Million bells is a perennial that can survive winters only in USDA Plant Hardiness Zones 9 to 11. The coldest of these, Zone 9, has an average low temperature of 20 degrees to 30 degrees Fahrenheit. In colder zones, million bells will not survive the winter, so it is grown as an annual. Million bells should be set out after the last frost and covered when a late frosts threaten. It is tolerant of the heat and, unlike petunias, continue to bloom prolifically through the heat of summer.
Million bells is a sun-loving plant. Place it in the garden where it will get sunshine all day, as it grows best and produces the most blossoms in full sun but will tolerate some light shade. When exposed to too much shade, it produces fewer flowers.
Because million bells blooms so prolifically, it requires regular watering. However, too much water can lead to root or crown rot. When planting million bells in a container, be sure the bottom of the pot has adequate drainage. If planting in the garden, be sure the soil is well-amended and composted. Million bells is drought tolerant, but its flower production decreases with lack of water. Therefore, if nature does not provide enough water, supplemental waterings may be desired.
Million bells likes an acidic soil with a pH of 5.5 to 6.0. Whether grown in a container or a garden, routine fertilizing will keep them blooming all summer. A sprinkling of a couple of tablespoons of a slow-release 14-14-14 fertilizer around the base of each plant is recommended. Million bells does not need to be deadheaded because the plants are self-cleaning. Plants can be pruned back as needed to keep them neat.