Gadenin日本語Get the appTwo kinds of campanula, two kinds of care
Canterbury bells are biennials: you raise them, flower them once, and pull them out. The perennial bellflowers stay put for years and are cared for like any hardy border plant. The basics of site and soil overlap, but the perennials vary a great deal in height and habit, so it helps to know which one you have.
Most perennial bellflowers are very hardy and stay outdoors all winter. They struggle far more with heat and humidity than with cold, and the tougher kinds, such as milky bellflower and the spotted or Korean hybrids, are the ones to choose for warm, sticky summers.
| Plant | Height | Habit and notes |
|---|---|---|
| Canterbury bells (C. medium) | 18 to 36 in (45 to 90 cm) | Biennial; big single, double or cup-and-saucer bells |
| Clustered bellflower (C. glomerata) | 12 to 24 in (30 to 60 cm) | Tight heads of upward-facing bells |
| Milky bellflower (C. lactiflora) | 2 to 3.5 ft (60 to 110 cm) | Pyramid-shaped heads; deep roots; among the toughest |
| Peach-leaved bellflower (C. persicifolia) | 2 to 3 ft (60 to 90 cm) | Open cup-shaped bells, double forms too; dislikes muggy summers |
| Spotted and Korean bellflowers (C. punctata, C. takesimana and hybrids) | 1 to 4 ft (30 to 120 cm) | Long hanging tubular bells; spread by rhizomes; more heat tolerant |
| Serbian bellflower (C. poscharskyana) | 4 to 12 in (10 to 30 cm) | Star-shaped flowers; spreading ground cover; takes heat and cold |
| Chimney bellflower (C. pyramidalis) | 3 to 5 ft (90 to 150 cm) | Tall spires in summer |
| Trailing kinds such as C. x haylodgensis 'Elizabeth Oliver' | Around 4 in (10 cm) | Small mats for pots, walls and rock gardens |
Light and air
Where summers are cool, give bellflowers full sun and they will flower hardest. Where summers are hot and humid, shade them from the afternoon sun and keep the crown itself out of baking sun, for instance with a low neighbor or a mulch of grit. Morning sun and bright afternoon shade is the sweet spot in warm regions.
Good air movement matters as much as light. Crowded, still plantings are where powdery mildew, rust and crown rot take hold. Leave room between plants, avoid tucking them against a wall in a dead corner, and thin out congested clumps rather than letting them knit into a solid mat.
Soil, beds and containers
Bellflowers need soil that drains quickly but does not dry to dust. The perennials put down a taproot that reaches about 8 inches (20 cm), so dig deeply. On heavy clay, raise the bed or plant on a gentle mound and work in plenty of compost and grit. Canterbury bells in particular dislike acid soil, so lime beds that run acidic before planting.
In containers, a mix of about six parts potting soil, two parts medium grit or pumice and two parts leaf mold works well. Use a pot with generous drainage holes and a depth that suits the taproot rather than a shallow bowl, except for the small trailing kinds, which are happy in shallow pans.
- Choose the timing Plant perennials in autumn or early spring, when roots are actively growing and the weather is mild.
- Space them properly Set perennial bellflowers 16 to 20 inches (40 to 50 cm) apart so air can move between clumps as they fill out.
- Plant at the same depth Keep the crown level with the soil surface. Burying it invites rot; leaving it proud lets it dry out.
- Water in well Soak the planting hole after firming in, then water as the surface dries until the plant is clearly growing.
Watering and feeding
While plants are in active growth, water when the surface of the soil has dried. In winter dormancy, water sparingly; pots need only enough to keep the mix from drying out completely. More bellflowers are lost to cold wet roots than to drought.
Go easy on fertilizer. Work only a little base feed into the soil at planting. Then give a slow-release fertilizer as growth starts in spring and again after the main flowering. Heavy feeding gives soft, floppy growth that mildews easily and flowers less.
Deadheading, cutting back and winter
Snip off faded bells regularly through the flowering season, and cut spent stems down to fresh growth once a stem is finished. This keeps plants tidy, prevents unwanted self-sowing, and on many kinds brings on a second, smaller flush.
In autumn, cut perennial bellflowers back to 2 to 4 inches (5 to 10 cm). They are hardy outdoors and only need protection where the soil freezes solid for long periods; a loose mulch or moving pots against a sheltered wall is enough. Pull Canterbury bells out once they have set the seed you want.