Calibrachoa, or million bells as it is commonly known, is a popular member of the ornamental flower garden. The plant’s small flowers, which resemble petunias, are a great addition to the edge of raised beds or containers, where they can spill over the sides creating an eye catching floral waterfall effect. Calibrachoa’s trailing habit also makes it ideal for hanging baskets.
Million bells come in a range of colors including yellows, reds, pinks and cream. You can find solid one color flowers, two tones varieties, patterned, double and even striped blooms. These delicate flowers sit on a cluster of compact, oval shaped leaves.
A versatile, reliable annual calibrachoa is hardy in USDA Zones 9 to 11. Best planted in the spring, the plants flower throughout the summer, providing a key source of pollen for butterflies and other pollinators. Million bells continues to flower until the first frosts of winter hit.
Colorful and attractive, million bells are a reliable addition to the flower garden.
While these plants are winter hardy, they are commonly grown as an annual in cooler climates. Growers in milder areas can also grow calibrachoa as a perennial.
Attractive and resilient, calibrachoa is a prolific bloomer that is quick to grow and easy to care for. This is your guide to growing calibrachoa.
Different Calibrachoa Varieties
A member of the Solanaceae family, some authorities such as the RHS do not recognise calibrachoa as a separate variety of plant. Instead they are classed as a petunia cultivar and are officially described as Petunia Million Bells.
Most calibrachoa varieties reach a height of 6 to 12 inches. They can produce trailing stems up to 30 inches in length and have a sprawling habit of between 12 and 24 inches.
While they may not be officially recognized, there are numerous calibrachoa varieties available. Some of the most popular include:
- Calibrachoa Superbells Pomegranate Punch, this cultivar produces attractive velvet-red flowers that are dark at their center, becoming lighter as they reach the edge of the petal.
- Million Bells Terra Cotta is prized for its orange blooms that are decorated with red and gold streaks.
- C. MiniFamous Double Blue produces double flowers in a deep purple-blue shade.
- C. Cabaret Hot Pink, as the name suggests, is known for its bright pink flowers.
- C. Cabaret Purple Glow is known for its attractive purple blooms.
- Superbells Grape Punch is a hybrid variety that produces burgundy or purple flowers with a yellow eye.
There are also a series of reliable hybrid cultivars available. Known as Kabloom these can be grown from seed and come in shades of blue, red, yellow, pink and white.
As well as solid colors, you will also find striped and patterned varieties.
You will find calibrachoa in most garden stores. More unusual varieties and seeds can also be purchased from plant nurseries.
Calibrachoa can be started from seed or purchased as small potted plants, ready for transplanting into the garden. While purchasing young plants is easy, growing from seed is more affordable and offers you access to a wider range of plants.
Growing Calibrachoa from Seed
Start your seeds around 8 weeks before your last predicted frost date.
Fill a tray or pots with fresh potting soil and moisten. Sow seeds as thinly as possible. Do not cover the seeds. They need as much light as possible to germinate.
Place the seeds in a propagator or in a warm, light position. The Super Sprouter Propagator Kit is ideal for seed germination. It’s built-in grow light enables you to maintain the ideal conditions for germination.
Keep the soil evenly moist, misting with a fine spray when it begins to dry out. The temperature should remain between 70 and 75 ℉.
Germination usually occurs within 14 days. In cooler conditions this may take a little longer.
Allow the seedlings access to as much light as possible, placing them either on a light windowsill or beneath grow lights.
When the seedlings have 2 sets of true leaves thin them out. Each seedling should have room to grow.
After about 4 weeks of steady growth apply a dose of houseplant fertilizer diluted to half its strength.
Allow the seedlings to grow on before hardening them off outside once all danger of frost has passed.
Where to Plant Calibrachoa
Calibrachoa can be planted in beds or borders. However, the plants tend to do better in pots or hanging baskets.
While calibrachoa are fairly heat and drought tolerant you should not regularly allow the soil to dry out. Ideally the ideal temperature should remain between 55 and 65 ℉. Hot weather can stress the plants, as can dry soil.
