Campanulastrum americanum (tall bellflower)

Campanulastrum spp.

American bellflower

Campanulaceae Eastern and central North America

Attracts Pollinators Attracts Butterflies

Native to North America

SunPart Shade – Full Sun

WaterMedium

HardinessZones 3–8

Overview

Campanulastrum spp. is a genus in the bellflower family (Campanulaceae), represented in gardens by the American bellflower, Campanulastrum americanum, a herbaceous plant of eastern North American woodlands. Plants form an erect, largely unbranched stem 3-6 feet (90-180 cm) tall and 1-2 feet (30-60 cm) wide, completing growth as an annual or biennial. The alternate leaves are ovate to lance-shaped, 3-6 inches (8-15 cm) long, with toothed margins and a thin texture. Flowers open along the upper stem in a leafy spike, each one flat and star-shaped, 0.75-1 inch (2-2.5 cm) across, in blue to violet with a pale central ring and a long, downward-curving style. This flat corolla separates Campanulastrum spp. from the bell-shaped flowers of related Campanula spp.. Bloom runs through summer into early autumn, and plants set seed in small capsules that scatter nearby. Growth follows moist, humus-rich soil in partial shade at woodland edges, stream banks, and clearings, though stems in full sun stay shorter. Because the plant depends on self-sown seedlings, it shifts position within a planting from year to year rather than holding one spot, and dense stands can crowd smaller herbs.

Native Range

The single widely grown species, Campanulastrum americanum, is native to the eastern and central United States and adjacent Canada, from Ontario and New York south to Florida and west to the Great Plains. It grows in moist deciduous woods, ravines, and shaded streamsides.

Suggested Uses

Plants are used in shaded native-plant and woodland gardens, along stream banks, and in naturalized borders where self-seeding is acceptable. The height places them toward the back of a planting, behind lower woodland perennials. The flowers support bees and other native pollinators.

How to Identify

Look for a tall, mostly single stem carrying flat, five-lobed blue to violet flowers about 1 inch (2.5 cm) wide, each with a white central ring and a protruding style that curves downward. The open, star-shaped corolla sets it apart from true Campanula spp., which carry nodding bell-shaped flowers. Leaves are thin, toothed, and taper to a point; the lower leaves have short stalks while the upper ones sit close to the stem.

Appearance

Size & Dimensions

Height3' - 6'

Width/Spread1' - 2'

Reaches mature size in approximately 2 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks

Summer Fall

Flowering runs from June to September, with each flower lasting a few days and opening in sequence up the stem. Across the genus the display concentrates in mid to late summer and extends into early autumn in cooler sites. Bees carry out most pollination before the capsules dry and split to release seed.

Detailed Descriptions

Flower Description

blue to violet

Foliage Description

green

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Sun

Requires 3-6 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.0(Neutral)

357912

Soil Types

loam silt

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1-2 years from seed to flowering

Care & Maintenance

Care Guide

Plants grow in moist, fertile, well-drained soil with a near-neutral to slightly acid pH of 5.5-7.0. Partial shade at a woodland edge matches the genus, though stems tolerate full sun where soil stays damp. Watering helps during dry spells, as the foliage wilts quickly in drought. Because the plant is annual to biennial, continuity in a garden depends on letting some capsules mature and drop. Seedlings move poorly once rooted, so they are generally left where they germinate. The tall stems rarely need staking, though those in open positions can lean.

Pruning

Formal pruning has no role with this genus. Spent flowering stems can be cut after seed sets to limit self-sowing, or left standing so capsules release seed. Cutting the whole stem at the base in late autumn clears the planting once growth has died down.