Creeping bellflower (Campanula rapunculoides) is a perennial that often spreads into the lawn from areas where it was originally intended for use as an ornamental. In moist, shady locations this weed can become very invasive. The basal leaves are heart-shaped while the leaves on the flower stalks are more narrow. The pretty, bell- shaped flowers range in color from deep blue to purple. Mowing can prevent flowers from forming.
If bellflower is growing in your lawn you can dig it out. It has rather deep, horizontal fleshy roots, in addition to a shallow tuft of fibrous roots. You must dig down at least 6" and several inches out from the plant to make sure you have gotten them all.
You might also consider using glyphosate (sold most often as Monsanto Roundup). Glyphosate is a non-selective herbicide that kills or damages any green, living plant tissue it contacts, so it must be used carefully. Mix some in a small container, then use a sponge to wipe or daub it directly onto the bellflower leaves, or use a small hand spray bottle to carefully spray it right onto the plant. Late spring (May and June) and early fall (September) are the best times of the year to use glyphosate. It should be applied when temperatures are in the 60-85 degree range, the wind is calm, and when no rain is expected for at least 24 hours. Repeat applications may be needed.
An alternative to spot treatment is to spray with a broadleaf herbicide containing triclopyr or a combination of 2,4-D and MCPP as its active ingredients. These herbicides must also be used with caution since they will kill or harm any broadleaved (non-grassy) vegetation that they contact.
The best time to apply broadleaf herbicide is late spring or early autumn when wind is calm and temperatures are between 60 and 85 degrees F. with no rain expected for at least 24 hours. Several applications, a week to ten days apart may be needed if the roots send up new growth. Please follow the label directions carefully.
If bellflowers are growing in your perennial, annual, or vegetable garden you will have to dig them out or spot kill them using glyphosate. Broadleafed weed-killers cannot be used in a garden, only in the lawn.