Helianthus × luxurians
Aster family (Asteraceae)
Description: This herbaceous perennial wildflower is 3-8' tall and unbranched, except toward the apex where the flowering heads occur. The central stem is terete, light green or dark red (often the latter), and sparsely covered with stiff bristles. The middle to upper leaves are alternate, while the lower leaves are either alternate or opposite; they are up to 7" long and 1¼" across. The leaves are narrowly lanceolate and slightly toothed along their margins; they have short slender petioles up to ½" long. The upper surface of each leaf is rough-textured, while the lower surface is covered with fine short hairs
The upper stems terminate in several flowerheads. Each flowerhead spans 2–3½" across, consisting of 10-20 yellow ray florets and numerous yellow disk florets (typically about 60). The disk florets are fertile, while the ray florets are sterile. Individual ray florets are oblong in shape and petal-like, while the tiny disk florets are tubular-shaped with 5 spreading lobes. At the base of each flowerhead, there are several floral bracts (phyllaries) that are light green, linear in shape, and ciliate along their margins. They are arranged loosely together. The blooming period occurs from late summer into the fall and lasts about 1½ months. Each fertilized floret is replaced with an achene about 3-4 mm. long that is oblongoid in shape and somewhat flattened; there are 2 deciduous awns at its apex. The root system is fibrous and rhizomatous. This sunflower often forms vegetative clumps.
Cultivation: The preference is full to partial sun, moist conditions, and soil containing loam, sandy loam, or muck. The size of individual plants varies according to soil fertility and moisture levels.
Range & Habitat: The native Luxuriant Sunflower is found primarily in NE Illinois, where it is uncommon (see Distribution Map). Because this sunflower is a hybrid of Helianthus giganteus and Helianthus grosseserratus, it is usually found where the ranges of these two species intersect. Habitats include sedge meadows, calcareous fens, edges of sandy and non-sandy marshes, and moist prairies. This sunflower is found primarily in moist open areas.
Faunal Associations: The florets are cross-pollinated primarily by bees, including bumblebees, honeybees, and Andrenid bees. The following Andrenid bees are specialist pollinators of Helianthus spp. (Sunflowers): Andrena accepta, Andrena aliciae, and Andrena helianthi. Other insect pollinators include butterflies, bee flies, and the larger Syrphid flies. Many insects are known to feed on various parts of sunflowers, including aphids, leafhoppers, grasshoppers, leaf beetles, weevils, plant bugs, and others. Several of these species are listed in the Insect Table (excluding moths). Sunflowers are the preferred food plants for the larvae of two butterflies, Chlosyne nycteis (Silvery Checkerspot) and Chlosyne gorgone (Gorgone Checkerspot). The larvae of several moth species also feed on sunflowers (see the Moth Table). Among vertebrate animals, sparrows, goldfinches, and other birds eat the large and nutritious seeds (see the Bird Table), as do some small rodents (Thirteen-Lined Ground Squirrel, Meadow Vole, and White-Footed Mouse). White-Tailed Deer and the Cottontail Rabbit feed on the leaves and young stalks of sunflowers. Among wetland species, the Muskrat occasionally feeds on the stalks or uses them in the construction of its lodges. In general, the ecological value of this and other sunflowers to wildlife is high.
Photographic Location: A prairie at Meadowbrook Park in Urbana, Illinois, where this species was introduced.
Comments: This sunflower is usually taller than the surrounding vegetation and quite showy. Luxuriant Sunflower is similar in appearance to its parental species, Helianthus giganteus (Giant Sunflower) and Helianthus grosseserratus (Sawtooth Sunflower). This hybrid sunflower and its two parents can be distinguished from each other by examining their respective stems: Giant Sunflower has stems that are abundantly covered with long spreading hairs, while Sawtooth Sunflower has stems that are hairless and often glaucous. The Luxuriant Sunflower is intermediate between these two: its stems are sparsely covered with short bristly hairs. However, some authorities prefer to classify specimens with such stems as variants of the Giant Sunflower. All three of these sunflowers prefer open habitats that are somewhat damp. Such sunflowers rank among the preferred hosts of an uncommon parasitic plant, Cuscuta glomerata (Rope Dodder). Because of its dense mass of flowers, this is one of the more attractive Dodder species.