Maximilian's Sunflower Helianthus maximilianii Aster family (Asteraceae)

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Description: This adventive perennial plant is 3-8' tall and largely unbranched, except where the flowers occur. The central stem is stout, round, light green to light red, and densely covered with short white hairs. The leaves occur alternately along the central stem, except for some of the lower leaves, which may occur oppositely from each other. These leaves are up to 12" long and 2" across. They are sessile against the stem, and narrowly lanceolate. Their upper and lower surfaces are light green and covered with fine white hairs. The margins of the leaves are smooth, or they may have widely spaced small teeth. Furthermore, the typical leaf folds upward from the central vein, and curls downward from the stem on account of its length. From the axils of the upper leaves, there are short flowering stalks. Each of these stalks is more or less erect, bearing a single composite flower and possibly 1 or 2 leaves. Each composite flower is about 2–3½" across. There are 20-40 yellow ray florets, which surround numerous disk florets. Behind each composite flower, there are green bracts that are lanceolate or narrowly lanceolate; they are covered with fine white hairs as well. The blooming period is late summer to fall and lasts about 1 month. The achenes are linear-oblong with a pair of awns on top. They are blown about by the wind, or distributed by animals. The root system consists of fleshy, fibrous roots and rhizomes. Like other perennial sunflowers, this plant can form vegetative colonies.

Cultivation: The preference is full sun and mesic to dry conditions. The soil can contain clay-loam, rocky material, or loess. This plant appears to have few problems with pests or foliar disease. It can grow tall and spread aggressively, and may flop over while in bloom if it is grown in moist rich soil.

Range & Habitat: Maximilian's Sunflower is an uncommon plant that occurs in NE Illinois, west central Illinois, and SW Illinois (see Distribution Map). It is adventive from the west in most, if not all, of these areas. It is possible, however, that Maximilian's Sunflower is native to a few of the western counties where it occurs in high quality natural habitats. Habitats include rocky upland prairies, loess hill prairies, ledges of rocky cliffs, areas along railroads and roadsides, and waste ground. This plant is more common in states that lie west of the Mississippi River.

Faunal Associations: The flowers of this species probably attract many of the same insects as other sunflowers, including long-tongued bees, short-tongued bees, butterflies and skippers, and beetles. These insects seek nectar or pollen. The seeds of sunflowers are an attractive food source to both birds and small mammals (see Wildlife Table). The caterpillars of the butterfly Chlosyne nycteis (Silvery Checkerspot) feed on the foliage, while the caterpillars of several Papaipema spp. (Borer Moths) bore through the stems (see the Insect Table for additional species that feed on sunflowers). The foliage of young plants may be eaten by rabbits and groundhogs, while large plants are eaten by livestock.

Photographic Location: A city park in Champaign, Illinois, where a colony of plants occurred along a small lake.

Comments: Maximilian's Sunflower is named after an early botantical explorer of North America. This plant has attractive foliage and flowers, and it is easy to identify because of the unusual leaves. These narrow leaves are longer (up to 12") than the leaves of other Helianthus spp. in Illinois, and they have a distinctive light green or greyish green appearance because of their fine white hairs. Two native species, Helianthus grosseserratus (Sawtooth Sunflower) and Helianthus giganteus (Giant Sunflower), also have narrow leaves, but they are not covered with dense white hairs. Another species resembling Maximilian's Sunflower is Helianthus salicifolius (Willow Sunflower), which occurs in the southern Great Plains. The Willow Sunflower has narrow leaves that are even longer than Maximilian's Sunflower, but they are only ½" across or less. The Willow sunflower is not known to occur in Illinois at the present time, although a colony of 500 plants once existed in Cook County before it was destroyed by commercial development. These plants were undoubtedly adventive from the west.

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