Bellflowers have long been a favorite perennial of gardeners, landscapers and commercial growers. There are numerous species in production, each offering a different set of characteristics and uses. Campanula persicifolia has historically been used as a cut flower or backdrop in landscape settings as it commonly reaches 2-4 feet tall while blooming.
American Takii, Inc. (www.takii.com ) recently introduced an outstanding F1 hybrid called ‘Takion Blue’, a genetically compact variety that produces an abundance of lavender-blue flowers. Like other peach-leafed bellflower cultivars, the leaves are long and narrow, resembling those of the peach tree. This dwarf cultivar reaches 16 to 20 inches when in bloom and produces multiple flowering branches in the late spring and into the summer. One of the most notable attributes of ‘Takion Blue’ is that its flowers are held facing up and out — while many varieties’ are dangling or facing down — which reveals their richly colored 2- to 21/2-inch wide blooms.
Campanula persicifolia performs well throughout USDA Hardiness Zones 3 to 8 and AHS Heat Zones 9 to 1. With its compact growing habit and showy blooms, ‘Takion Blue’ can be grown in patio pots, mixed containers or as houseplants; in the garden, it is used as an accent plant, in border plantings or as cut flowers. Its flower power and ease of production make ‘Takion Blue’ ideal for many commercial perennial growers and a show stopper in the garden center.
Campanula ‘Takion Blue’ is an F1 hybrid propagated from seed. The seeds are small and may be difficult to handle; sow multiple seeds per cell. Do not cover the seed with germination mix or vermiculite after sowing, as they require light for germination. Moisten the seed flats and move them into a warm environment where temperatures can be maintained at 66-70° F for germination. It is beneficial to germinate campanula in a chamber where you can maintain uniform moisture levels and temperatures.
Seedlings typically emerge within seven to 10 days of sowing. Reduce moisture levels after germination, allowing the growing medium to dry out slightly before watering. 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. It takes six to seven weeks for plugs grown at 65° F in 288-cell trays to reach a transplantable size.
‘Takion Blue’ is suitable for production in medium-sized containers; 5-inch to gallon pots work well. Campanula performs best when grown in a moist, well-drained medium with a slightly acidic pH of 5.5-6.0. Most commercially available peat- or bark-based growing mixes work well, provided there is adequate drainage. For best quality, grow in production facilities with high light intensities. When planting, take care to not bury the crown of the plant too deeply. After potting, the original soil line of the plug should be even with the surface of the growing medium of the new container. Planting them too deeply will lead to crop variability and losses.
Campanula can be grown using light to moderate fertility levels. Growers using water-soluble fertilizers apply 75- to 100-ppm nitrogen with every irrigation or use 200 ppm as needed. Before planting, controlled-release fertilizers can be incorporated at a rate equivalent to 1.0 pound of elemental nitrogen per yard of growing medium or applied as a top-dress onto the media surface using the medium recommended rate on the fertilizer label. The roots can be sensitive to high fertility levels, especially under warm growing conditions; maintain low fertility levels under unseasonably warm production temperatures.
Grow plants under average irrigation regimes; ‘Takion Blue’ does not tolerate wet or overly dry growing conditions. When irrigation is necessary, water them thoroughly then allow the soil to dry slightly between waterings. You may need to increase the leach fraction under warm temperatures to prevent salts from accumulating in the root zone.
‘Takion Blue’ reaches about half the height of many C. persicifolia cultivars when flowering and will usually not require height control strategies. One or two 2,500-ppm applications of daminozide (B-Nine or Dazide), seven days apart, can be effective at reducing plant height when applied just as the flower stems are beginning to elongate.
Insects and Diseases
Campanula can generally be grown free of insects; aphids, caterpillars, leafhoppers, slugs, spider mites, thrips and whiteflies may appear occasionally but without significant injury to the crop. None of these insect pests require preventive control strategies, but routine scouting programs should detect their presence early enough to determine whether control strategies are necessary.
Under the proper environmental and cultural conditions, campanula also can generally be produced without the occurrence of plant pathogens. But several pathogens, including Ascochyta, Botrytis, Cercoseptoria, Phyllosticta and rust can cause foliar leaf spots; and crown and root rots can be caused by the pathogens Fusarium, Pythium, Rhizoctonia and Sclerotium. Manage the environment and prevent these pathogens by providing proper plant spacing, adequate air movement, humidity control, good fertility and watering practices, or, if desired, a preventive fungicide program using the appropriate crop protection products.
‘Takion Blue’ can be forced into bloom and are most commonly produced for early- to midseason sales. They have an obligate cold requirement for flowering. They can be either vernalized as a large plug (72-cell or larger) or bulked up in the final container size for at least six weeks before providing the necessary cold treatment. Provide at least six to nine weeks of cold temperatures (less than 44° F) before forcing them in the spring.
Following the cold treatment, they will flower under any photoperiod (day neutral) and can be forced into bloom under natural day lengths. The length of the photoperiod has no effect on the time to flower; however, plants will be slightly shorter when they are grown under short days.
The time to flower after vernalization is a function of temperature; at 65-68° F, they will flower in five to six weeks. They can also be grown in unheated structures or in outdoor production facilities for slightly later sales periods.
Seed of campanula ‘Takion Blue’ is available to growers through American Takii, Inc. (www.takii.com ). Plugs can be acquired from many reputable perennial plug producers or plant brokers.