The Canterbury Bell, scientifically known as Campanula medium, is a biennial flower known for its large, bell-shaped blooms. These plants can reach heights of up to three feet, introducing vertical interest to the garden. The flowers display colors commonly appearing in shades of blue, pink, lavender, and white. Growing these flowers from seed is a straightforward process that allows the gardener to produce a continuous display year after year.
Preparing and Sowing the Seeds
The ideal time to begin the process is indoors during late winter or early spring, approximately 8 to 10 weeks before the last expected frost date. Alternatively, seeds can be sown directly outdoors in a prepared bed during mid-summer to early autumn. Using a sterile seed-starting mix is recommended to prevent fungal diseases, and containers should be filled and moistened before sowing.
Canterbury Bell seeds are light-dependent germinators, meaning they require exposure to light to sprout. Therefore, the seeds should be surface-sown and gently pressed into the soil mix without being covered. Maintaining consistent moisture is important, achieved by misting the surface or watering from the bottom.
To encourage germination, the soil temperature should be maintained between 70°F and 75°F (21°C and 24°C). Seedlings should emerge within two to three weeks. If sowing outdoors in summer, a light layer of vermiculite can be dusted over the surface to help retain moisture while still allowing light penetration.
Nurturing Seedlings and Hardening Off
Once the seedlings have germinated, they must be provided with a strong light source to prevent them from becoming weak. If natural sunlight is insufficient, placing the young plants beneath grow lights for 14 to 16 hours daily is necessary. Continue to keep the soil evenly moist, but ensure the trays are never waterlogged, which can lead to damping-off disease.
When the seedlings develop their first set of true leaves, they can be thinned to allow the remaining plants space to grow. At this stage, introducing a weak solution of a balanced, water-soluble fertilizer can provide the necessary nutrients. Begin fertilizing at one-quarter to one-half the recommended strength every two weeks until the plants are ready for transplanting.
Before moving the young plants to the garden, they must undergo a process called “hardening off.” This involves gradually acclimating them to outdoor conditions, including wind, direct sunlight, and temperature fluctuations. Start by placing the plants in a protected, shaded spot outside for a few hours each day, slowly increasing the duration and exposure over a period of seven to ten days. Properly hardened plants are better equipped to handle the stresses of the outdoor environment.
Transplanting and First-Year Establishment
After the danger of the last frost has passed and the seedlings are hardened off, they can be moved to their final garden location. Canterbury Bells thrive in sites that receive full sun or partial afternoon shade. The soil should be well-draining, fertile, and enriched with organic matter like compost or aged manure.
Spacing the plants 12 to 18 inches apart is important for air circulation and preventing disease. When transplanting, handle the root systems carefully and plant the seedlings at the same depth they were growing in their containers. Watering the newly transplanted seedlings thoroughly helps settle the soil around the roots and reduces transplant shock.
The primary goal during this first year of growth is the establishment of the basal rosette. This cluster of leaves acts as the plant’s food storage and energy center, which is necessary for successful overwintering. Consistent watering throughout the first season is necessary, aiming for the soil to remain evenly moist, but not saturated.
Second-Year Bloom and Ongoing Maintenance
The Canterbury Bell is a biennial plant, which means its life cycle spans two growing seasons, with flowering occurring in the second year. The rosette established in the first year must survive the winter to produce the tall flowering stalks the following spring. In colder climates, applying a thick layer of mulch around the established rosettes in late autumn helps insulate the roots and protect them from temperature fluctuations.
Once the plant begins its second-year growth, applying a balanced, slow-release fertilizer in the spring will support the development of the flower spikes. As the plant blooms from late spring into mid-summer, removing spent flowers, known as deadheading, encourages the plant to produce more flower buds. Deadheading helps prolong the bloom period and maintains a tidy appearance.
To ensure a continuous supply of blooms, allow a few flowers to remain on the plant and mature into seed pods. Once the seeds ripen and drop, they will self-sow, beginning the biennial cycle anew. By staggering the planting of new seeds each year, you can bypass the two-year wait and enjoy the bell-shaped blooms annually.