American Bellflower Campanulastrum americanum
American Bellflower is an annual wildflower native to Canada and the lower 48 states. It grows to 6 ft and blooms Jul in full sun, with brown fruit.
More about this plant
Campanula americana, the American bellflower, or tall bellflower, is an herbaceous wildflower and a member of the Campanulaceae family. Common binomial synonyms are Campanulastrum americana and Campanulastrum americanum. American bellflowers are native to the Eastern United States and Canada, often found growing along stream banks and woods. They bloom in the summer months with light blue to purple flowers. American bellflowers can be annual or biennial plants, depending on the season of germination. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Full sun
- Soil & moisture
- Medium moisture
- Soil pH
- 5.5–7.5
- Fertility need
- Medium
- Adapts to
- Coarse (sandy), Medium (loam), Fine (clay)
- Hardiness
- USDA zone 13+
- Height
- 6 ft
- Spacing
- 2–3 ft apart from USDA planting density
- Spread
- None — clumping
- Growth rate
- Rapid
- Growth form
- Single crown
- Lifespan
- Annual
- Foliage
- Broadleaf · medium texture
- Active growth
- Spring through autumn
- Fruit
- Brown
- Flower colour
- Blue AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
- Propagate by
- Seed, Container
- Seed starting
- No stratification needed
- Seeds ripen
- Summer – Autumn seed-collection / harvest window
- In the trade
- Contract growing only
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →✦ Bees 17 bee visitors
17 native & managed bee species are documented visiting American Bellflower — the 12 most-recorded:
Related plants
More Campanulastrum →
How we know this (3) Methods & honest limits
A recorded categorical fact: each species is tagged C3 (standard), C4 (heat/water-efficient) or CAM (succulent, night-time CO₂ uptake) — or a facultative combination. We only show a trait card for the noteworthy C4/CAM cases; C3 is the unremarkable majority, kept in the data but not surfaced as a card.
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (28) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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