116 3rd St SE
Cedar Rapids, Iowa 52401
One of the worst weeds in Iowa gardens is wild campanula (Campanula rapunculoides), also called creeping campanula. Unlike the various types of perennial and annual campanula flowers available in garden centers, this perennial weed is extremely difficult to kill. If left unchecked, it will compete with other plants for water and nutrients. In some cases, as with smaller annuals, it can squeeze them out completely.
It’s a clever plant. The leaves, like its better behaved hybridized cousins sold in garden centers, are a pretty green in a charming heart shape. The plant sends up a flower stalk with lovely lavender-blue, bell-like flowers that bloom any time from June through September. But do not be deceived. This weed is evil, pure evil.
One garden writer calls it the zombie weed because it will slowly take over a garden and nothing seems to kill it (bullets are not recommended). Wild campanula’s superpower is that it has a long, delicate network of roots that extend probably a foot or so away from the plant, so even if you dig or pull it out as best you can, the parts of the root that remain in the soil spring back to life — a zombie weed hoarde that can overrun your pretty flower bed.
Native to Europe and western Asia, wild campanula prefers light shade and moist soil, but will readily grow just about anywhere, even taking root in cracks in the concrete in full sun. It’s far easier to control in spaces that are being constantly dug up or tilled, like a vegetable garden. It’s extremely difficult to control when it gets entwined with some of our favorite perennials, like peonies or iris.
The time to deal with wild campanula is now, in spring, before it flowers. Gird yourself for battle on all fronts because once it takes hold in your garden, you’ll probably have to employ all these various methods for weed control.
Absolutely the most important thing is to not let this weed flower. A single flower produces thousands of seeds that travel easily, so that wild campanula can spread readily through your yard and into your neighbors’ yards as well. Any flower stalks, which grow 1 to 2 feet high, should immediately be yanked out.
Pulling — better yet, digging up — the small plants you spot in spring helps slow down this plant. Doing this when the soil is moist is ideal. Regardless, the plants will likely come back, and you’ll need to pull them again. But depriving the roots of life-giving foliage above ground prevents the plant from spreading so much.
If you are able, dig up the entire area infected with this weed. As you work, pick out any and all foliage and roots that you can see. Be sure to just turn over the soil — don’t spread it in other areas of your garden. Then mulch the area heavily. Pull or dig up any plants that crop up later in the season. Repeat next year if you can.
Suffocating wild campanula is fairly effective. If the weeds are too tall to mulch over, first pull them out or just cut them down. Then blanket with the heaviest mulch you can — old carpet, newspaper, cardboard, landscape fabric. If you can, also top with a good 2 or 3 inches of other mulch, such as shredded bark. More wild campanula may crop up around the edges of the mulch, but at least you’ve significantly reduced the colony. You can deal with the ones on the edges with other methods.
If wild campanula has infested an area of a perennial planting, like daylilies, black-eyed Susan, or ground cover, the most effective method is to dig up the whole planting. Pick out and even rinse out any remnants of campanula you can detect. Dig up the soil to a depth of a least 9 inches and further pick out any remnants of campanula you can detect. Then replant, and be prepared to further attack any bits of campanula that sprout anew.
If you choose to use a non-organic weed killer, this is one case in which the practice might be well justified. A non-selective herbicide like Roundup is probably the most effective choice, though that kills all plants it touches, so it’s tricky to use in a flower bed. And, as with all garden products, actually read the package instructions — even if it means pulling out your reading glasses to see that tiny print — and follow them to the letter. Otherwise, not only are you being not very environmentally responsible, but you also may be wasting your time and money by not applying it properly.
Controlling wild campanula is a battle on all fronts and can take multiple seasons, but the alternative is allowing this garden bully to beat out other, more desirable plants. Persistence will pay off.
Veronica Lorson Fowler is co-publisher of The Iowa Gardener website at theiowagardener.com.