Campanula is the genus name for summer blooming plants of the bellflower family (Campanulaceae). Campanula is comprised of around 300 species of annuals, biennials and perennials. Commonly known as bellflowers, campanulas vary in size and have a long blooming season, making them a popular garden plant.
Campanula species are divided into three groups: trailing types, mounding types and clumping types with tall, upright flower stems. Campanula foliage usually has toothed, or lobed edges and are mostly lance to heart-shaped. Its flowers are usually bell-shaped and have 5 petals or lobes. Campanulas range in height from 2 inches to 5 feet in height and 12 to 36 inch width. Flower colors range from blue, purple to mauve and white and pale pink.
Campanulas are generally very hardy plants and grow in sun or partial shade, but thrive with plenty of sunshine. Campanulas prefer well-drained soils, high in organic matter. Some species are well-suited to rock gardens and like grittier soils, and tall varieties benefit from staking for support.
Campanulas benefit from feeding in spring with well-rotted compost and bone meal and fertilization two to three times during the growing season, according to the University of Washington master gardener literature.
Remove old Campanula flowers for longer displays of blooms and divide your plants in early spring or August when they become crowded. Propagate Campanulas from seeds or cuttings.
Campanulas are frost tolerant and prefer nights below 70 degrees Fahrenheit for best growth. Campanulas grow in USDA hardiness zones 3 through 9, depending on the species.
Campanulas are often used in rock gardens or borders, depending on the species. Low-growing Campanulas are useful as ground covers in mixed perennial borders. Campanulas are listed as potentially invasive species in some locations, according to extension literature published by the University of Vermont. Plant campanulas in containers either in or on the ground if invasiveness is a concern.
Campanula carpatica has bell-shaped, upturned flowers of blue, purple or white and flowers late spring to summer.
Campanula takesimana produces white-pink flushed, spotted with maroon. It is a spreading variety suitable for use as a groundcover, not low-growing, however. C. punctata is similar to C. takesimana, but is smaller, and more compact.
Campanula rotundifolia, a very hardy species is also known as bluebells of Scotland, and is a blue-violet, pendulous flower with a low-growing habit.
Campanulas are relatively pest free, but may be bothered by aphids and mites. A home remedy of 3 tbsps. of dishwashing liquid mixed with 1 gallon of water sprayed on foliage every 5 or 6 days is one method to control mites. Rubbing alcohol, applied with cotton balls, is also effective for eliminating spider mites, aphids and white flies. Rinse the plants with water sprayed from a garden hose a few hours after application. Use caution when using any remedy and test on a small number of plants to evaluate any toxic effect.