Description: This native perennial plant is 2-3½' tall. Sometimes it is slender and little branched, while at other times it branches frequently, creating a bushy appearance. The slender stems usually have lines of fine white hairs. The alternate leaves are linear and have smooth margins. The larger leaves have 3 conspicuous veins, although the smaller ones usually have only a single conspicuous vein. They are up to 4" long and 3/8" across, or slightly wider. Sometimes there are a few white hairs near the base of the leaves and along the central vein on the underside. There are clusters of small composite flowers at the apex of the plant and many of the upper side stems. These flower clusters are usually rather flat-headed, but they sometimes assume a round-headed appearance. Each composite flower is yellow, consisting of about 21-35 disk florets and ray florets (when considered together). It is only about 1/8" across – smaller than the composite flowers of other goldenrods. These compound flowers often bloom gradually, rather than simultaneously, with older flowers turning brown while younger flowers are still in the bud stage. The blooming period is late summer to early fall, and lasts about 1 month. Sometimes there is a mild floral scent. The root system is fibrous, and new plants develop vegetatively from rhizomes. Overall, Grass-Leaved Goldenrod is rather variable across different localities.

Cultivation: The preference is full sun and moist conditions. However, this plant tolerates drier conditions, and can be surprisingly drought tolerant. The soil should contain high amounts of organic matter; some varieties of this plant also grow in moist sandy soil. Powdery mildew seems to bother this goldenrod less often than many others. It is easy to grow, but can spread aggressively in moist sunny places.

Range & Habitat: Grass-Leaved Goldenrod occurs occasionally in most counties of Illinois. However, it can be locally common in some wetlands areas. Habitats include moist black soil prairies, edges of marshes, sandy pannes between dunes, calcareous seeps, borders of lakes, abandoned fields, and ditches along railroads. Grass-Leaved Goldenrod occasionally occurs in drier habitats, but it has greater trouble competing with other forbs, such as Solidago canadensis (Canada Goldenrod), in such places.

Faunal Associations: The small flowers attract many kinds of insects, including long-tongued bees, short-tongued bees, wasps, flies, butterflies, moths, and beetles. Various wasps and a few beetle species, such as Chauliognathus pennsylvanicus (Goldenrod Soldier Beetle) and Epicauta pensylvanica (Black Blister Beetle), seem to be especially attracted to the flowers. The caterpillars of several species of moths eat various parts of this and other goldenrods. The seeds are eaten by the Eastern Goldfinch and Swamp Sparrow to a limited extent, while the foliage is occasionally consumed in limited amounts by the Greater Prairie Chicken, Cottontail Rabbit, and White-Tailed Deer.

Comments: Grass-Leaved Goldenrod has more slender leaves than other goldenrods in Illinois, except for Euthamia gymnospermoides (Plains Grass-Leaved Goldenrod). However, there is only a single conspicuous vein in the largest leaves of this latter species, the stems are hairless, and it has only 12-20 disk and ray florets in a compound flower (when considered together). Many of the leaves in the upper photograph are from neighboring plants of Solidago canadensis (Canada Goldenrod), while the black spots on the flowers are tiny beetles.