Use your fingers or pruning shears to remove dead flowers during the growing season. This encourages the Canterbury bell to produce new blooms.
Wait until the Canterbury bell finishes blooming in early summer to cut it. Snap off the foliage and flower tendrils with your fingers.
Cut back only dead portions of the Canterbury bell in the fall. Wait until the soil freezes, and then cut back the entire plant to within 1 inch of the soil and cover it with pine needles or branches.