Sweet Autumn Clematis: Beautiful and Invasive
Star-shaped flowers burst forth in late summer, but their smothering vines overwhelm native plants.
By Kim Gaffett, OVF Naturalist/TNC
If you are going about your day on Block Island in early September, you cannot help but notice large, billowy-white snowdrifts of flowers. Look closely and you will see not one, but thousands of small star-like flowers massed together on a matrix of sturdy vines.
When I first noticed sweet autumn clematis (Clematis ternifolia) years ago, I thought of it as a real beauty. The flowers, in their form and glowing whiteness, seemed to almost sparkle. They present themselves, almost like clockwork, during the last week of August and around Labor Day. In many years—not this year where the grass and landscape have stayed green—they appear to be especially beautiful and welcome against the sun-scorched fields and trails of a long, hot, dry summer.
A Parade of Summer Flowers
Like many of us, I mark the passing of summer by its parade of flowers. June is full of roses: beach, multiflora, Carolina, all lovely and fragrant. July brings along black-eyed Susans, ragged sailors (chicory) and Queen Anne’s lace. And then, before you know it, you see rose-of-Sharon budding and blooming, a sure sign that July is giving way to August. Showy bright flowers like turk’s-cap lily and strange and discrete flowers like ghost pipe and ladies-tresses usher us through early August. Late August brings us more subtle native plant blossoms: boneset, Joe-pye weed and sea lavender. These beauties will last into September, and then the great profusion of goldenrods will plate the island during the last days of summer into fall.
Harbinger of Changing Seasons
Twenty years ago, when I first started noticing sweet autumn clematis around the edges of the Ocean View Pavilion fields in the last week of August, I would sigh with relief and wonder. Oh, how did we get to the end of summer so fast? I would take in their brilliance and sweet-smelling bouquet and think, with a tinge of sadness and a flush of anticipation, summer is nearing its end, and clematis is ushering in fall.
I still feel a mix of emotions and wonder when I see the first bursts of sweet autumn clematis. But now my observation is tempered by noticing how the plant has proliferated. This week (mid-September) I seem to see it everywhere. I see it enveloping shrubs and hedgerows, popping up out of the top of neatly trimmed hedges, spiraling up a tall spruce tree and overlaying budding sprays of goldenrod as if it were a seine net trying to gather and hold the goldenrod in place.
Invasive But Not All Bad
The truth is sweet autumn clematis, as beautiful as it is, is an aggressive, non-native, invasive species. It is in the buttercup family and is toxic to most mammals, including humans, and thus deer resistant. The flowers produce feathery seeds that can fly far and wide, which has contributed to the distribution of this species all over the island. However, this invasive plant does provide late-season nectar for hummingbirds and pollinator insects. And because of the thick tangle that the vine forms, it can provide shelter and habitat for small animals, including birds.
Beauty is in the eye of the beholder, and nothing (and no one) is all bad or all good. I will continue to see the beauty of sweet autumn clematis, when it suddenly arrives on the scene in late August, as a starry beauty and welcome harbinger of autumn. But I’m going to hack it out of my spruce tree and try to keep it at bay where it threatens other species and landscapes. At least it doesn’t have thorns.
Author’s note: There is a native clematis, virgin’s bower (Clematis virginiana), also known as devil’s darning needle. This species is much less aggressive and is often used in garden settings. If anyone on Block Island has virgin’s bower on their property or in their gardens, I would love the opportunity to take some photos to see how the plants compare.
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