Calibrachoa, also known as million bells, is one of the most popular plants for growing outdoors in containers. A classic spiller plant, it has a trailing habit and looks great in hanging baskets, bowls, or mixed containers. It also works well in unusual containers, such as colanders or even plastic laundry baskets. Calibrachoa is a prolific bloomer and produces 1-inch blossoms that resemble tiny petunias.
Calibrachoa is not recognized as a separate genus by some authorities. The Royal Horticultural Society, for example, views them as a variety of petunia, giving them the name Petunia 'Million Bells'.
Calibrachoa comes in a rainbow of colors, in solids and two-tones, stripes, patterns, and stunning double blooms. The compact leaves are oval-shaped and a bit sticky.
|Botanical Name||Calibrachoa group|
|Common Name||Calibrachoa, million bells, trailing petunia, mini petunia|
|Plant Type||Herbaceous perennial flower often grown as an annual|
|Mature Size||6 to 12 inches tall, 12 to 24 inches wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Moist soil rich in organic material|
|Soil pH||5.0 to 6.5|
|Bloom Time||Spring through fall|
|Flower Color||Coral, yellow, orange, red, pink, blue, purple, burgundy, lavender, and cream|
|Hardiness Zones||9 to 11, USDA|
|Native Area||South America|
How to Grow Calibrachoa
Calibrachoa plants have simple demands: They require sunlight, enough water, and food. The plant is not hard to care for, but paying attention to its needs will keep it blooming from spring well into fall. While they can be planted in garden beds, they fare much better in containers.
Calibrachoa is considered a “self-cleaning” plant, and it doesn’t need to be deadheaded to keep blooming; however, they do benefit from a serious cutting back towards the end of the summer.
Calibrachoa plants bloom best with at least six hours of full sun, but they can tolerate partial shade—especially in warmer areas, where plants that get some shade are likelier to survive into the summer months.
Calibrachoa plants like fast-draining potting soil; make sure your pot has good drainage. When you plant them in garden beds, make sure the soil is well amended with organic material and has good drainage.
Calibrachoa plants need to be kept well hydrated but not water-logged. Add water only after the top inch or so of the soil dries out. To check if your plant needs water, stick your finger into the soil up to the second knuckle. If the soil feels dry at your fingertip, water deeply until it drains out of the bottom of your pot. Don’t water again until the soil dries out again.
Heat, wind, and lack of humidity can cause your soil to dry out quickly. Depending on your conditions, you may have to water as often as twice a day. Check the soil frequently, especially at the beginning of the season, until you get to know your plants’ needs; watering requirements may change as the summer heats up. Take care not to overwater these plants, as this can encourage root rot.
Temperature and Humidity
Calibrachoa plants are pretty drought- and heat-tolerant, and even cold-tolerant, but to get the best blooms, don’t let them dry out repeatedly. They prefer temperatures between 55 and 65 degrees F. Hardened-off plants can be brought outdoors in the spring months; most can tolerate a mild frost.
This plant is a heavy feeder and needs to be either given a slow-release fertilizer and/or fed a diluted liquid fertilizer regularly. Mix an organic, slow-release fertilizer into your potting medium and then give the plant a diluted liquid every couple of weeks. Be careful not to over-fertilize; follow the directions on the label of the plant food closely.
Potting and Repotting
Most calibrachoa plants are badly root-bound when you buy them—so much so that there is very little soil left in the pot. This means that your margin of error for watering is very slim and there isn’t much nutrition for the plants to use. When you pot or re-pot calibrachoa, make efforts to loosen the root ball and add a slow-release fertilizer into the potting mix.
The main method of propagating Calibrachoa is through cuttings.
- Try to find a stem that has small buds but no flowers on it. Cut this stem off at least 6 inches from the tip, then remove any lower leaves.
- Place your cuttings in an equal mix of half potting soil and half peat moss. Water well.
- Keep the cuttings moist and warm (about 70 degrees F) and set the pot under bright light. Roots should begin to develop within a couple of weeks.
Varieties of Calibrachoa
There are dozens of varieties of Calibrachoa, in a vast array of colors, including:
- Calibrachoa 'Cabaret Hot Pink': Produces loads of bright pink flowers on trailing stems up to 8 inches long
- C. 'Cabaret Purple Glow': Grows 12 inches wide and trails to 8 inches
- 'Million Bells 'Terra Cotta': Orange flowers streaked with red and gold on stems trailing to 8 inches
- C. 'MiniFamous Double Blue': Double flowers of deep blue-purple on a trailing plant with 10-inch-long stems
- C. 'Superbells Pomegranate Punch': Velvety-red flowers that get darker toward the center; grows 8 inches tall
Common Pests and Diseases
Root rot or mold infection can set in if these plants are overwatered. (Plants that wilt after watering may be suffering from root rot.) Calibrachoa plants are also susceptible to spider mites and aphids. Prevention in the form of good air circulation, proper water management, and good soil porosity is the best defense. Deer don't seem very interested in Calibrachoa plants, although they are not classified as deer-resistant.