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Canterbury bells are biennials, so their schedule stretches over two growing seasons: sow in one, flower in the next. The perennial bellflowers repeat the same pattern every year, with winter cold as the trigger for the next season's flowers. The table sets the two side by side.
Timings shift with your climate. In cool-summer regions everything can run a little later and plants take more sun; in hot, humid regions the summer is a season to get through, with extra shade and restraint in watering.
| Season | Canterbury bells | Perennial bellflowers |
|---|---|---|
| Early spring | Last year's rosettes start to grow; feed lightly | New growth appears; slow-release feed; plant or divide |
| Late spring | Flower spikes open; sow next year's seed | Early kinds flower; support tall stems; watch for slugs |
| Summer | Deadhead, save seed, pull finished plants; nurse seedlings in part shade | Main flowering; deadhead; afternoon shade in hot areas |
| Early autumn | Plant out rosettes into limed soil | Divide congested clumps; plant new perennials |
| Late autumn | Rosettes settle in | Cut back to 2 to 4 in (5 to 10 cm); clear diseased foliage |
| Winter | Rosettes rest in the cold | Dormant; water pots sparingly |
Spring: waking up and first flowers
As the soil warms, overwintered Canterbury bell rosettes and perennial crowns start to grow. Give the perennials a slow-release fertilizer, put in supports for the tall kinds before the stems lengthen, and set out slug traps or bait around young shoots. Early spring is also a good time to plant new perennials or divide ones you missed in autumn.
By late spring the first bells open. This is also the time to sow next year's Canterbury bells, so the rosettes have the whole summer to build.
Summer: flowering and getting through the heat
Summer is peak bloom. Deadhead regularly, cut finished stems back, and feed again after the main flush. In hot, humid regions, make sure plants have afternoon shade and good air, and water only when the soil surface has dried.
Meanwhile the Canterbury bell seedlings need attention: prick them out young, keep them in part shade, and err on the dry side. Once last year's Canterbury bells have finished and set the seed you want, pull them out.
- Deadhead weekly Remove faded bells and spent stems to keep plants tidy and encourage repeat flowers on the perennials.
- Feed after the first flush Give the perennials a slow-release fertilizer once the main bloom is over.
- Watch the foliage Check for mildew, rust and mites in hot, still weather, and remove affected leaves early.
Autumn and winter: planting, dividing and resting
Early autumn is the busiest planting time. Set Canterbury bell rosettes out into limed, compost-rich soil while it is still warm, and divide congested perennial clumps so they root before the cold. Later in autumn, cut perennials back to 2 to 4 inches (5 to 10 cm) and clear away any diseased leaves.
Through winter the plants rest. That cold spell is what makes them flower, so leave them outdoors. Water pots only enough to stop them drying out completely, and protect plants only where the soil freezes solid for long periods.
If a bellflower sat in leaf all year without flowering, the usual cause is a winter that was too mild or a plant kept too warm. Give it a proper cold season outdoors.