Today’s subject is a bit unseasonable, since the plant I’m discussing doesn’t bloom until the shortening days of early autumn. But like most of our native vegetation, it’s breaking dormancy as you read this. And as the gardeners among you contemplate your spring planting campaigns, this column may serve as a timely recommendation for a plant that is beautiful, easy to grow, and beloved by pollinators of all kinds.
I’m talking about seaside goldenrod, Solidago sempervirens. The scientific name says it all; “sempervirens” means “always living,” or a bit more loosely translated, “indestructible.” Adapted for the harshest conditions our region has to offer — coastal sand dunes, with relentless sun, lean and droughty soil, and frequent dousings of salt water — this stuff is nearly impossible to kill.
Much of the secret of this plant’s hardiness lies in its leaves, which are thick, fleshy, and covered in a robust, waxy cuticle. It’s a configuration that stores water readily and steadfastly refuses to surrender it to evaporation; faced with relentless sun and a drought, Solidago sempervirens simply slows down a bit and lives off its stored resources. The thick cuticle has the added effect of preventing the absorption of salt from ocean spray or overwash; seaside goldenrod lives happily in conditions that would kill a lesser plant.
Seaside goldenrod first came to my attention as a favored nectar source of migrating monarch butterflies. The southbound migration of this popular butterfly in our region is largely coastal, perhaps simply because the southwesterly trend of the coastline intercepts the southerly travel of these butterflies, which then opt to follow the shoreline southwest rather than continue southward over open water.
The period of peak monarch movement coincides with the bloom period of this goldenrod, and since few other nectar sources are available along the immediate coast, the butterflies rely extensively on seaside goldenrod blossoms. While the number of migrant monarchs transiting the Vineyard has declined steadily in recent decades, a good clump of seaside goldenrod remains a reliable place to find this insect.
But the appeal of these flowers extends far beyond butterflies, and must result from more than just overlap in time and space. Bees, wasps, flies, and beetles visit seaside goldenrod in huge numbers, clearly preferring this plant to any other nectar source. Nobody seems to know exactly what the attraction is. But presumably, the nectar and pollen this plant offers are especially nutritious, and perhaps especially easy to access, making seaside goldenrod flowers a wildly popular resource.
Most strikingly, an entire suite of native bees focuses its adult activity around this plant. Multiple species in the genera Colletes and Andrena are pollen specialists on goldenrod, rarely visiting anything else as they forage, and given a choice, most of these bees unfailingly choose sempervirens over any other Solidago. Many generalist bees, such as the ubiquitous common Eastern bumblebee, Bombus impatiens, also freely visit this flower. So a prime patch of Solidago sempervirens can be alive with pollinators during the plant’s September and early October bloom period.
Seaside goldenrod is grown quite widely as an ornamental, which is not surprising given its toughness and beauty, and several named cultivars have been developed. While it does not seem particularly popular locally as an ornamental, a quick Web search shows many regional nurseries carry this plant, including some on Cape Cod and a few that purport to offer Vineyard-origin stock. So suitable material should be readily available to anyone wanting to add flashy gold flowers and a prodigious pollen and nectar source to a yard or garden. Plant a bunch of them, that’s my advice!
Despite its optimization for life on coastal dunes, this plant is highly adaptable. Even in the wild, its occupancy often extends into the wetter, heavier soils of salt marsh margins. And in cultivation, Solidago sempervirens grows like crazy when given the even moderately friendly conditions of a not-too-badly neglected garden. It does not, however, show much inclination to spread by rhizomes, or even to seed itself in; while the plants in my yard are massive, they have shown no alarming tendency toward excess zeal.
Off-Island, the natural range of this plant extends from the Gulf of Mexico east and north to the Maritime Provinces. Away from its native, coastal range, it must be said, the vigor of seaside goldenrod can be problematic; in at least one midwestern state, Wisconsin, this species is legally restricted as potentially invasive.
While some sources suggest that seaside goldenrod tends to live less long than other goldenrods, my own experience is to the contrary. Some plants in my yard are 25 years old, and show no sign of fading. About the only problem this species seems susceptible to is a leaf rust of some kind, starting on the lower leaves and climbing as the plant senesces, but this affliction seems to have no effect on either blooming or survival.
I eagerly await September, when I can stake out seaside goldenrod patches for insect photography. But in the meantime, consider installing a few plugs of this species in your yard; your local pollinators will be delighted.
