December 2007 Culture

Campanula glomerata Bellefleur Series By Paul Pilon

Bellefleur is a showy, well-branched perennial that is ideal for production in 5-inch or smaller containers. The series currently contains two colors, 'Bellefleur Blue' and 'Bellefleur White', which both produce compact, floriferous mounds reaching 4-6 inches in height.

Clustered bellflowers can be grown across a wide portion of the United States, throughout USDA Hardiness Zones 3-8 and AHS Heat Zones 9-11. The common name refers to the clustered arrangement of flowers at the top of the flowering stems. They are commonly used as accent plants, border plants, and in rock gardens and container plantings. In the landscape, the Bellefleur series naturally blooms from June to July.

Bellefleur campanula has many distinguishing characteristics. It bears numerous deep-blue or white flower clusters just above its attractive ovate foliage. The compact and uniform growth habit and floriferous nature of the Bellefleur series will liven up any perennial program. With these characteristics and its ability to bloom the first growing season, it is well suited for production in small container sizes and can easily be marketed alongside bedding plants.

Propagation

Campanula Bellefleur is propagated from seed. Light is required for germination; do not cover the seed with germination mix or vermiculite after sowing. Moisten the seed flats and move them into a warm environment where the temperatures can be maintained at 65-72¡ F for germination. It is best to germinate campanula in a germination chamber where uniform moisture levels and temperatures can be maintained.

Seedlings will emerge over a period of time ranging from 14 to 30 days after sowing. Following germination, reduce the moisture levels somewhat, allowing the growing medium to dry out slightly before watering to help promote rooting. Fertilizers are usually applied once the true leaves are present, applying 100-ppm nitrogen every third irrigation or 50 ppm with every irrigation, using a balanced water-soluble source. When the plugs are grown at 65¡ F, they are usually ready for transplanting in 7-9 weeks.

Production

As mentioned above, the Bellefleur series is suitable for production in small container sizes. Campanula performs best when grown in a moist, well-drained medium with a slightly acidic pH (6.0-6.4). Most commercially available peat- or bark-based growing mixes work well, provided there is adequate drainage.

When potting, the plugs should be planted so the original soil line of the plug is even with the surface of the growing medium of the new container. Planting them too deeply will lead to crop variability and losses. The best quality is achieved when they are grown in production facilities with high light intensities.

Campanula can be grown using light to moderate fertility levels. Growers using water-soluble fertilizers either apply 100- to 150-ppm nitrogen as needed or feed with a constant liquid fertilization program using rates of 50- to 75-ppm nitrogen with every irrigation. Controlled-release fertilizers applied as a topdress onto the media surface using the medium labeled rate, or incorporated into the growing medium prior to planting at a rate equivalent to 1 lb. of nitrogen per yard of growing medium, are effective methods of delivering nutrition to bellflowers.

Campanulas do not tolerate overly wet or dry conditions and should be grown under average irrigation regimes. When the root zones remain waterlogged, they tend to develop root-rot pathogens, which can quickly lead to crop losses. Overly dry growing conditions, on the other hand, can delay flowering and greatly reduce crop quality. When irrigation is necessary, water them thoroughly then allow the soil to dry slightly between waterings.

Bellefleur varieties have a naturally compact growth habit and will usually not require height-control strategies. However, during the winter months, during periods of low light levels, when grown at high plant densities or with luxury nutrient levels, excessive plant growth might occur, requiring some type of height-management strategy.

The growth of bellflowers can often be controlled by providing adequate spacing between the plants. It may be necessary, although not common, to use chemical plant growth regulators to control the growth of clustered campanula. In the northern parts of the country, I recommend a B-Nine (daminozide) at 2,500 ppm, Sumagic (uniconazole) at 5 ppm, or Bonzi (paclobutrazol) at 30 ppm. For toning and shaping purposes, one application is usually adequate.

Insects and Diseases

Campanula can generally be grown free of insects and plant pathogens. Aphids, spider mites, thrips and whiteflies may appear occasionally but typically do not cause significant injury to the crop. Botrytis, Pythium, and Rhizoctonia are the primary diseases that attack bellflowers. It is not necessary to implement preventive control strategies for any of these pests. Growers should monitor the crops regularly to detect the presence of insects and diseases early and to determine if and when control strategies are necessary.

Forcing

One of the most desirable characteristics of the Bellefleur series is its ability to bloom profusely the first year from seed. Although they are cold-beneficial plants, providing a cold treatment is not necessary for flowering. However, when a Bellefleur is vernalized, the time to reach flower is most often reduced by 2-3 weeks. I recommend growers consider using vernalized materials for early spring shipments to allow them to produce flowering plants quicker and switch to unvernalized materials later in the year.

Campanulas are long-day plants that require long photoperiods to flower. When the day length is naturally short, long-day conditions can be created by providing photoperiods of 16 hours, by extending the day if necessary, or using a four-hour night interruption during the middle of the night, providing a minimum of 10 foot-candles of light at plant level. Depending on the time of the year, production temperatures and size of the starter material, the Bellefleur series can generally be grown to a finished size in as little as 7-8 weeks. It is recommended to force campanula with temperatures ranging from 60-70¡ F. It takes approximately seven weeks to flower when they are grown at 65¡ F, while plants grown at 60¡ F will flower in eight weeks. To optimize plant development and produce high quality plants, I recommend growers force them under high light levels with temperatures of 65-68¡ F.

Availability

Campanula glomerata Bellefleur seeds are exclusively available to growers through S&G Flowers (www.sg-flowers-us.com). Plugs can be acquired from many reputable perennial plug producers or plant brokers.