstanding its name, the Sawtooth Sunflower often has leaves that
are
toothless or only slightly serrated. There is considerable variation in
the size of plants across different locations, and the leaves are
somewhat variable in their size and shape. This sunflower can be
distinguished from other Helianthus
spp. (sunflowers) by its smooth reddish stems, which often
have a powdery white bloom that can rubbed off (i.e., they are glabrous
and
glaucous). The lower stems on large older plants can become slightly
woody in appearance. The Sawtooth Sunflower is similar in size and
appearance to Helianthus giganteus (Giant
Sunflower), but this latter species has hairy stems and it is usually
found in habitats that are more moist and sandy.