Ornamental · Solanaceae
Calibrachoa
Calibrachoa × hybrida
Give it full sun, steady water, and acidic soil, and calibrachoa spills color over the edge from spring to frost.
Full sun
Every 1–3 days
USDA 9–11
3–12 in · 8–30 cm
Overview
Most people meet calibrachoa as Million Bells, the trailing flower that pours small petunia-shaped blooms over the rim of a pot or basket through the whole season. It sits in the nightshade family, a close relation of the petunia, yet it goes by its own name with good cause. The flowers come smaller, the habit leans more mounding and trailing, and the palette runs richer, which makes it a natural for a porch rail or a sunny window box.
Across most of the country gardeners treat it as a warm-season annual, a tender perennial that only winters over in the mildest zones. It thrives on heat and light, asks nothing in the way of deadheading, and keeps the color coming without a break. That blend of resilience and steady bloom is what earns it a place in so many summer arrangements, from a single statement basket to a clustered grouping on the steps.
It does set a few terms for the show. This is a hungry, thirsty feeder that wants slightly acidic soil and even moisture, and it loses heart in shade. Settle the sun, the feeding, and the soil pH, and the plant carries the styling on its own through the season.
Care
The short version: a sunny spot, even moisture in a fast-draining pot, and a slightly acidic mix fed every couple of weeks. Pinch the tips here and there to keep the shape full, and leave the deadheading off your list entirely.
Light
Calibrachoa wants full sun, 8 or more hours a day. Bloom thins quickly as shade takes over, so a place that catches strong afternoon light gives you the fullest, most colorful plant for a sunny corner.
Water
Keep the mix evenly moist but never soggy. Through summer heat, baskets and pots can call for water daily, sometimes more, while the surface dries within a day or two. Always set it in a pot with drainage holes, because standing wet is what opens the door to root rot.
Soil
Plant it in a well-draining, organically rich potting mix on the acidic side, somewhere around pH 5.0 to 6.5. A peat-based mix suits it nicely. Pass over heavy clay in beds, which traps more water than these roots can handle.
Temperature
It takes a broad range, from about 41°F to 95°F (5°C to 35°C), and shrugs off summer heat. Frost is the firm limit, which is why most gardeners run it as an annual.
Humidity
Ordinary indoor and outdoor humidity of 40% to 60% keeps it content, so it is not a plant to fuss over on that score. Good airflow around a crowded basket earns more than any number on a gauge.
Feeding
This is a heavy feeder. Work a slow-release balanced fertilizer into the mix at planting, then follow with a dilute water-soluble balanced feed every other week. If the new growth pales, add some chelated iron or iron sulfate to set it right.
Pruning
There is no deadheading to bother with, since the spent flowers fall on their own. Pinch the stem tips back about 2 in (5 cm) at planting or midseason to keep the plant compact and draw out fresh branching and bloom.
Repotting
Calibrachoa is not really repotted. It runs as a single-season container plant and gets replaced each spring, so once it is settled in its pot or basket it stays put for the year.
Size & spacing
Plants stay low and spreading, about 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 exactly what lets them drape so handsomely over the lip of a basket.
When to plant
Calibrachoa lives for warmth and will not stand a frost. Place it out in spring once the cold has lifted and the soil has warmed past 55°F (13°C), and it carries the display from late spring right through until the first frost calls time on 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
Almost every calibrachoa misstep comes back to soil pH, watering, or light, and the leaves and the bloom tell the story first. Catch the early signals and you can steer a plant back before the look slips. Find your match below, then act while the move still counts.
The plant slumps in soaked soil and gives way at the crown
When a plant flops while the mix is still drenched, point the finger at root or stem rot from Pythium or Phytophthora. Tip it out of the container and read the roots; the healthy ones run white and firm, the ruined ones turn brown, mushy, and sparse. A plant that far gone will not recover, so retire it and move any survivors into fresh, fast-draining mix in a pot that drains for real.
