As interest in native plants grows, gardeners and environmentalists attempt to rehabilitate the image of goldenrod, wildflowers of the genus Solidago in the Asteraceae family. Foundational to local food webs, in fact, goldenrods are arguably the most environmentally beneficial herbaceous plants that we can propagate in yards and public spaces in Harvard.
To find out more about how to use goldenrod to enhance ecological functions—and add color to the garden—I interviewed Adam Kohl, a naturalist based in Wendell. In addition to his work conducting ecological field studies, Kohl also works as conservation agent for the town of Wendell and operates a native plant nursery in which he grows a variety of goldenrods. I started by asking Kohl why Solidago is considered a keystone species, a linchpin in local ecosystems (according to author and professor Doug Tallamy, a renowned expert on plant-insect interactions).
Kohl explained that the relationship between butterflies and moths and Solidago has gained a fair amount of attention. (The Native Plant Finder feature on the National Wildlife Federation website—the work of Tallamy and his research assistant—lists Solidago as host to 125 species of butterflies and moths, including in the larval stage; in turn, land-based birds feed their young almost exclusively on caterpillars.) According to Kohl, Solidago also acts as a host to leaf-mining flies and 11 specialist bees—across four genera—that collect pollen from Solidago with which to provision their nests.
“There was one night when my kids and I went out [with a headlamp] and we counted over 100 moths in less than a few minutes visiting the flowers of Solidago rugosa. Goldenrods are very accessible for nocturnal pollination. They are like giant landing pads with tons of flowers, moths just hang out there and nectar.”
Galls on goldenrod plants offer evidence of the plant’s close relationship with insects: These commonly observed growths of plant tissue are produced by flies or moths that require Solidago for their life cycle, Kohl explained. New discoveries about such relationships continue to emerge. For instance, Kohl said some Solidago species have evergreen basal foliage. “There’s a micromoth (Bucculatrix sp., likely B. staintonella) that mines these evergreen leaves as larvae throughout the winter. This is a discovery that appears new to science, and I’m working on rearing the larvae to confirm the moth with Charley Eiseman, but it looks like at least a new host plant record.”
Given the grave concern over insect decline raised in multiple academic and popular journals in recent years (including a January 2021 symposium at the National Academy of Sciences), Kohl’s observations should encourage all of us to plant more goldenrod. The late summer beauty, however, has an image problem, Kohl notes: “Often people are turned off instantly when you try to sell them a goldenrod. The first concern is allergies, and you have to let people know that’s just a myth, they don’t cause allergies. In fact, they can protect against allergies by consumption of the healthful flowers as tea,” (which Kohl also enjoys). Many people associate goldenrod with aggressive growth patterns. Kohl says to help people appreciate goldenrods, he tries to explain the range of species, and how goldenrods are diverse and varied.
Catherine Warner is an enthusiastic amateur gardener who got started by following her dad around the garden and later worked on an organic farm while in college. After a detour as an academic historian, she now stays at home with her son and serves as a member of both the Garden Club of Harvard and the Community Resiliency Working Group.
Adam Kohl’s tips for planting Solidago
1
Before planting more goldenrod, take stock of what is already growing in your yard. Learning to identify goldenrods can tell you a lot about your site and what’s going on there. There are 25 species in New England, and there’s basically a goldenrod for every occasion, for every habitat type, from dunes to rich woodlands, bogs to sandplains.
2
If you want to help out specialist—as well as generalist— insects, select different species of Solidago to extend bloom time. S. juncea (early goldenrod) blooms in early July. The last ones I observe blooming, into late October, are S. sempervirens (seaside) and S. caesia (bluestem). It’s best to have at least three species to stretch out your bloom time and to get your Solidago in the ground by early summer—they grow most rapidly in the hot months before blooming. S. odora, the licorice goldenrod, blooms on the earlier side and measures about 3½ feet tall—its flowers and leaves make an herbal tea which tastes like anise.
3
Understanding where and how a plant typically grows can help you find the right one for your site. S. sempervirens is good for areas that get hit with road salt or road sand—its native habitat is the dunes in coastal areas. You will also find it spread across the highway medians outside its native range because it’s so salt- and drought-tolerant. S. nemoralis (measuring approximately 2 feet tall) is great for harsh, dry, I’ll-never-water-this-again situations. Two (nonaggressive) shade species, S. caesia and S. flexicaulis, are under 3 feet and very graceful in a shade garden.
4
All goldenrods do not elbow out their competitors, but some have a stronger spreading habit which can, nevertheless, be managed effectively. Most people associate Solidago with Canada goldenrod—it has the reputation of being the most monocultural. If you are looking out at a sea of head-high goldenrod in your field, you can add larger shrubs like elderberry or willow to diversify your landscape. Plant over it rather than under it.
5
An easy way to grow Solidago is to identify and encourage the dispersal of seeds from the plants already growing on your site. Shake the seed heads when seeds are starting to blow in the wind. All seeds need good seed-to-soil contact to germinate. The seeds are small, and if covered with soil too deeply might not germinate; just a very light covering is best. However, if planting in existing garden beds, gardeners will typically find it convenient to use plugs or nursery stock.
With these guidelines in mind, find your Solidago species (or three!), and enjoy observing the happy insects you will attract.
