Invasive of the Week: Creeping bellflower (Campanula rapunculoides)

By Katie Stannard

We wanted to share a changing of the guard: Emily Lilla (invasives guru, founder of this series and all-around terrific natural areas technician) is off to grad school with our best wishes and gratitude for her work at Matthaei-Nichols. Katie Stannard of visitor services is continuing Emily’s informative series with this post, resuming its regular schedule next week on Instagram and Facebook.

Like you, our staff grapple with invasives in their home gardens. Children’s garden manager Lee Smith Bravender sought advice from staff on identifying and eliminating creeping bellflower: “I have been physically digging this thing for years; clearly I’m propagating it. I spent my morning in the rain, again trying to dig it all up and nearly exhausting my supply of strong language.”

Native to Europe and western Asia, creeping bellflower (also known as rampion bellflower, rover bellflower, European bellflower) is listed as a noxious weed. It presents as a durable perennial, growing in moist soil but adaptable, taking root in cracks, and in dry, shady or sunny areas. Heart shaped leaves emerge in early spring, followed by 2-4 foot stems with alternating, spear-shaped, serrated leaves. Light purple bell-shaped flowers appear along the stalk’s upper end. Though a single plant can produce thousands of seeds, its root system seems nearly invincible.

In response to Smith Bravender’s question, curator David Michener shared these insights on the plant’s ecology, and strategies for trying to eliminate it: “Campanula rapunculoides have storage roots/stolons beyond the slender roots that come out when pulled. Those horizontal stolons swell and then deploy dactaloid (finger-like) storage roots vertically down into the soil. These have no stems and leaves anywhere near them–but they will vigorously re-grow stolons and at some distance send up new photosynthetic stems (and flowering stalks).

This “hiding” ecological strategy allows part of the clone to be found/eaten/destroyed, but the clone as a colony is quick to re-colonize on a fertile site.

I have managed to purge the garden of it by:

1. Removing it by digging.
2. I’ll trace the slender runners to where they won’t budge and dig out the general area, sifting out for any fragments of the fleshy roots.
3. Any/every fragment regrows, so those I destroy on emergence–repeatedly–to carbon-starve-deplete the storage reserve.
4. Persistence is what does it–but dig down the better part of 9″ once you’ve cleared the area (again) to get all the lurking fragments.
5. Once it’s into sidewalk cracks, this is one of the few situations where I’ll carefully use an herbicide. Otherwise the struggle can go on for years, and plants with storage roots are notorious for skipping a year. After all, the storage cells are alive, barely metabolizing, and only need to reconfigure a meristem. No rush on that front.”

Other avenues for trying to mitigate creeping bellflower include smothering, by covering patches with newspaper or cardboard then piling with soil or mulch. Some also suggest solarizing: covering with black plastic (such as a black garbage bag held in place with rocks or soil).

#matthaeinichols #umichnature #umich #invasiveoftheweek

Cover photo credit: John Ruter, University of Georgia, Bugwood.org

Sources:
Midwest Invasive Species Information Network (MISIN)
Missouri Botanical Garden Plant Finder