Of all the invasive plants we removed in our own landscape, Creeping Bellflower (Campanula rapunculoides) was by far the worst to eradicate. This pernicious perennial, native to Eurasia is very common in the midwest, growing out of cracks in urban sidewalks, creeping along alleyways, and in the suburbs forming large clusters in partially shaded woodlands and woodland edges. A common plant that unknowing gardeners trade or give away to others “because they have so much of it”.
Creeping Bellflower is not easy to eradicate because it has extensive tap roots and thread like shoots that arise from the taproot. These threads weave their way through the soil horizontally emerging at the soil surface and produce a tidy cluster of heart-shaped basal leaves.
In a site with soils that aren’t compacted, tap roots can be as much as 2 feet below the soil surface. I had Creeping Bellflower interspersed with my native violets and the leaves are so similar that I would often wait for the flowers to emerge to mark it.
Creeping Bellflower flower. Opens in July.
HOW TO ERADICATE CREEPING BELLFLOWER
The two methods I used were smothering the plants with heavy paper and wood mulch in areas where the soil was drier and the plants were more sparsely spaced. This essentially killed off many of the various clusters of plants that were growing from a small thread. Within two years, clusters that reemerged through the paper were almost all right above the taproot. This then made it easy to carefully dig the taproot out and all of the small ‘threads’. If you leave any part of the taproot or threads then you will have a new cluster of leaves regrow within a couple of months.
The other method was simply a lot of digging. On the south side of our house where the Bellflower was interspersed with natives, I worked for 3 years digging out all taproots and threads, following the fine threads deeper into the soil until I found the taproot. I would go through the area digging in the spring. Whatever I missed would reemerge in the fall, the soil in many of these spots loosened from the digging made it easier to pull out the offending piece of root system. Once satisfied I had removed 95% of the Creeping Bellflower, we then were able to start work on planting in this area to restore it. It would have been a huge mistake to plant here before the Creeping Bellflower was eradicated as it interweaves with plants, and seems to love newly disturbed loose soil to spread into.
Note: Treating Creeping Bellflower with herbicides is ineffective because of the reserves that are stored in the taproot. It may kill off a few clusters but new ones will reemerge.
A WONDERFUL NATIVE ALTERNATIVE
Growing out of rocks by Lake Superior shore
There are several native Campanula, the one most widely distributed in North America is Harebell (Campanula rotundifolia). One of my favorite natives, this delicate thin leaved perennial is tolerant of dry, harsh sites.
Growing out of the cracks in the rock outcroppings on the south side of Lake Superior, to high altitudes in Colorado to dry prairies in the midwest this is a great candidate for tough sites. The beautiful blue cup-shaped flowers emerge in mid June in Minnesota, earlier southwards.
Hillside covered with Harebell in Colorado Image @ Al Schneider from USDA Plants Database
An ideal native to mass along a rock retaining wall in hot exposed sites or border a pathway.
The seed of Harebell is extremely small and hard to collect. The seed capsules dry,open and shake the seeds out like a salt shaker. One needs to stay on top of the capsules maturing to collect seed. Harebell seed needs light to germinate. I often collect the seed and rebroadcast right away in my yard on any bare soil.
Harebell reaches heights of about 12 inches, sometimes taller in wetter locations or seasonably wet years. Many native bees love to nectar on the flowers, I especially have seen many Slendid Metallic Green Bees on my Harebell flowers.
© 2012, Heather Holm. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us
About Heather Holm
Glad to hear there is a way to get rid of this pesky plant…I am trying to cultivate the native bellflower. I hope it grows this year…I do love the flower. Will give these methods a try…the clumps I covered with wood mulch have diminished so perhaps this year I can eradicate more.
Hopefully you’re smothering works at diminishing your population. Good luck.
Heather recently posted..Native Plant of the Week: Cucumber Vine ~ Echinocystis lobata
So Pretty! I checked and there are 3 species native to FL. One limited to the panhandle, one appears in two counties on the gulf coast and is endemic AND endangered. I was thrilled to find that the 3rd species in endemic to FL and was found in my county. I’m putting it on my list!
Loret recently posted..Responsibility on the Internet
Loret – great to know you have several native Campanulas in FL. I’m sure our southern readers will consider these, thanks.
Heather recently posted..Native Plant of the Week: Cucumber Vine ~ Echinocystis lobata
While digging is OK in gardens, it opens up the seed bank and causes new invasives that are hard to control in the wilds. Likewise, smothering is difficult in the wilds as you can’t necessarily keep the mat in place.
Have you considered repeated ground cutting the harebell, combined with gentle hand-pulling of small seedlings? Here, I’d like to see what monthly or bi-weekly cutting of the tap root just below ground level would do. The biggest issue, of course, would be the volunteers’ feet. You’d need work trails, stepping stones etc so they don’t end up compacting the soil and trampling all the good plants.
I totally agree regarding digging Sue, less disturbance the better. The main problem is the depth of the taproots, as deep as 2 feet which will create disturbance with your proposed method regardless. I would suggest selective smothering first, then waiting. This will minimize the amount of digging. After removing taproots, mulch disturbed soil well with wood mulch then leaf litter to discourage weed seed germination. In large areas, with enough help, I would dig the natives out, relocate nearby then remove the Bellflower. They then wait a year or two ensuring eradication, then replant. It’s not a great process any way you go about it unfortunately. It’s one of the reasons I wanted to highlight this plant as it’s so problematic to get rid of.
Heather recently posted..Native Plant of the Week: Cucumber Vine ~ Echinocystis lobata
how widespread is harebell in the wild in your area? in what of cultural conditions?
oh, I see the posts says part-shade, woodland. small clusters or whole fields?
reason I ask is that what you propose for restoration is drastic. I have had very good results with many herbaceous perennials by ground cutting – but you have to do it every 2 to 4 weeks for the whole growing season (say May 1 to Oct 1) sometimes for 2 or 3 years.
As far as I know we don’t have this invasive in my area Georgia. I am very fond however of the native Campanula divaricata that we have. Can you recognize this one by it’s milky sap when you tear a leaf? That could help you distinguish it from violets.
Ellen Honeycutt recently posted..Taking Stock of the Flock
No, as far as I know it doesn’t have milky sap. Wouldn’t that be nice to help distinguish it. I’m not familiar with the divaricata, I’m going to look it up right now, thanks.
Heather recently posted..Native Plant of the Week: Mayapple ~ Podophyllum peltatum
Hooorrraaayyy! Finally a non-native invasive that I am not currently fighting.
LOL. Yes and count yourself lucky that you don’t have this one!
Heather recently posted..Propagating Remnant Populations of Rattlesnake Master