Calibrachoa, also known as million bells, is one of the most popular plants for growing outdoors in containers. It comes in a rainbow of colors, in solids and two-tones, stripes, patterns, and stunning double blooms. Calibrachoa is a prolific bloomer and produces 1-inch blossoms that resemble tiny petunias. The compact leaves are oval-shaped and a bit sticky.
In most growing zones, million bells is best planted or repotted in the spring. It can bloom continuously through the growing season, and its flowers attract butterflies and hummingbirds. It's also a fast grower and quickly reaches toward the ground as a "spiller" when grown as a container plant. Because of its trailing habit, it looks great in hanging baskets, bowls, or mixed containers.
|Common Name||Calibrachoa, million bells, trailing petunia, mini petunia|
|Botanical Name||Calibrachoa group|
|Plant Type||Herbaceous perennial flower often grown as an annual|
|Mature Size||6–12 in. tall, 12–24 in. wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Moist, rich, well-drained|
|Soil pH||5.0–6.5 (acidic)|
|Bloom Time||Spring to fall|
|Flower Color||Coral, yellow, orange, red, pink, blue, purple, burgundy, lavender, cream|
|Hardiness Zones||9–11 (USDA); grown as an annual in all zones|
|Native Area||South America|
Although it is a short-lived perennial in very warm climates, Calibrachoa is grown almost everywhere as an annual. The plant is not hard to care for, but paying attention to its needs will keep it blooming from spring well into fall. While it can be planted in garden beds, the plant fares much better in containers.
This is considered a “self-cleaning” plant, meaning it doesn’t need to be deadheaded to keep blooming; however, it will benefit from a serious cutting back toward the end of summer. Deer don't seem very interested in Calibrachoa, although it is not classified as deer-resistant.
The plant blooms best with at least six hours of full sun, but it can tolerate partial shade—especially in warmer areas, where plants that get some shade are likelier to survive through the summer months. Insufficient sun exposure typically results in reduced blooming.
Calibrachoa likes fast-draining potting soil, so make sure your pot has good drainage. When planting in garden beds, amend with organic material to ensure richness, and make sure the soil drains well. Mulch is recommended to keep the soil moist and the root system cool.
Calibrachoa needs 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 plant's needs; watering requirements may change as the summer heats up. Take care not to overwater the plant, as this can encourage root rot.
Temperature and Humidity
The plant is pretty drought- and heat-tolerant, and even cold-tolerant, but to get the best blooms, don’t let it dry out repeatedly. It prefers temperatures between 55 and 65 degrees Fahrenheit. A hardened-off plant can be brought outdoors in the spring months and it can tolerate a mild frost. At the other end of the spectrum, hot weather and dryness can be stressful to the plant. You can revive wilted foliage with a daily misting, but be careful not to mist in direct sun, as this can burn the leaves.
This plant is a heavy feeder that can be fed with a slow-release fertilizer and/or a diluted liquid fertilizer regularly. For example, you can start with an organic, slow-release fertilizer mixed into your potting medium, and then give the plant a diluted liquid every couple of weeks throughout the season. Feeding is particularly necessary near the end of the season to promote late blooms. Be careful not to over-fertilize—follow the directions on the label of the plant food closely. Leaves turning light green or yellowish is a sign that the plant needs fertilizer, or possibly more sun.
Types of Calibrachoa
There are 28 different species in the Calibrachoa genus, but those used for garden cultivation are generally complicated hybrids derived from crossing various species. There are dozens of varieties of Calibrachoa available 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.
- C. 'Million Bells Terra Cotta' has orange flowers streaked with red and gold on stems trailing to 8 inches.
- C. 'MiniFamous Double Blue' has double flowers of deep blue-purple on a trailing plant with 10-inch-long stems.
- C. 'Superbells Pomegranate Punch' has velvety-red flowers that get darker toward the center and grows 8 inches tall.
- C. 'Kabloom' is a series of hybrid plants that can be grown from seed and they are available in pink, white, red, yellow, and deep blue.
Calibrachoa plants grown in gardens are hybrids that produce few seeds. And because many of the varieties are trademarked hybrids, vegetative propagation through cuttings is technically illegal. If you do attempt to propagate through cuttings, the process is as follows:
- Try to find a stem that has small buds but no flowers on it. Using a clean, sharp cutting tool, cut off the stem 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.
- Set the pot under bright light, and keep the cuttings moist and warm (about 70 degrees Fahrenheit). Roots should begin to develop within a couple of weeks.
Potting and Repotting Calibrachoa
Most million bells 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. If you repot the plant from its original container, be sure to loosen the root ball and add a slow-release fertilizer into a general-purpose potting mix. These are short-lived plants that won't require any more repotting. These spiller plants can live in a container of any material, but make sure there's plenty of drainage holes.
Common Problems With Million Bells
Besides battling aphids, the most common problem you'll encounter with the otherwise easy-going Calibrachoa plant is yellowing leaves. There are a few reasons for yellowing leaves:
- Iron deficiency (new growth will yellow)
- Nitrogen deficiency (old growth will yellow)
- Root rot
Root rot or mold infection can set in if these plants are overwatered. (Plants that wilt after watering may be suffering from root rot.) The best defense is to prevent these issues through good air circulation, proper water management, and good soil porosity.
Are million bells easy to care for?
The million bells plant has simple demands: It requires sunlight, enough water, and food. Just be on the lookout for an aphid infestation.
How fast do million bells grow?
This is a short-lived plant that will quickly fill a container with its trailing blooms.
What's the difference between million bells and petunias?
Million bells and petunias are often mistaken for one another because they trail, spread, and mound almost alike. However, million bells have smaller flowers than petunias, and they can be easier to care for, as well.