Campanula (Bellflower) in Zone 4a & 4b

Campanula medium

When to plant campanula (bellflower) in zone 4b

Zones 4a and 4b share the same average frost dates in our data, so this page covers both.

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.

Spacing: 2 per square foot (square-foot-gardening spacing). Mature height: 2.5-3.5 ft.

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.

How campanula (bellflower) fits zone 4's season

Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Campanula (Bellflower) needs about 120 days from transplant to first harvest.

Good companions

No standout companions recorded yet for Campanula (Bellflower).

Where to buy campanula seeds

• Botanical Interests
• True Leaf Market
• Burpee
• High Mowing Organic Seeds

See why we recommend these suppliers →

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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)

← Back to the full zone 4b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →

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Growing Campanula (Bellflower) in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.

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