Horticultural Morality

In late August, when the heat and humidity in my Mid Atlantic Zone 7 neighborhood have done in most of summer’s beauties, I’m on the look out for plants just coming into their own — like the sweet-scented, white flowers of a clematis vine popping up all over the alley fences in the neighborhood. When the volunteer vine first emerged on my fence, I could tell it was a clematis; the distinctive woody stem and swollen nodes made this volunteer stand out from the bind weed, Virginia creeper, and porcelain berry vines fighting for a hold on the fence. So I let this one grow to see what would bloom. It turned out to be Clematis terniflora, or Sweet Autumn Clematis, which is an accurate, if boring, descriptive name.

C. terniflora decorating Christmas tree

C. terniflora decorating Christmas tree

clematis kills tree

C. terniflora smothers a pine tree

Sadly, it is also a non-native, invasive species in my area. It indiscriminately casts its feathery seeds, which are carried long distances by the wind. The vigorous vine quickly overtakes other plants, each seedling growing 15 to 30 feet, forming a dense blanket, blocking sunlight and smothering the plant below. My tax dollars are working hard to remove it from the local national parks. That is enough reason for me to remove the plant.

I strolled around the neighborhood and found it growing in every yard on my block, and most others in a two-block radius. It wrapped around evergreens like Christmas lights, and smothered shrubs, trees and detached garages. All of the photos in this post were taken in one alley. So, although I like the plant, I’m yanking it in what is sure to become an annual Sisyphean task (especially because the local garden centers are still selling this volunteer weed — for $12.99 no less!)

As with most invasive plants, however, I could replace it with a similar native cousin — Clematis virginiana, colorfully known as Virgin’s Bower, Devil’s Darning Needles, or Old Man’s Beard. Notably, the local garden centers do not sell this native.

Common plant names are often applied indiscriminately, so it is important to know the difference between the native and invasive varieties in your location, no matter what your neighbor or grandma calls it. You can tell C. terniflora from C. virginiana by the leaves. Both are semi-evergreen vines with compound, opposite leaves, but C. terniflora has 3-5 leaflets that are ovate or broadly lanceolate to narrowly dentate, non-toothed or entire, glossy, and stiff. C. virginiana has three, toothed or lobed leaflets of standard leaf thickness.

C. terniflora has smooth leaf margins

C. terniflora has smooth leaf margins

USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.

C. virginiana has toothed margins.
USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species.

Both plants have white flowers that look and smell quite similar, and seed pods that look like, well, the devil’s darning needles. Later as the seeds are ready to take flight, they become feathery, like an old man’s beard. And while the virgin is also fertile and vigorous, it does not similarly threaten the purity of local flora. To me that makes her the morally superior choice for my locality.

 

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