How to Grow Calibrachoa
Calibrachoa × hybrida
Calibrachoa (Million Bells) is a half-hardy trailing annual for full sun and free-draining, slightly acidic compost. Usually bought as plugs or young plants rather than grown from seed. Plant out after last frost into baskets, containers, or window boxes. Feed weekly with high-potash liquid fertiliser and water regularly — they dislike drying out but hate waterlogging. Self-cleaning so no deadheading needed. Trim back leggy growth mid-season for a fresh flush. Protect from frost; discard at season end.
When to Start
Sow indoors 7 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 12°C.
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Growth Stages
Approximate days from start
Care Essentials
- Liquid feed weekly with a high-potash fertiliser throughout the flowering season. Iron-hungry — use ericaceous feed if leaves yellow.
- Prolific bloomer from late spring to first frost. Self-cleaning — spent flowers drop naturally. Needs acidic compost (pH 5.5-6.0) and excellent drainage.
Growing Conditions
- