Growing Campanula (Bellflower): A Complete Profile
By Growing Home Greens Team · August 10, 2026
Campanula, also called Canterbury bells, is a tall spring cut flower with a genuine quirk: it’s daylength-sensitive, needing short days as a young seedling to build enough stem length before it flowers under the long days of early summer.
Timing matters more than usual
Direct-seeding isn’t recommended; start seed indoors 6 to 8 weeks before planting out, and don’t cover it since it needs light to germinate. A fine layer of vermiculite over the top helps hold moisture without blocking light. Because of the daylength sensitivity, plants should be started in fall, winter, or very early spring rather than timed to the last frost the way most annuals are. Fall-sown plants that overwinter in an unheated tunnel produce very tall, vigorous growth and bloom in early June; winter-sown plants flower a few weeks later on shorter stems.
Spacing depends on the goal
For single-stem cuts, which finish faster and suit greenhouse production, space 4 to 6 inches apart. For multi-stem, well-branched plants better suited to outdoor growing where space is less precious, space 10 to 12 inches apart; expect 8 to 10 stems per plant with this method. Support is recommended either way.
Harvest and handling
Cut fresh once 2 to 3 of the lower buds on a stem have opened. Keep cut stems upright rather than laying them flat, since the flower spikes bend easily and don’t recover once bent.
Campanula has no recorded companions or antagonists in our data. See the full companion guide for campanula for how it’s tracked. Given its unusual daylength requirement, it needs a fall or winter slot in the Garden Designer’s seed-starting calendar, well outside the normal spring-sowing window.
Source: Campanula (Bellflower): Key Growing Information, Johnny’s Selected Seeds.
Companion planting guide for Campanula (Bellflower) · Find your planting dates
Typically viable in USDA zones 2-11. Not sure your zone? Look it up by ZIP code.
Method: Start indoors: Start indoors from seed, then transplant outside. Campanula (Bellflower) needs a head start most zones can't give it by direct-sowing alone.
See exact start-indoors, direct-sow, and harvest dates for your zone →
How many Campanula (Bellflower) plants fit per square foot?
Spacing: 2 per square foot (square-foot-gardening spacing). Mature height: 2.5-3.5 ft.
Varieties worth considering
- 'Champion II White' campanula: Johnny's Selected Seeds' pelleted F1 campanula line, described as uniform and productive for cut-flower use; the pelleted seed makes precise sowing easier given how small campanula seed is. (source)
- 'Champion II Deep Blue' campanula (best for: true blue color): Johnny's Selected Seeds describes this as a uniform, productive cut flower in the same pelleted F1 line as Champion II White, in the deep blue that gives campanula its common name of bellflower. (source)
Cited from the source shown next to each variety. We haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement.
Where to buy campanula seeds
As an Amazon Associate we earn from qualifying purchases. Some links on this page also go to other retailers we may earn a commission from as an affiliate, at no extra cost to you. We only recommend products with a genuine consensus of positive, independent reviews. See the sources cited on each item.
See it growing
Search YouTube for "growing campanula (bellflower)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
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Growing Campanula (Bellflower): A tall spring cut flower that's daylength-sensitive, needing short days as a young seedling to build stem length before it flowers well.
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