Misting the plants during warm periods helps to keep them cool. Misting also helps to revive foliage that is wilting in the sun. Do not mist your plants during the middle part of the day when the sun is directly overhead. This can burn the leaves. Instead mist either earlier in the morning or in the late afternoon. The Yebeauty Plant Mister Spray creates a fine mist, evenly covering the entire plant.
Calibrachoa are surprisingly cold tolerant. Just make sure that you harden them off before planting outside. Most varieties tolerate a light to mild frost.
Million bells do well in both beds and pots. Just make sure they are in a sunny position and the soil is well draining.
How Much Light do my Plants Need?
If you want your million bells to be at their absolute best, the plants must receive at least 6 hours of sunlight every day.
Million bells will tolerate partial shade but flowering may now be as prolific. If you are in a warmer USDA zone, planting in partial shade is preferred. This helps to keep the plants cool during the warmest part of summer.
Finding the Perfect Soil
If you are planting in a bed, work the soil over well before planting. Dig in plenty of organic material. This enriches the soil and improves drainage. The soil should be a neutral pH, or slightly acidic.
Fill pots or baskets with fresh, quick draining potting soil. Good drainage is key.
Calibrachoa can be planted outside as soon as the last predicted frost date passes. Remember to harden off your plants before planting outside.
Try to plant or repot your million bells as soon after purchasing as possible. Often calibrachoa plants are root-bound, or almost root-bound, when you purchase them.
Make a hole in the soil large enough to hold the root system of the plant. If you are unsure how large the hole should be, place the plant, still in its pot, in the hole. The pot should fit comfortably in the hole. The top of the pot should be level, or slightly below the soil line.
Before planting, work a slow release fertilizer into the bottom of the hole.
Work the soil over well before planting. Loosening the soil and removing stones and weeds helps to improve drainage.
If you are planting in a pot, make sure that the pot is clean and has plenty of drainage holes in the bottom.
Carefully remove the plant from its pot. If removal is difficult, squeeze the sides of the pot to loosen the soil. If this doesn’t work, try cutting away the sides of the pot. Loosen the root ball, brushing away any old soil in the process.
Position the plant in the hole so that the top of the root system sits slightly below soil level. When you are happy with the position of the plant, backfill the hole and gently firm down the soil. Water well.
Covering the soil with a layer of mulch helps to keep the root system cool. Additionally an organic mulch slowly breaks down, further enriching the soil and nourishing your plants.
Space the plants 6 to 12 inches apart. Varieties with a greater spread require more room than smaller cultivars. Consult the information on the plant label for exact distances.
Caring for Calibrachoa
Once planted these are pleasingly easy to care for plants. Sunlight, a little food and water is all the encouragement that these plants need to flower profusely.
If you are planting in beds make sure to weed the soil well before planting. Continue to keep the beds as weed free as possible while the plants are growing. Quick growing weeds can smother other plants, starving them of light, moisture and nutrients.
When to Water
Calibrachoa likes to be well watered. This doesn’t mean that you should allow the soil to become waterlogged. Wait until the top inch to two inches of soil is dry to the touch.
To test how dry the soil is, stick your finger in to about the second knuckle. If your finger is dry, water well. For a more scientific way to gauge the moisture content of your soil, try a moisture meter. The PentaBeauty Soil Meter, not only provides an accurate reading of your soil’s moisture content but also tells you the pH level of your soil and how much light your plants are receiving. This is all valuable information when caring for plants.
Keep your plants well watered, particularly during the warmest months of summer.
Plants growing in pots require more frequent watering than those growing in beds. If you are watering plants in containers water until water drains out of the drainage holes in the bottom of the pot.
How frequently you need to water depends on the conditions you are growing in. In the warmest areas you may need to water plants in pots twice a day. Mulching around the roots helps to keep the soil cool and conserve moisture.
Fertilizing Million Bells
Calibrachoa are heavy feeding plants. An application of slow release fertilizer is a good low maintenance way to meet their nutritional needs. Alternatively a liquid or water soluble fertilizer can be diluted in a watering can for easy incorporation into your regular watering routine.
Apply a 20-10-20 fertilizer to promote flowering. A slow release fertilizer should be applied once every two weeks. Do not over fertilize the plants. If you are unsure how much fertilizer to give, consult the information on the side of the fertilizer packet.
