As summer winds down, the gold rays of summer are converted into the showy blooms of the many species of goldenrod that flower from late summer to fall. While many species of wildflowers may continue to flower into the fall, goldenrods dominate the fall wildflower scene. In fact, goldenrods are so prevalent in the fall that they are incorrectly blamed for causing allergies. Ragweed (Ambrosia sp.) unfortunately blooms during this same period and produces the wind-borne pollen that contributes to many people’s allergies. Ragweed, with its greenish flowers, grows unnoticed along roadsides and old fields, while the goldenrods develop into vast meadows, thick with yellow flowers. Goldenrods, however, produce a waxy pollen that is transmitted by insect, not wind, and therefore do not cause allergies.
Goldenrods, genus Solidago, are members of the Composite Family. This is the largest family of flowering plants and includes daisies, black-eyed Susan’s, and dandelions. Typically, the flower cluster, inflorescence, of composite is comprised of numerous small flowers. While an individual flower on the goldenrods may be very small, the inflorescence is usually large and impressive.
Readily recognizable as a group, goldenrods can often be difficult to identify to species level. The Herbaceous Plants of Maryland recognizes approximately 30 distinct species, as well as numerous hybrids. Though there are many species of goldenrods occurring in our area, only about seven species are common.
The common goldenrods include early goldenrod, tall goldenrod, Canada goldenrod, late goldenrod, rough-stemmed goldenrod, old field goldenrod and blue-stemmed goldenrod. The early goldenrods bloom in June and are usually finished flowering by the time the real goldenrod show begins in the fall. The remaining species listed typically begin flowering in late July and August and continue flowering into and even through October.
While the identification of these individual species may be difficult, there are some general rules-of-thumb that may aid in their identification. Old field and blue-stemmed goldenrods are considered to be the shortest of the common goldenrods in our area. Typically growing to 1-3 feet in height at flowering time. Blue-stemmed goldenrod, told by its arching bluish stem, is usually found in rich woods and clearing. Old field goldenrods have a grayish, finely hairy stem and are usually found in dry woods.
Rough-stemmed goldenrod is a considered a mid-sized goldenrod and usually grows to about 4 feet. The stem is densely hairy and the leaves are wrinkled, hairy and toothed. This species is also known as wrinkled-leaved goldenrod and is common in old field habitats.
Tall, Canada, and late goldenrods are grouped together in the “tall” category. These goldenrods are typically 4-6 feet in height and can grow even taller. Late goldenrod is told from the others by its smooth greenish stem and tall goldenrod can be told by the downy grayish stem. Canada goldenrod has a greenish stem that is densely covered with short hairs near the top. All of these plants have toothed leaves and are found in old fields and meadows.
One other plant, formerly considered a member of the Solidago genus, also joins the golden display of fall meadows. Known as the flat-topped goldenrod, has a flat inflorescence and short grass-like leaves. An interesting member of the goldenrod group, this heavily flowering species is typically found in moist open areas.
These general characteristics should allow you some level of confidence when distinguishing goldenrods on your early fall hikes. Don’t despair if specific identification is difficult, goldenrods are renowned for having inconsistent field characteristics and for their crossing breeding. Wildflower guides and keys can provide further details on specific plant characteristics if you are determined to identify a particular plant to its proper species.