Ornamental · Solanaceae
Calibrachoa
Calibrachoa × hybrida
Give it full sun, steady water, and acidic soil, and calibrachoa will pour bloom from spring all the way to frost.
Full sun
Every 1–3 days
USDA 9–11
3–12 in · 8–30 cm
Overview
If you have ever admired a basket dripping with tiny petunia-style flowers, you have met calibrachoa, the plant nearly everyone calls Million Bells. It trails its small blooms over the rim of a pot or basket through the whole season. As a member of the nightshade family, it is a near cousin of the petunia, yet it earns its own name fairly. The blooms come smaller, the form leans more mounding and trailing, and the colors run richer.
Across most of the country, gardeners treat it as a warm-season annual, because it is a tender perennial that only lives through winter in the gentlest zones. It thrives on heat and sun, frees you from any deadheading, and keeps blooming without a break. That blend of easygoing toughness and steady color is exactly why it fills so many summer containers.
In return, the plant asks for just a few things, and they are all manageable. It is a hungry, thirsty grower that prefers slightly acidic soil and reliable moisture, and it pouts in shade. Sort out the sun, the feeding, and the soil pH, and you will find the rest looks after itself.
Care
The short version: full sun, steady moisture in a pot that drains fast, and a slightly acidic mix you feed every couple of weeks. Pinch the tips now and then to keep it bushy, and forget about deadheading altogether.
Light
Calibrachoa is happiest in full sun, 8 or more hours a day. Bloom thins out quickly the more shade it gets, so a spot that soaks up afternoon light rewards you with the fullest, most colorful plant.
Water
Aim to keep the mix evenly moist but never soggy. Through summer heat, baskets and pots can want water daily, sometimes more, as the surface dries within a day or two. Always grow in a pot with drainage holes, since standing water is what opens the door to root rot.
Soil
Plant it in a well-draining, organically rich potting mix that leans acidic, somewhere around pH 5.0 to 6.5. A peat-based mix suits it nicely. Steer clear of heavy clay in beds, which holds far too much water for these roots.
Temperature
It copes with a broad range, from about 41°F to 95°F (5°C to 35°C), and takes summer heat without complaint. Frost is its one hard limit, which is why most gardeners simply grow it as an annual.
Humidity
Ordinary humidity of 40% to 60% keeps it content, so this is not a plant to fuss over there. Good airflow around crowded baskets helps it far more than any number on a gauge.
Feeding
Expect a heavy feeder. Blend a slow-release balanced fertilizer into the mix at planting, then follow up with a dilute water-soluble balanced feed every other week. Should the new growth yellow, work in some chelated iron or iron sulfate to set it right.
Pruning
Here is a chore you can cross off: there is no deadheading to do, since spent flowers drop by themselves. Just pinch the stem tips back about 2 in (5 cm) at planting or midseason to keep the plant compact and coax fresh branching and bloom.
Repotting
You will not really repot calibrachoa. It is grown as a single-season container plant and swapped out each spring, so once it settles into its pot or basket it simply stays put for the year.
Size & spacing
Plants stay low and wide, roughly 3 to 12 inches (8 to 30 cm) tall with a trailing reach of 12 to 24 inches (30 to 60 cm). That mounding, cascading shape is just what lets them spill so gracefully over a basket edge.
When to plant
Calibrachoa lives for warmth and cannot stand frost, so timing is simple and forgiving. Set your plants out in spring once the chill has gone and the soil has warmed past 55°F (13°C), and they will keep blooming from late spring until the first frost closes the season.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring, after the last frost once soil temperatures exceed 55°F (13°C)
- Harvest: late spring continuously until first frost
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Nearly every calibrachoa hiccup comes back to soil pH, watering, or light, and the plant tells you through its leaves and its flowering. Catch the early hints and you can turn things around before they slide further. Find your symptom below, then act while it still does some good.
It droops in soggy soil and gives way at the base
A plant that flops while the mix stays wet is usually fighting root or stem rot from Pythium or Phytophthora. Gently lift it from the pot and study the roots: the good ones are pale and firm, while rotted ones turn brown, mushy, and thin out. A plant that far gone cannot be rescued, so toss it without guilt and tuck any healthy survivors into fresh, fast-draining mix in a pot that drains properly.
Fix:
- Stop watering until the top of the mix dries
- Remove and discard badly affected plants
- Replant survivors in fresh, fast-draining mix in a container with working drainage holes
The youngest leaves go yellow but their veins stay green
Take heart, because this is a familiar fix. You are looking at iron deficiency, and it appears on the freshest leaves first because calibrachoa wants more iron than the average bedding flower. Most of the time the trouble starts when the mix creeps past pH 6.5, which traps iron out of reach of the roots. Test your mix, nudge the pH back down to 5.5 to 6.0 with iron sulfate, then drench with chelated iron and watch the new leaves turn green again.
