HARDINESS: Zones 3 to 7
PREFERRED SOIL pH: Near neutral
PREFERRED SOIL TYPE: Fertile, well-drained
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Bell-shaped blue, violet, pink, or while flowers; for rock gardens, beds
SEASON OF INTEREST: Late spring through summer
FAVORITES: Tall C. persicifolia; short C. carpatica; heat-resistant C. glometala
QUIRKS: Some grow poorly where summer nights are hot
GOOD NEIGHBORS: Cohosh, foxglove, peony, stonecrop, sun rose
WHERE IT GROWS BEST: Sun to partial shade in loamy soil
POTENTIAL PROBLEMS: Plants become overcrowded after growing for a year or two
RENEWING PLANTS: Plants live for decades; divide every 3-4 years in spring or fall
CRITTER RESISTANCE: Good
DIMENSIONS: 6 in-4 ft (15.2 cm-1.2 m) tall, 1-3 ft |0.3-1 m) wide
Campanula in the Landscape
Beloved for blue, violet, pink, white, and purple bell-shaped blossoms, the campanulas in their many forms and sizes are all perennial summer charmers. Also called bellflowers, campanulas are easy to grow as long as your climate, or planting site offers cool nights to offset the warm days of summer. Campanulas are among the most care-free and finest flowers for perennial borders and rock gardens. Upright types team up beautifully with iris, foxglove, peonies, and perennial geraniums in mixed borders, and those that hug the ground are invaluable for the rich hues their flowers bring to rock garden areas.
A Medley of Bells
Carpathian bellflower (Campanula carpatica) does exactly what a good rock garden flower should do. It produces large, 2 in (5.1 cm) wide blue or white blossoms on petite, low-growing plants. The cultivars 'Blue Clips' and 'White Clips' mix well with yellow-flowered sedums, sun rose, and many other small rock garden plants in sunny, well-drained spots.
A more upright campanula that seldom fails is milky bellflower (C. latifolia), which grows to 4 ft (1,2 m) tall and produces softly rounded spikes of lilac flower clusters in midsummer. If old flower clusters are trimmed off, the bushy plants will stay in bloom for several weeks. Milky bellflower often reseeds itself here and there in the garden, but it is far from invasive.
There are many other upright campanulas to try, all of which need well-drained soil of average fertility. Peachleaf bellflower (C. persicifolio) produces very large, upward-facing blossoms on 2 ft (0.6 m) tall stems. While all campanulas are relatively free of pests, the campanulas described above grow best where summer nights are cool. In the high heat and humidity of summer, they can be subject to crown rot, a fatal, incurable fungal disease.
Less picky about weather is a very different species that grows as a blooming summer groundcover. Commonly called Serbian or Dalmatian bellflower, C. porschurskyono produces underground runners that quickly establish a low clump, only a few inches high but several feet wide. In sun or shade, this lavender-flowering campanula spreads vigorously, so site it with care. Another heat-resistant species is the clustered bellflower (Cglomerata). It is an upright plant that grows from 1 to 3 ft (0.3 to 1 m) tall.
Campanulas respond dramatically to fertile, well-drained soil, so dig in a 2 in (5.1 cm) blanket of good compost before setting out new plants in early spring. Space them 12-18 in (30.5-45.7 cm) apart, and keep the plants weeded to eliminate competition. After they have bloomed, cut the plants back by half their height to neaten the clump and stimulate a new flush of flowers. In the fall, mulch plants with a 1 in (2.5 cm) thick layer of compost to protect and fertilize them over winter.
Divide plants every third year in spring as new growth begins, or when clumps are crowded and flowering diminishes. Lift a clump, cut away healthy young crowns, and reset them in freshly dug soil, spacing them one-and-a-half times their height to allow room for them to spread as they mature. Keep the soil moderately moist for several weeks after transplanting so that the young plants do not dry out as they establish.