Calibrachoa, often referred to as “million bells®” or “tiny petunias,” is a genus of plants that originated from South America.
These plants, introduced to the market in the early 1990s, have quickly become a favorite among gardeners due to their continuous blooming and low-maintenance nature.
It is important to note that Million Bells® and Super Bells® are trademarked names in the industry, and should always be referred to as such, rather than simply as “million bells.”
With their trailing habit and compact form, they are perfect as a spiller in hanging baskets, window boxes, and garden beds.
The plant calibrachoa is a prolific bloomer, producing a rainbow of colors, from solid hues to stripes and speckle patterns. These plants produce the best blooms when they receive at least six hours of full sun each day.
They are also known for their self-cleaning nature, meaning they drop old flowers to make way for new ones without any assistance.
These fast growers are annual in colder climates and short-lived perennials in warmer regions. They are also deer-resistant, making them a great choice for gardeners who struggle with deer nibbling on their plants.
Despite their delicate appearance, these tiny petunias are quite hardy and can withstand a range of conditions, including partial shade and frost.
These popular outdoor container plants are stunning and surprisingly easy to grow. As a master gardener, I’ll share all the top tips and tricks for calibrachoa care so you can successfully grow them at home.
Botanical Name: Calibrachoa group
Common Name: Calibrachoa, million bells, trailing petunia, mini petunia
Family: Solanaceae
Plant Type: Herbaceous perennial flower often grown as an annual
Hardiness Zones: 9–11 (USDA); grown as an annual in all zones
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
Native Area: South America
Calibrachoa Care
Calibrachoa are fast growers and heavy feeders, requiring a slow-release fertilizer at the start of the growing season, supplemented by a water-soluble fertilizer for the best blooms.
These mini-petunias thrive in hanging baskets, window boxes, and garden beds with good drainage to prevent root rot. They prefer six hours of full sun, though they can tolerate partial shade.
Their trailing habit makes them a perfect spiller in containers, and they are self-cleaning, meaning they drop their old flowers to make way for new ones.
These low-maintenance annuals are also deer-resistant, making them a favorite among gardeners.
Light
Calibrachoa is a fast grower that thrives in full sun. This means they require at least six hours of full sun each day to produce their best blooms.
However, in hotter climates, these plants can tolerate partial shade, especially during the hottest part of the day.
The vibrant rainbow of colors, stripes, and speckle patterns that adorn the foliage of this prolific bloomer are best displayed under good sunlight.
Too much direct sunlight can lead to scorched leaves, so a balance between light and shade is essential for this South American genus.
Soil
Calibrachoa prospers best in well-drained soil rich in organic material. The plant is a heavy feeder, requiring a constant supply of nutrients throughout the growing season.
To ensure good drainage and prevent root rot, a common issue with this genus, incorporate some sand or perlite into the soil. Additionally, a slow-release fertilizer can be added to the soil at planting time to provide a steady stream of nutrients.
Calibrachoa also prefers slightly acidic soil, so gardeners may need to amend their soil accordingly.
Water
Calibrachoa requires frequent watering, especially during the growing season. However, it’s crucial to ensure good drainage to prevent root rot, a common problem with this genus.
Overwatering can lead to waterlogged soil and poor root health. A good rule of thumb is to water when the top inch of soil feels dry to the touch.
But remember, while they love a good drink, these plants also need good air circulation around their roots, so avoid letting them sit in water.
Temperature and Humidity
Calibrachoa loves warm temperatures. They are best suited to climates where temperatures do not drop below freezing, as frost can severely damage the plant.
They can tolerate a wide range of humidity levels, from dry to humid, as long as there is good air circulation to prevent conditions that can lead to root rot.
Fertilizer
Calibrachoa requires frequent fertilization during the growing season. A slow-release fertilizer works best, providing the plant with a steady supply of nutrients.
A water-soluble fertilizer can be used every two weeks instead. It’s important to avoid over-fertilization as this can lead to root rot due to poor drainage.
Types of Calibrachoa
- Calibrachoa ‘Cabaret Hot Pink’: The ‘Cabaret Hot Pink’ is a stunning variety of the calibrachoa genus, also known as million bells. This vibrant pink, trailing plant is perfect for hanging baskets and window boxes due to its compact size and trailing habit.
- Calibrachoa ‘Cabaret Purple Glow’: The ‘Cabaret Purple Glow’ calibrachoa is a spectacular annual that displays a rainbow of colors in its foliage. The leaves are speckled with a mix of purple and white hues, creating a stunning visual effect.
- Calibrachoa ‘Million Bells® Terra Cotta’: Introduced in the early 1990s, the ‘Million Bells® Terra Cotta’ is a hybrid calibrachoa known for its unique color and 10-inch-long stems.
- Calibrachoa ‘MiniFamous Double Blue’: The ‘MiniFamous Double Blue’ calibrachoa is a compact, trailing variety that produces double blooms in a striking blue shade. This variety is a short-lived perennial, usually grown as an annual, and is best suited for hanging baskets due to its trailing habit.