Fertilizing towards the end of the summer encourages late flowers to bloom.
Leaves turning a pale shade of green or yellow is an indication that they require more fertilizer.
Pruning Million Bells
Calibrachoa is regarded as a self cleaning plant. This means that you do not need to deadhead it to keep it in flower. However, the plant will appreciate cutting back at the end of summer.
Pinching back branch tips encourages the plant to branch out and more flowers to form.
You can also cut the branches back to about half their length in mid-season. Following this an application of fertilizer will help to rejuvenate the plants, encouraging flowers to continue forming until the end of summer.
An easy to care for flower, lightly pruning the plant about halfway through summer encourages more flowers to form.
Calibrachoa is easily propagated by taking cuttings.
Use a clean pair of garden scissors to take cuttings from healthy stems. Your chosen stems should have buds that are yet to flower on them. The cutting should be taken about 6 inches from the tip. Remove the leaves from the lower part of the cutting.
Plant each cutting in a small pot filled with an even mix of peat moss and potting soil. Water well and place in a bright, well lit position. Keep the cutting warm, at least 70 ℉, and moist. A propagator helps to maintain a regular temperature.
Roots should form within a few weeks.
Once roots have formed remove your cuttings from the propagator and allow them to grow on.
Overwinter Calibrachoa Plants
In milder climates overwintering calibrachoa is an easy process.
Once flowering has finished cut the stems back to about 2 inches above the ground. Water sparingly and cover with a 2 to 3 inch layer of organic mulch. Don’t forget to remove the mulch in the spring. This helps the new growth to emerge.
You can also try to overwinter calibrachoa in cooler climates but this may not be entirely successful. Growing cuttings on indoors overwinter before planting out the following spring is an easier option.
If you have planted calibrachoa in a bed or border, dig up the plants before the first frost and replant in a pot. Overwinter the pot inside before planting back out in the spring. Remember to harden off plants before replanting.
Plants in pots can be moved inside to overwinter before being returned to the garden the following spring.
Calibrachoa is a reliable companion plant. It can form part of the popular container garden “thriller, filler and spiller” planting scheme. Here the calibrachoa is the spiller part of the combination. Purple fountain grass, coleus, african daisy, geraniums can all act as the thriller while coral bells, lantana, sedges and marigolds are all reliable filers.
You can also combine million bells with other spiller plants such as verbena, nemesia and fan flowers for a pleasing trailing display. This can look particularly effective in baskets or as part of a living wall.
Planting alongside other flowers, such as coleus, as part of a “thriller, filler and spiller” planting scheme helps to create an eye catching effect.
Common Pests and Problems
Million bells are pleasingly low maintenance plants.
Often prevention is easier than cure. Correctly watering and planting in a favorable position helps to keep your flowers healthy. Spacing the plants so that air can circulate around them also helps to prevent disease.
Overwatering can cause mold or root rot to form. Plants wilting after you water them may also be suffering from root rot.
Some gardeners try to avoid planting calibrachoa at the same time as they plant tomatoes. Planting at the same time can attract more aphids to your plants.
While not classed as deer resistant, the plants are rarely troubled by the creatures.
Why is my Plant Failing to Flower?
A failure to flower is a sign that your calibrachoa is planted in unfavorable conditions. A lack of light is a common cause of plants failing to flower. A lack of warmth can also deter flowers from forming. This is particularly common in the spring.
In darker gardens, try planting your flowers in pots. You can then move the pots around your garden during the day, ensuring that the flowers stay in the sun for as long as possible.
In the summer, overheating or underwatering your plants can deter flowering. Nitrogen heavy fertilizers promote leaf growth at the expense of flower production. Fertilizers rich in bone meal or phosphorus help to counteract this. A 20-10-20 fertilizer also promotes flowering.
Million bells fills beds, baskets and pots with colorful flowers throughout the spring and summer months.
Versatile and attractive, whether you are growing them as an annual or a perennial calibrachoa is a reliable addition to the ornamental flower garden. Suitable for pots, beds and baskets these are resilient, low maintenance plants. Flowering until the first frosts hit, calibrachoa fills gardens with small colorful flowers and masses of foliage. It is easy to see why calibrachoa are so popular with pollinators and flower lovers alike.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.