Displaying magnificently rich-toned flowers of dark blue-violet, the macrantha or giant bellflower (Campanula latifolia var. macrantha) is a tall-growing perennial that blooms in early to midsummer. Native to eastern Europe, it is known to reseed itself across the garden, creating new stands of plants in succession. Sow seeds in the garden in very early spring, or lift and divide established plants in mid-spring. Grow in fertile, moist soils that are not acidic and have good drainage.
This perennial is native to eastern Europe, specifically the caucuses that reach across southwestern-most Russia, Azerbijan, Armenia, Georgia, northernmost Iran and northeastern Turkey.
Growth Habit and Description
The giant bellflower is an upright, tall, perennial with thick, unbranching stems that reach a height of 3 feet. The mid-green leaves are slender and lance-like and progressively get shorter toward the top of each stem. In late spring to midsummer, depending on the warmth of the climate, the stem tips bear loose clusters of bell-shaped flowers that are dark blue to deep blue-violet, attracting insects for pollination. The flowers are also somewhat tubular in shape and have five lobes. After flowering seed capsules are formed and when mature and dry split open to spread seeds across the ground.
Use giant bellflowers in landscapes in USDA Hardiness Zones 3 through 7. The soil should be fertile, rich in organic matter and moist with good drainage. The soil pH should not be acidic (lower than 6.5). Full sun exposures, those with at least 4 to 6 hours of direct sunlight, are acceptable, but the flower petals better retain their intense purplish blue colors if grown in partial shade, receiving no more than four hours of direct sun in the morning or late afternoon.
Seeds of giant bellflower should be sown in very late winter and early spring, such as February and March, and allowed to become small seedlings before being transplanted outdoors in mid-spring. Already established plants that are in clumps in the garden should be lifted and divided in mid-spring, March or April, and permitted to grow and flower in early summer in their new locations.
This bellflower prospers in regions that do not have hot summers, such as in USDA Hardiness Zones 3 to 6 or AHS Heat Zones 7 through 4. Irregular success is expected in USDA Zone 7; in warmer regions bellflowers will be an annual best grown in very early spring before temperatures regularly reach 80 degrees Fahrenheit.
The upright habit of this clumping perennial may need staking in the garden to prevent stem flopping from winds or heavy rains. After blooming the plant is mundane in appearance and best incorporated into a mixed border of plants that can provide visual interest when the bellflower is no longer blossoming.
The plant also produces good amounts of capsuled seeds that are scattered across the garden, causing new colonies of plants to establish. Make sure to cut off flower spikes when the flowers fade so seeds do not mature and spread in the garden.
Botanically, the giant bellflower is listed as Campanula latifolia var. macrantha, a naturally-occurring variant. However, some horticulturalists and nurserymen may refer to and write it as Campanula latifolia macrantha.