Ornamental · Solanaceae
Calibrachoa
Calibrachoa × hybrida
Give it full sun, steady water, and acidic soil, and calibrachoa pours out bloom from spring right to frost.
Full sun
Every 1–3 days
USDA 9–11
3–12 in · 8–30 cm
Overview
Most folks know calibrachoa as Million Bells, the trailing flower that spills little petunia-style blooms over the rim of a pot or basket all summer long. It's part of the nightshade family and a close relative of the petunia, yet it earns its own name fair and square. The blooms run smaller, the shape is more mounding and trailing, and the colors go richer.
In most of the country you'll grow it as a warm-season annual, since it's a tender perennial that only sticks around over winter in the mildest spots. It thrives on heat and sun, saves you the chore of deadheading, and just keeps flowering. That blend of being tough and endlessly colorful is why it shows up in so many summer containers.
It does want a couple of favors in return, though. It's a hungry, thirsty plant that likes slightly acidic soil and reliable moisture, and it pouts in the shade. Nail the sun, the feeding, and the soil pH, and honestly the rest sorts itself out.
Care
The short version: full sun, steady moisture in a fast-draining pot, and a slightly acidic mix that gets fed every couple of weeks. Pinch the tips here and there to keep it bushy, and forget about deadheading completely.
Light
Calibrachoa is after full sun, 8 or more hours a day. Bloom drops off quickly as the shade grows, so a spot that soaks up afternoon light gives you the fullest, most colorful plant you can get.
Water
Keep the mix evenly moist but never soggy. When summer heats up, baskets and pots can want a drink every single day, sometimes more, while the top dries out within a day or two. Always plant in a pot with drainage holes, since sitting in wet is exactly what brings on 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 is a good match. Steer clear of heavy clay in beds, which holds way too much water for these roots.
Temperature
It copes with a big range, roughly 41°F to 95°F (5°C to 35°C), and takes summer heat without complaint. Frost is the dealbreaker, which is why most gardeners just grow it as an annual.
Humidity
Average humidity of 40% to 60% keeps it content, so this isn't a plant you'll fret over on that score. Decent airflow around packed baskets does far more than any number on a gauge ever will.
Feeding
This one's a heavy feeder. Stir a slow-release balanced fertilizer into the mix at planting, then keep up with a dilute water-soluble balanced feed every other week. If the new growth starts yellowing, mix in some chelated iron or iron sulfate to bring the color back.
Pruning
There's no deadheading at all, since the old flowers fall off on their own. Just pinch the stem tips back about 2 in (5 cm) at planting or midseason to keep things compact and spur fresh branching and bloom.
Repotting
Calibrachoa doesn't really get repotted. You grow it as a single-season container plant and swap it out each spring, so once it's settled in its pot or basket it stays put for the year.
Size & spacing
Plants keep low and spreading, around 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 habit is exactly what lets them tumble so nicely over a basket's edge.
When to plant
Calibrachoa lives for warmth and won't put up with frost at all. Plant it out in spring once the cold has cleared and the soil has warmed past 55°F (13°C), and it'll flower from late spring all the way until the first frost calls it quits.
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
Just about every calibrachoa hiccup comes back to soil pH, watering, or light, and it shows up in the leaves and the bloom. Catch the early clues and you can save a plant before it slides too far. Find the match below, then step in while it still does some good.
Wilting in soggy soil, then a collapse at the base
A plant that flops even though the mix is sopping wet is usually fighting root or stem rot from Pythium or Phytophthora. Pop it out of the pot and take a look at the roots. The good ones are white and firm, and the rotted ones are brown, mushy, and thin on the ground. A plant that far gone can't be rescued, so toss it and move any healthy survivors into fresh, fast-draining mix and 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
Newest leaves go yellow but the veins stay green
What you're seeing is iron deficiency, and it shows on the freshest leaves first because calibrachoa is a greedy feeder that wants more iron than your average bedding flower. Usually the mix has crept above pH 6.5, which ties the iron up so the roots can't get at it. So test the mix, nudge the pH back toward 5.5 to 6.0 with iron sulfate, and pour on some chelated iron to green those new leaves up 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 new shoots
Those are the giveaways of aphids, thrips, or spider mites, the trio that bugs calibrachoa most often. Take a close look at the shoot tips and the undersides of leaves for clumps of aphids, fine webbing, or skinny thrips that go flying when you tap a stem over a sheet of white paper. A hard blast from the hose knocks most of them loose, and insecticidal soap or horticultural oil mops up whatever's left.
