Goldenrod: Not Just Another Pretty Face

Goldenrod, a member of Asteraceae, blooms in late summer through early fall and is often found in dry open areas and along roadsides. While often dismissed as simply a weed, this showy native North American perennial, genus Solidago, has a lot to offer. Creating a profusion of yellow, hundreds of 1/8 to 1/4-inch-wide individual flowers bloom together to create wand-like clusters on arching branches. Its botanical name, Solidago, is Latin for solidus, meaning "to make whole." This refers to the plant's healing and medicinal properties. It has been used to heal wounds of the skin and to treat inflammation of the mouth and throat, tuberculosis, diabetes, and arthritis. It has diuretic and anti-inflammatory properties. Native Americans have used its leaves as a poultice for bee stings and have made tea with its flowers and leaves to reduce fever. During the American Revolution, goldenrod tea was made as a substitute for British tea.

A prolific nectar and pollen producer, it supports bees, wasps, butterflies, moths, and beetles. Eleven species of native bees are specialists in goldenrod and seek this specifically for their diet. It is also the host plant for several butterfly and moth larvae, including the wavy-lined emerald moth (Synchlora aerata). Goldenrod is often blamed for seasonal allergies. However, its pollen grains are large, sticky, and dense. They are too heavy to be carried by wind and are carried by insects. This is quite different from ragweed, which blooms at the same time. Ragweed is wind pollinated, and one plant may produce a billion grains of pollen. This lightweight pollen may remain airborne for several days and can wreak havoc with seasonal allergy sufferers. Goldenrod produces high-quality pollen, rich in protein, fats, and minerals, and is critical for migratory insects like the monarch butterfly.

While goldenrod supports a wide variety of insects that forage on it while blooming, it also supports a variety of other animals throughout the year. Golf-ball-shaped swellings called galls are commonly found on goldenrod stems. Goldenrod is host to around 50 species of insects, including flies, moths, and midges, that cause this overgrowth of plant tissue. One common insect is the goldenrod gall fly (Eurosta solidagnis), a tephritid fly smaller than the housefly with translucent wings mottled with brown splotches. This clumsy flier only lives 10 to 14 days and completes its entire life cycle on goldenrod. Each species of fly is specific to a specific species of goldenrod. Female flies detect the correct species by using chemical sensors on their feet and antenna to taste the goldenrod as they walk over its buds. After mating in early spring, the female deposits her eggs in the goldenrod stem. Once hatched, the larvae begin feeding inside the stem. The saliva of the larvae is thought to contain a chemical that mimics plant hormones and causes the plant to grow abnormally, forming the gall. The exterior of the gall is hard and cork-like, while the interior has the consistency of damp wood. As the larvae grow through a series of stages called instars, they eat the interior of the gall, forming a chamber. By fall, at the last instar, they tunnel almost to the outside of the gall's surface, leaving just a thin layer of plant tissue. They will enter an unanimated state called diapause and spend the winter inside the gall. In early spring, they pupate and, by mid-spring, emerge as adult flies. Since adult flies do not have chewing mouthparts, they inflate balloon-like structures between their eyes to push their way out of the thin outer layer of the gall.

Two types of moths that cause galls to form are the goldenrod elliptical-gall moth (Gelechia gallaesolidaginis) and the goldenrod gall moth (Epiblema scudderiana). Goldenrod elliptical-gall moths are specific to two species of goldenrod, tall goldenrod (Solidago altissima) and giant goldenrod (Solidago gigantea). In the fall, the female moth lays her eggs on goldenrod leaves or in leaf litter around the plants. The eggs stay dormant through the winter and hatch in the spring. The larvae burrow into the goldenrod stem, where its presence causes the plant to produce the gall, which in turn provides food for the larvae. The larvae pupate inside the gall and emerge in early fall to mate and lay eggs. The goldenrod gall moth has a slightly different life cycle. Mature larvae overwinter in the gall and pupate in the spring, emerging as adult moths by mid-spring. Before winter, they excavate exit tunnels leaving only a thin layer of plant tissue, and spin silken funnels to guide them into the exit in the spring.

Gall fly larvae provide food for other animals. Two species of parasitoid wasps lay their eggs inside the galls. When the larvae hatch, they feed on the fly larvae. Birds like downy woodpeckers and black-capped chickadees also eat fly larvae. These birds break open the galls and eat the larvae inside. Goldfinches, grosbeaks, and nuthatches eat goldenrod seeds.

With more than 120 species and numerous cultivars of goldenrod, it is easy to find the right plant for your space. Goldenrod can spread aggressively, but some ornamental varieties don't spread as quickly. There is also a wide range of sizes, as some grow over six feet, like tall goldenrod, and some only around two feet, like blue-stemmed goldenrod (Solidago caesia). Supporting so much life, goldenrod could be a great addition to your garden and worth more than its weight in gold.