- Calibrachoa ‘Superbells® Pomegranate Punch’: The ‘Superbells®
Pomegranate Punch’ calibrachoa is a favorite for its vibrant, deep red flowers with black speckled throats.
- Calibrachoa ‘Kabloom’: The ‘Kabloom’ calibrachoa is the first seed-grown calibrachoa, offering a cost-effective way for gardeners to enjoy these beautiful plants.
How to Plant Calibrachoa From Seed
Step 1: Planting the Seeds
Calibrachoa seeds are tiny and need to be handled with care. They prefer a good drainage system to prevent root rot, a common problem with this species.
They should be planted in a mixture of soil and organic material, which provides the necessary nutrients for their growth.
Plant the seeds in garden beds or baskets, ensuring that they have at least 10-inch-long stems for the trailing plant to grow optimally. Remember, Calibrachoa is a heavy feeder, so a slow-release fertilizer should be added at the time of planting.
Step 2: Caring for the Seedlings
Once the seeds are planted, they require frequent watering but be careful not to overwater as this can lead to root rot. Calibrachoa plants need good air circulation, so make sure they are not overcrowded.
These plants are self-cleaning, meaning they drop their old flowers to make way for new ones, making them a low-maintenance choice for your garden. Despite this, it’s essential to monitor them for aphids, a common pest that can affect their health.
How to Propagate Calibrachoa
Step 1: Prepare the Planting Medium
Calibrachoa requires a planting medium rich in nutrients and organic material. It also needs good drainage to prevent root rot, a common issue with this plant. A mix of potting soil and perlite or sand can provide the necessary drainage.
Add a slow-release fertilizer to the mix to provide the necessary nutrients throughout the growing season.
Step 2: Propagate the Plant
Cut a 10-inch-long stem from the parent plant, ensuring it has several leaves. Remove the leaves from the bottom half of the stem.
The cuttings should then be placed in the prepared planting medium.
How to Pot or Repot Calibrachoa
Step 1: Selecting the Right Pot
The first step in potting or re-potting calibrachoa is selecting the right pot. A 10-inch-long stem is common, so choose a pot that allows for good air circulation and good drainage to prevent root rot.
Hanging baskets are a popular choice as they allow the plant’s trailing nature to shine.
Step 2: Preparing the Soil
Prepare a soil rich in organic material, ensuring it has good drainage to prevent water-logging. A slow-release fertilizer can be mixed into the soil at this stage to provide nutrients throughout the season.
Step 3: Planting the Calibrachoa
When planting your calibrachoa, whether it’s an annual or a short-lived perennial, make sure to plant it at the same depth it was growing previously.
Common Pests and Plant Diseases for Calibrachoa
Aphids
Aphids are common pests that can affect the calibrachoa. These tiny pests suck the nutrients from the plant, causing the leaves to curl and yellow.
They can also lead to a sooty mold fungus due to the sticky honeydew they excrete. Good air circulation and occasional spraying with water or insecticidal soap can help control aphids.
Root Rot
Root rot is a disease often caused by overwatering or poor drainage, which are conditions that the calibrachoa is particularly susceptible to. The roots become waterlogged and deprived of oxygen, leading to their decay.
Symptoms include wilting, yellowing foliage, and stunted growth. To prevent root rot, ensure your calibrachoa is planted in well-draining soil and avoid overwatering. A hanging basket or raised garden bed can provide good drainage conditions.
Deer
While calibrachoa is considered deer-resistant, hungry deer may still nibble on the leaves and flowers, particularly in areas where food is scarce.
This can result in uneven growth and fewer blooms. To deter deer, consider using deer repellents or installing a physical barrier like a fence.
Common Plant Problems and Solutions for Calibrachoa
Brown Tips
One common problem with the plant calibrachoa is the appearance of brown tips on its 10-inch-long stems. This issue is often a sign of root rot, a condition usually caused by overwatering and poor drainage.
To prevent this, ensure your calibrachoa is planted in a location with good drainage, such as garden beds or hanging baskets, and avoid frequent watering.
Yellowing Leaves
Yellowing leaves on your calibrachoa may indicate a nutrient deficiency, as this plant is a heavy feeder.
This fast grower requires a continuous supply of nutrients throughout the growing season, which can be provided by using a slow-release fertilizer or a water-soluble fertilizer.
Also, incorporating organic material into the soil can improve its nutrient content.
Frost Damage
Calibrachoa is sensitive to frost. Frost can damage the leaves and stems, hindering the plant’s continuous blooming.
To protect your calibrachoa from frost, consider moving your baskets and window boxes indoors during cold nights or covering your garden beds with a frost blanket.
Failure to Bloom
Calibrachoa is known for its best blooms in a rainbow of colors, stripes, and speckle patterns. However, if your plant is not blooming as expected, it may not be receiving enough light.
This trailing plant prefers at least six hours of full sun each day, although it can tolerate partial shade. If necessary, consider moving your plant to a sunnier location.
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