Fertilising guide
How to fertilise Million bells (Calibrachoa × hybrida)— schedule & NPK
Also called Million bells, Mini petunia, Trailing petunia.
More about million bells
About Million bells
Calibrachoa × hybrida · also called Million bells, Mini petunia · flowering
Million bells is a prolific trailing annual producing hundreds of small petunia-like flowers in a vast range of colours from spring through autumn frost. Self-cleaning and vigorous, it excels in hanging baskets, window boxes, and container edges. It demands excellent drainage, regular feeding, and full sun to maintain its non-stop floral display.
Growth habit: Trailing, mounding annual; highly branched, self-cleaning
Watch for — Iron/magnesium chlorosis (yellowing between veins): The most common issue; caused by pH above 6.2, waterlogged roots, or insufficient feeding. Lower pH with ericaceous feed, improve drainage, and apply iron chelate or Epsom salt (magnesium sulphate) foliar spray.
What fertiliser million bells actually wants — and why
Million bells is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for million bells: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed million bells, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For million bells:
Feed weekly with a high-potassium, iron-supplemented liquid fertiliser formulated for petunias or calibrachoa. A slow-release fertiliser incorporated at planting can be supplemented with liquid feeding. Iron chelate supplementation resolves yellowing if the soil pH drifts above 6.2. Treat that as weekly between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when million bells is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for million bells
Half strength is the safe default for million bells — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water million bells first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the million bells watering schedule.
Signs you are over-feeding million bells
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for million bells:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding million bells
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full million bells care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of million bells with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for million bells
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising million bells — frequently asked questions
What fertiliser does million bells need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Million bells is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed million bells?
Feed weekly with a high-potassium, iron-supplemented liquid fertiliser formulated for petunias or calibrachoa. A slow-release fertiliser incorporated at planting can be supplemented with liquid feeding. Iron chelate supplementation resolves yellowing if the soil pH drifts above 6.2. Feed weekly with a high-potassium, iron-supplemented liquid fertiliser formulated for petunias or calibrachoa. A slow-release fertiliser incorporated at planting can be supplemented with liquid feeding. Iron chelate supplementation resolves yellowing if the soil pH drifts above 6.2. Treat that as weekly between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for million bells?
Half strength is the safe default for million bells — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding million bells look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding million bells year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of million bells?
Flush the pot of million bells with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Million bells care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water million bells — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise amelanchier canadensis
- How to fertilise amelanchier × grandiflora 'robin hill'
- How to fertilise sorbus aria
- All 6887 fertilising guides in the Growli library