Fix:
- Lower the media pH toward 5.5 to 6.0 using iron sulfate per label directions
- Drench with chelated iron to green up new growth
- Resume feeding every other week with a balanced water-soluble fertilizer
Sticky leaves, speckled foliage, or warped fresh shoots
Signs like these point to aphids, thrips, or spider mites, the trio you are most likely to meet on calibrachoa. Look over the shoot tips and the undersides of leaves for huddled aphids, faint webbing, or thin thrips that scatter when you knock a stem over a sheet of white paper. The good part is they are easy to manage: a firm blast of water clears most of them, and insecticidal soap or horticultural oil mops up whatever lingers.
Fix:
- Knock pests off with a strong spray of water
- Treat infestations with insecticidal soap or horticultural oil per label
- Discard heavily infested stems
Thin on flowers with long, reaching stems
When a plant turns leggy and quits blooming, not enough sun is almost always behind it, because flowering tapers off the shadier the spot gets. Skimpy feeding piles on, since this hungry plant runs low on fuel without regular meals. Shift the container into full sun, snip the stretched tips back about 2 in (5 cm) to wake up fresh branching, and feed every other week. It bounces back kindly.
Fix:
- Move containers to a spot with full sun
- Trim back leggy stem tips by about 2 in (5 cm) to force branching
- Feed every other week with a balanced water-soluble fertilizer
Toxicity
Here is reassuring news for pet owners and parents: calibrachoa is safe to have all around the home. It is missing from the ASPCA toxic plant lists, and its close cousin the petunia is listed as non-toxic. The worst a curious nibble might bring is a mild, fleeting stomach upset, the kind nearly any plant can cause.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax with cats around it. The plant stays off the ASPCA toxic list, and the most a nosy nibble brings is the occasional mild tummy upset that almost any greenery can cause.
Dogs None
Dogs are in the clear too. A pup that gnaws a trailing stem might get a passing stomach grumble from the fiber, but there is no toxin to worry about.
Horses Safe
Horses can graze beside it without coming to harm. Nothing in the plant is known to poison them.
Rabbits Safe
Rabbits have nothing to fear from the leaves or flowers, and a stem or two does no more than fill a little belly.
Livestock Safe
Cattle, goats, and sheep can share space with it safely, since it holds no compounds that bother grazing animals.
Birds Safe
Pet and garden birds are perfectly fine near the blooms. There is no need to screen the baskets away from them.
People Safe
It is harmless to people, though it is grown for looks rather than the table. Children playing close by face no danger from it.
No special handling precautions are needed
Varieties
Calibrachoa comes to gardeners as a small set of named series rather than as single varieties. Here are the ones it pays to know by name.
Million Bells
The first trademarked series, it brought calibrachoa to gardeners across the US back in the 1990s and lent the plant the everyday name people still use.
Superbells
A strong-trailing series in solid, double, and patterned shades that performs well year after year in university trials.
MiniFamous
A series prized for its double blooms, including forms like Uno Yellow and Uno Pink Star that extension horticulturists point to.
Cabaret
A tidy, even-growing series made for hanging baskets and mixed pots, and it scores well in extension trials.
Callie
A semi-trailing series that carries the plant's extension nickname callie and keeps baskets blooming the whole season through.
How to propagate
Calibrachoa is grown from cuttings rather than seed, though patents place real limits on trying it yourself.
Stem cuttingsModerate
Spring to summer
Cuttings are the realistic way to grow more calibrachoa, because the plants make so little seed. Take them from healthy growing stems in spring or summer. One thing to keep in mind: most named cultivars are patented, so propagating them at home is off the table legally.
Myths
You have to deadhead calibrachoa the way you would a petunia to keep the flowers coming.
Happily, the flowers tidy themselves, so faded blooms simply fall away on their own. There is no need to pinch a single one off to keep the color rolling. It flowers from spring right up to frost with zero deadheading.
Calibrachoa is really just a tiny petunia you can raise from seed you saved yourself.
It is a genus all its own rather than a shrunken petunia, and it makes hardly any seed. Almost every garden hybrid comes from cuttings instead. Most cultivars are patented, which means home propagation is not allowed.
If calibrachoa leaves turn yellow, it always means you have overwatered it.
When the yellowing lands on new growth and the veins stay green, the real culprit is usually iron deficiency from a media pH that has climbed too high. This plant asks for more iron than most bedding flowers and thrives in a slightly acidic mix near pH 6.0.