Fix:
- Knock pests off with a strong spray of water
- Treat infestations with insecticidal soap or horticultural oil per label
- Discard heavily infested stems
Hardly any flowers and long, reaching stems
Not enough sun is the usual culprit when a plant stretches out and quits blooming, since the flowers fade away as the shade deepens. Skimping on food makes things worse, because this is a heavy eater that runs out of gas without regular meals. Shift the container into full sun, snip the leggy tips back about 2 in (5 cm) to wake up fresh branching, and feed it 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
Here's the reassuring part for pet owners and parents: calibrachoa is safe to grow around the whole household. It's not on the ASPCA toxic plant lists, and its close cousin the petunia is listed as non-toxic. The most a curious nibble might do is cause a mild, short-lived stomach upset, the sort any plant can trigger.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are fine around it. The plant never made the ASPCA toxic list, and the worst a nosy nibble does is the kind of mild tummy upset that almost any plant can hand out.
Dogs None
Dogs are in the clear too. A pup that chews on a trailing stem might get a quick gurgle from all the fiber, but there's no actual toxin in play here.
Horses Safe
Horses can graze right beside it with no trouble. Nothing in the plant is known to poison them.
Rabbits Safe
Rabbits have nothing to fear from the leaves or flowers, and a couple of stems will only fill them up a bit.
Livestock Safe
Cattle, goats, and sheep can hang around it safely, since the plant carries no compounds that bother grazing animals.
Birds Safe
Pet and backyard birds are perfectly fine near the blooms. No need to wall the baskets off from them.
People Safe
It's harmless to people, though keep in mind it's an ornamental and not something you'd eat. Kids playing close by are in no danger from it.
No special handling precautions are needed
Varieties
Calibrachoa comes to gardeners as a handful of named series rather than stand-alone varieties. Here are the ones worth knowing by name.
Million Bells
The first trademarked series, the one that brought calibrachoa to US gardeners back in the 1990s and handed the plant the common name everybody still uses.
Superbells
A strong trailing series with solid, double, and patterned colors that performs reliably in university trials.
MiniFamous
A series prized for its double-flowered types like Uno Yellow and Uno Pink Star that extension horticulturists point to.
Cabaret
A tidy, even series that fits hanging baskets and mixed pots nicely and scores well in extension trials.
Callie
A semi-trailing series that lends the plant its extension nickname callie and keeps baskets in bloom right through the season.
How to propagate
Calibrachoa is grown from cuttings instead of seed, though patents really do limit how much of that you can do yourself.
Stem cuttingsModerate
Spring to summer
Cuttings are really the only practical way to make more calibrachoa, since the plants barely set any seed. Take yours in spring or summer from strong, healthy stems. Here's the catch though: most named cultivars are patented, which means propagating them at home isn't legal.
Myths
You have to deadhead calibrachoa like a petunia or it'll stop blooming.
Not so, because the flowers are self-cleaning and spent blooms simply drop off by themselves. There's no pinching required to keep the show running. It blooms from spring until frost with no deadheading at all.
Calibrachoa is just a tiny petunia you can grow from saved seed.
It's actually its own genus, not a mini petunia, and it makes very few seeds. Almost every garden hybrid comes from cuttings instead. Most cultivars are patented, so propagating them at home is off limits.
Yellow leaves on calibrachoa always mean you're overwatering.
When the yellow shows up on new growth and the veins stay green, the real cause is usually iron deficiency from a media pH that has climbed too high. This plant wants more iron than most bedding flowers and is happiest in a slightly acidic mix around pH 6.0.