Companion Plants for Campanula Glomerata Superba

Trees

• Choose deciduous trees with open, airy canopies to plant with bellflowers. The Allegheny serviceberry (Amelanchier laevis) is hardy in Zone 4 to Zone 9 and prefers sun to partial shade. It tolerates a range of soil types and grows to 25 feet with a similar spread. This tree has an open, spreading canopy and blooms with white flowers in the spring. Its berries attract birds. The fringe tree (Chionanthus virginicus) grows to 20 feet tall with a similar spread and has an airy, spreading crown. It is hardy in Zone 3 to Zone 9, and thrives in sun to partial shade and well-drained soil. The fringe tree produces fragrant white panicles in the spring, followed by blue fall fruits.

Shrubs

• Choose shrubs with an open growth habit that don't create too much shade for the clustered bellflower. The salt myrtle (Baccharis halimifolia) is hardy in Zone 5 to Zone 9 and grows to 12 feet tall with a 7-foot-wide spread. This semi-evergreen to deciduous shrub grows well in sun to partial shade and tolerates a range of soils. It produces long-lasting, fluffy white flowers and tolerates drought, heat and salt. The littleleaf boxwood (Buxus microphylla) has dense, evergreen foliage but only grows to 4 feet tall. This compact, rounded shrub is hardy in Zone 6 to Zone 9 and prefers sun to partial shade and well-drained soil. It blooms in the spring with aromatic bee-attracting flowers.

Ground Covers

• Ground covers help reduce unwanted weeds in your flowerbeds. Companions for bellflowers include wooly yarrow (Achillea tomentosa), an evergreen that grows from 6 to 12 inches tall. It blooms with clusters of bright yellow flowers that contrast nicely with the bellflower's purple blossoms. Wooly yarrow has gray-green foliage and is hardy in Zone 3 to Zone 8. It prefers sunny sites with well-drained soil. Green and gold (Chrysogonum virginianum) also produces yellow flowers. This semi-evergreen perennial is hardy in Zone 5 to Zone 9 and grows to 9 inches tall. It thrives in sun to partial shade and any well-drained soil. Green and gold tolerates some foot traffic.

Perennials

• Perennial flowers live and bloom for at least three years. Companions for the clustered bellflower include the hyssop (Agastache foeniculum), a 3-foot-tall perennial that thrives in full sun and well-drained soil. Hyssops bloom with purple, blue and pink spikes of flowers in the summer. They are hardy in Zone 5 to Zone 9. The blackberry lily (Belamcanda chinensis) also prefers full sun and well-drained soil. This perennial grows from 3 to 4 feet tall and produces red and orange flowers in the summer, followed by blackberry-like fruits. It is hardy in Zone 5 to Zone 10.