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The bellflower season starts in late spring and runs through summer, and by mixing species you can have campanulas in flower for most of that stretch. Canterbury bells are the showpiece of late spring and early summer, with stout spikes crowded with bells in blue, violet, pink and white, including double and cup-and-saucer forms.
The perennials follow their own timetables. Clustered and peach-leaved bellflowers overlap with Canterbury bells, milky and spotted bellflowers carry on into high summer, and chimney bellflower sends up its tall spires in summer. Serbian bellflower foams over the edge of a bed from late spring and often reblooms lightly later.
| Plant | Main flowering | Flower shape |
|---|---|---|
| Canterbury bells | Late spring to early summer | Large upright bells, single or double |
| Clustered bellflower | Early summer | Dense upward-facing clusters |
| Peach-leaved bellflower | Early to midsummer | Wide open cups on slim stems |
| Milky bellflower | Early to late summer | Large pyramid heads of small bells |
| Spotted and Korean bellflowers | Early to late summer | Long hanging tubular bells |
| Serbian bellflower | Late spring to summer | Small star-shaped flowers in sheets |
| Chimney bellflower | Summer | Tall spires of open bells |
Why a campanula does not flower
The most common reason is not enough winter chill. Campanulas need a stretch of cold to switch from leaf to flower. Canterbury bells sown too late, or grown in a mild winter, can make a rosette and simply wait another year. Perennials kept in a heated greenhouse or a warm porch over winter often sit in leaf all season. Keep them outdoors, where they feel the cold.
Other causes are simpler. Too much shade gives leaves without bells; heavy nitrogen feeding does the same. Clumps that have grown congested and woody in the middle flower less each year and need dividing. A Canterbury bell rosette that was still small going into winter may send up only a thin spike.
Getting more flowers from the same plants
Deadheading is the single most useful habit. On Canterbury bells, pinching off each bell as it fades lets the side buds open and stretches the display by a couple of weeks. On the perennials, removing whole spent stems usually prompts a second, lighter round of flowers later in summer.
Tall kinds such as peach-leaved, milky and chimney bellflower may need support in exposed gardens. Put in stakes or grow-through supports early, before the stems lengthen, so the plant grows into them rather than being tied up after it has flopped.
- Pinch individual bells Pick off faded bells on Canterbury bells every few days so the buds lower on the stem keep opening.
- Cut whole spent stems On perennials, cut a finished stem back to the leafy base or to a side shoot with buds.
- Water and feed after the first flush Give a slow-release fertilizer and a good soak after the main bloom to support any repeat flowering.
Campanulas as cut flowers
Canterbury bells, peach-leaved and milky bellflowers all make good cut flowers. Cut stems when the lowest bells are open and the upper ones are showing color, early in the morning while they are full of water. Strip the lower leaves and stand them in deep water in a cool spot for a few hours before arranging.
The stems bleed a little milky sap when cut. Rinse the cut end or give it a fresh snip under water and change the vase water every couple of days. Individual bells fade, but new ones keep opening up the stem for about a week.
Leave a few Canterbury bell stems uncut if you want to save seed for next year's plants.