June 2004

Campanula punctata ‘Bowl of Cherries’ By Paul Pilon

For over five centuries gardeners and landscapers have been utilizing campanula species to accent their gardens. With more than 300 species in the genus campanula, a number of forms and textures are available for gardeners to incorporate into today's landscape. Campanula punctata, commonly called the spotted bellflower, is a showy spreading type of campanula that is receiving much attention in recent years from perennial growers.

Campanula punctata 'Bowl of Cherries' is one of the newer introductions of spotted bellflowers from Terra Nova Nurseries, Tigard, Ore. It thrives in locations with partial to full sun throughout USDA hardiness Zones 5-9. Bowl of Cherries is a prolific bloomer, producing numerous dark purple-red bells on compact 15-inch mounds. When the old flower stems are removed, it will produce another flush of flowers.

Propagation

Bowl of Cherries is vegetatively propagated most commonly with tip cuttings by licensed propagators. Since a plant patent is being sought (PPAF), unlicensed propagation of this cultivar is prohibited.

Many growers propagate Campanula punctata cultivars by root cuttings. Root cuttings involve taking small pieces of the root, usually 2-3 inches long by 1?8-1?2 inches thick, and placing them vertically in a propagation media. This type of propagation is almost always performed during the winter months when the plants are not actively growing.

Production

Campanula punctata cultivars perform well in a wide range of growing mediums. They do seem to prefer mixes with good drainage. Bowl of Cherries is a moderate feeder and grows well under a constant liquid fertilizer program, receiving 75-125 ppm with each irrigation. The pH should be maintained at 5.8-6.2. I prefer to fertilize this crop by incorporating a controlled-release fertilizer into the growing mix at the time of planting. The incorporation rate should provide the equivalent of 1 lb. of nitrogen on a per-yard basis. For example, when using a formulation that contains 20 percent nitrogen such as 20-9-12, it would require 5 lbs. of the fertilizer to provide 1 lb. of elemental nitrogen. When cultivars of Campanula punctata are underfed, they exhibit signs of chlorosis, which can be easily remedied by irrigating with liquid fertilizer at twice the rate mentioned above. Water thoroughly as needed, allowing the soil to dry between waterings. The best quality is achieved when plants are grown in full sun or greenhouses with high light intensities.

Bowl of Cherries, with its compact growth habit, will usually not require plant growth regulators to control plant height. However, during the winter months, or during periods of low light levels, I have found it beneficial to apply growth regulators for toning and maintaining plant quality. B-Nine (Crompton/Uniroyal) and Sumagic (Valent) are very effective at reducing stem elongation and should be applied only as needed; beginning rates for Northern growers are approximately 2,500 ppm and 5 ppm respectively. For toning and shaping purposes one application should be adequate. When additional height control is necessary, make a second application 7-10 days after the first. Before applying chemicals, you should try environmental control measures. The height of these campanulas can often be effectively controlled by providing adequate spacing between plants and withholding water and nutrients.

Bellflowers are relatively free of serious problems associated with insects or diseases. The most common insect observed feeding on Bowl of Cherries is aphids. They can be controlled either on a preventative basis using systemic materials such as Marathon 60 WP (Olympic), Endeavor (Syngenta), TriStar (Cleary Chemical) or Flagship (Syngenta) or on an as-needed basis determined by a weekly scouting program. For container production, Bowl of Cherries is suitable for production in 1-quart to 1-gal. containers. For 1-gal. production I recommend planting two 72-cell plugs into each pot. When grown at 65¡ F, it will take approximately seven weeks to produce a 1-gal. plant of salable size with or without bloom. Blooming plants will occur when they reach the right maturity, are grown under the proper photoperiod or by following the recommendations listed below.

Forcing

Bowl of Cherries is an attractive perennial that is relatively easy to grow. When producing blooming plants, which is the goal, a few requirements should be met to ensure uniform, consistent, high-quality flowering plants.

It is recommended to begin the forcing process, before providing the other necessary requirements, with plant materials having at least six nodes. Using smaller materials will most likely lead to inconsistent and sporadic flowering. Bowl of Cherries has an obligate cold requirement and will not flower completely without this treatment. I recommend growers provide 10 weeks of exposure to temperatures below 40¼ F to satisfy this cold requirement. The cold treatment can occur in the plug stage or in finish containers.

Once the cold period is achieved, Bowl of Cherries, a facultative long-day plant, should be grown under long-day conditions by providing 16 hours of light or a 4-hour night interruption until flower buds are visible. Growers should ensure a minimum light intensity of 10 foot-candles during the night portion (dark) of the day extension or night interruption. When forcing Bowl of Cherries in the winter months, it is beneficial to increase the light intensity by using supplemental lighting (500-600 foot-candles) throughout the day. Higher light levels will help increase plant quality by producing a sturdier plant and is likely to increase the flower number as well.

Provided the juvenility and cold requirements have been satisfied, it will take 6-8 weeks to force Bowl of Cherries into bloom under long-day conditions when grown at temperatures ranging from 68-70¼ F. Growers commonly produce campanulas at temperatures ranging from 60-75¼ F. Increasing production temperatures will decrease the production time and may reduce plant quality. Research has shown that most campanula cultivars have improved quality characteristics such as improved flower number and flower size when produced at cooler temperatures. For the highest quality plants, I recommend growers force Bowl of Cherries with temperatures at 65-70¼ F when possible.

Availability

Bowl of Cherries is brought to the industry by Terra Nova Nurseries, Tigard, Ore. It is available to growers most commonly as finished plugs from Terra Nova or other reputable plug producers throughout the country. Garden centers and retailers can obtain this variety from a number of growers who offer finished containers; check your supplier's catalogs or availability listings.