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
Fresh top growth pales to yellow while the veins hold their green
This look is iron deficiency, and it announces itself on the youngest shoots first because calibrachoa runs through more iron than the average basket filler. The culprit is usually a mix whose pH has crept past 6.5, which keeps the iron sitting out of reach of the roots. Test the mix, ease the pH back toward 5.5 to 6.0 with iron sulfate, and follow with a chelated iron drench to bring the color home.
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
A sticky film, mottled leaves, or warped new shoots
These are the tells of aphids, thrips, or spider mites, the trio that visits calibrachoa most. Look over the shoot tips and the leaf undersides for huddled aphids, faint webbing, or narrow thrips that scatter when you rap a stem above a sheet of white paper. A firm jet from the hose 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 bloom and long, reaching stems
Too little sun is the usual reason a plant stretches and quits flowering, since the bloom thins as shade gains ground. Skimpy feeding compounds it, because this is a hungry plant that stalls without regular meals. Shift the container into full sun, take the leggy tips back about 2 in (5 cm) to spark new branching, and feed every other week.
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
Welcome news for households with pets and children: calibrachoa is a safe choice to keep within reach. It stays off the ASPCA toxic plant lists, and its close cousin the petunia is listed as non-toxic. The most a curious taste might bring is a mild, passing stomach upset, the sort any plant can set off.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
An easy houseguest where cats roam. The plant skips the ASPCA toxic list, and a stray nibble brings nothing past the occasional mild upset that any greenery can stir.
Dogs None
Just as relaxed around dogs. One that gnaws a trailing stem may feel a passing grumble from the fiber, but no toxin is in play.
Horses Safe
Horses can pass the time beside it without trouble. Nothing in the plant is known to harm them.
Rabbits Safe
Rabbits take no harm from the leaves or flowers, and a few stems do little more than top them up.
Livestock Safe
Cattle, goats, and sheep can share the space safely, as the plant holds no compounds that bother grazers.
Birds Safe
Pet and garden birds sit happily near the blooms. No need to screen the baskets from them.
People Safe
Harmless to people, though it earns its place for looks rather than the table. Children at play nearby are in no danger from it.
No special handling precautions are needed
Varieties
Calibrachoa comes to gardeners through a short list of named series rather than stand-alone varieties. These are the ones worth recognizing by name when you shop.
Million Bells
The first trademarked series, the one that brought calibrachoa to American gardens in the 1990s and lent the plant the household name it still answers to.
Superbells
A strong trailing series running through solid, double, and patterned colors that keeps its form through university trials.
MiniFamous
A series prized for its double-flowered types, among them Uno Yellow and Uno Pink Star, that extension horticulturists call out.
Cabaret
A tidy, even series made for hanging baskets and mixed containers, and a reliable performer in extension trials.
Callie
A semi-trailing series that lends its name to the plant's extension nickname callie and keeps baskets in flower all season.
How to propagate
Calibrachoa is grown on from cuttings rather than seed, though patents put firm limits on trying it at home.
Stem cuttingsModerate
Spring to summer
Cuttings are the sensible route to more calibrachoa, since the plant sets so little seed. Take them through spring or summer from sound, growing stems. The catch to keep in mind: most named cultivars carry patents, so propagating them at home crosses a legal line.
Myths
You have to pluck the spent blooms off calibrachoa the way you do with petunias to keep it going.
The flowers clean up after themselves, so finished blooms simply fall away. There is no pinching to keep the display alive. It carries on flowering from spring to frost with no deadheading whatsoever.
Calibrachoa is really just a small petunia you can raise from seed you saved last year.
It stands as its own genus, not a shrunken petunia, and it sets barely any seed. Almost every garden hybrid comes from cuttings instead. Most cultivars carry patents, which puts home propagation off the table.
Yellow leaves on calibrachoa are always a sign you have watered it too much.
When the yellow shows on new growth and the veins stay green, the trouble is usually iron deficiency from a media pH that has climbed too high. This plant calls for more iron than most bedding flowers and prefers a slightly acidic mix near pH 6.0.