Bell flower (Campanula spp.) is a genus of flowering plants consisting of over 300 different species, resulting in a wide variety of colors, growth habits and sizes. Campanula can bloom between late spring and early fall, producing blue, lavender, pink or white flowers. They grow to a mature height between 4 inches and 4 feet, depending on the species. Campanula is basic to grow in most temperate climates, especially in hardiness zones 3 through 8.
Transplant campanula seedlings outdoors in a well-drained, fertile after all danger of frost has passed in spring. Allow 12 to 18 inches of space between each campanula plant. Ensure the planting location receives full morning sun and partial afternoon shade.
Spread a 2-inch layer of mulch around the newly planted campanula. Start the mulch band about 3 inches from the base of the plant to allow room for growth. Refresh the mulch as needed, especially during the winter when the soil needs insulation to prevent heaving.
Water campanula plants deeply once per week during spring, summer and fall, providing about 1 inch of water weekly. Reduce watering to once every two weeks during winter. Do not water on weeks that receive heavy rainfall or the plant can become waterlogged and rot.
Feed campanula twice per year, once in late winter and again in early spring. Use a balanced 10-10-10 NPK fertilizer, applying approximately 1/4 pound of fertilizer per 25 square feet of campanula bed, or apply according to the manufacturer's instructions. Water both before and after application to prevent root burn.
Remove dead or faded flowers from stems only when all of the flowers on that stem have faded. Pinch them off as close to the stem as possible, and new blossoms will form within a few days. No further pruning of campanula plants is required.
Monitor the plants for pest damage from slugs, snails, mites or aphids. Control slugs and snails by removing them by hand or by sprinkling slug bait around the perimeter of the planting site. Spray the plants with a ready-to-use insecticidal soap spray at five day intervals to control aphids or other soft-bodied pests.