This past weekend, I focused my fieldwork on one of my favorite plants: seaside goldenrod, Solidago sempervirens. The common name accurately sums up the habitat preference of this important wildflower: It’s primarily a plant of sandy, near-shore areas, dunes, and even upper beaches. And the scientific name also fits: “sempervirens” means something like “always flourishing,” and indeed this goldenrod has a long growing season, a prolonged bloom period, and a cast-iron constitution.
The main reason for seeking out this plant was to search for a particular bee, Colletes speculiferus, which is said to have a special fondness for seaside goldenrod. This bee is known on the Vineyard from a couple of records, but we’re at the northernmost limit of its range. Despite the abundance here of its favored food source, C. speculiferus is probably rare here, and I wasn’t surprised that my search was not successful.
But the process of examining hundreds of seaside goldenrod flower heads reminded me of how much I love this plant. It’s a marvel in and of itself. And as a food source for a wide range of arthropods, it may be unmatched.
First, consider the physical conditions under which this plant typically grows. Its roots are often in the pure sand of dune systems, a shifting, unstable soil type that could hardly be leaner or more prone to drying out. Given its fondness for shorelines, seaside goldenrod is frequently doused with salt spray, or even washed over by storm tides. And it spends its life in full sun, which can desiccate nearly any living thing.
But S. sempervirens has a root system robust enough to anchor the plant in unstable sand and glean every drop of rainwater that comes its way. And the leaves of this plant are remarkable: thick, almost fleshy, with a thick, impermeable skin. The plant makes the most of the meager resources available to it, and retains water and nutrients in its tissue until they are needed. Relatively few other plants can flourish under the conditions seaside goldenrod is adapted to, and few of those plants rival S. sempervirens in height. So this goldenrod is virtually immune to competition.
In addition to its unbelievable hardiness, though, seaside goldenrod is a prolific source of pollen and nectar for a wide array of insects. Most famously, it is one of the most important nectar sources for South-bound monarch butterflies. Much of the Northeastern population of this iconic butterfly follows the Atlantic coastline as it moves south toward wintering grounds in Florida. And it is largely the nectar so copiously produced by Solidago sempervirens that fuels this journey.
But as my investigations last weekend showed, it’s not just the monarch that loves this flower. As I searched the masses of goldenrod flowers along Atlantic Avenue, Katama, and at Long Point Wildlife Refuge, I appreciated how many other butterflies are fond of this flower. Sachem skippers and American coppers, both exhibiting prodigious late-season flights, were common on S. sempervirens. And I tallied more than a few painted and American ladies, red admirals, and pearl crescents.
While Colletes speculiferus was nowhere to be found, other bees were plentiful on seaside goldenrod. In particular, the aster mining bee, Andrena asteris, abounded. As fond of asters as its name suggests, this bee, which is locally abundant on the Vineyard, also happily visits a wide range of late-season composite flowers, with S. sempervirens high on its list of favorites. Colletes simulans, a close relative of the elusive C. speculiferus, was also common. Bumblebees, honeybees, and the occasional leaf-cutter bee rounded out the bee roster.
Flies were plentiful, too, using, like the bees, seaside goldenrod in preference to all other available flowers. I photographed several common lagoon flies, Eristalinus aeneus, which despite its English name is anything but common on the Vineyard, feeding on this flower. And an odd-looking hover fly I photographed on this plant turned out to be Eristalis anthophorina, or orange-spotted drone fly — as far as I can determine, the first record of this fly on Martha’s Vineyard.
The fondness of all these insects for seaside goldenrod, specifically, was evident; perhaps 80 percent of what I found was on this species alone. Partly that may be the result of timing: a relatively late-blooming species, Solidago sempervirens flowers were in prime condition at a time when most other goldenrod species were starting to fade. But even where fresh examples of other goldenrod species were plentiful, it was seaside goldenrod that hosted the lion’s share of insect numbers and variety.
I haven’t given up the search for Colletes speculiferus! But when you’re focused on a plant like seaside goldenrod, even an unsuccessful search invariably leads you to many other interesting finds. Colorful, indestructible, and above all the favorite flower of many kinds of insects, Solidago sempervirens is an enduring favorite of mine, and perhaps the most ecologically important plant of our shoreline habitat.
