Goldenrods: Food for pollinators in fall
One of the autumn delights in Western Pennsylvania is the appearance of goldenrods (Solidago), whose bright golden inflorescence plumes grow in masse along roadsides, abandoned fields and meadows.
Goldenrods are members of the Asteracae family, which includes fall perennials such as asters and daisies. Solidago has 138 species worldwide, with 115 species native to Canada and the United States.
Goldenrods are perennial plants that often produce vertical woody shoots from horizontal rhizomatous stems, allowing the plants to spread quickly over favorable areas. Thus, the field of goldenrods along the highway may be one large, genetically identical clone. In addition to rhizome production, goldenrods reproduce by seed.
The beautiful yellow color of goldenrod blooms attracts a variety of pollinators, including insects, native and honey bees. Insects use their complex eyes to find the colored flowers that will give them a meal of pollen, transferring the pollen as they travel from flower to flower.
Goldenrods are one of the last blooming fall perennials and therefore are an important food source for pollinators, making goldenrod an attractive option for the fall garden landscape.
While wild goldenrod plants can be aggressive in the home garden, there are many goldenrod cultivars that do not overtake the garden space. For example, solidago nemoralis does not reproduce by rhizomes and generally grows where it is planted.
Like many native species, goldenrods are not fussy and require little maintenance.
Plant goldenrod in full to part sun and offer a light fertilizer in the spring. Cut them back in early summer to keep them from flopping over later in the season. Plant goldenrod anywhere in the garden to provide a pop of bright yellow in the fall and green foliage in the spring and summer.
Gardeners may notice spherical growths, about the size of a golf ball, on many of the stems of goldenrods.These growths are noticeable on the previous year's dead stems during the winter months. These growths, or galls, usually are caused by the goldenrod gall fly eurosta solidagnis. The female lays her eggs on the goldenrod stem in the spring. The eggs hatch and the larvae spend the summer feeding inside the goldenrod stem.In response to chemicals released by the larvae, the goldenrod forms the gall, where the larvae stay protected from the winter weather. In the spring, the larvae pupate, bore a hole through the wall of the gall, and emerge to start the cycle again.The process does not seem to have a detrimental effect on the goldenrods. The larvae themselves serve as a food source for other species. Two species of Eurytoma wasps inject their eggs into the gall and their larvae will feed on the Eurosta larvae and emerge from the gall in the spring instead of the fly. Downy woodpeckers and black-capped chickadees break into the gall to feed on the larvae as well.People with fall allergies often blame the goldenrods for their symptoms, but the true culprit for these seasonal symptoms is ragweed (ambrosia). The goldenrod's yellow blooms have heavy, sticky pollen, which attracts pollinators. Their pollen is too large to float in the air and cause allergic reactions.Ragweed's greenish, inconspicuous flowers have tiny pollen grains; ragweed depends on the wind for pollination. These pollen grains are inhaled into the lungs, causing allergic reactions. Both perennials grow in the same meadows, and fields bloom at about the same time.Goldenrods can be a lovely addition to your native garden, putting on a fall show after most perennials have faded from the landscape. With no potential for allergic reactions to their pollen, explore the varieties of goldenrod suited for the home garden.For more information on goldenrods, go to https://extension.psu.edu/programs/master-gardener/counties/northampton/news/2018/goldenrods-and-asters-great-pollinator-plants-for-the-fall.Carol Chmielewski, MSc, is a Penn State Extension Butler County Master Gardener.
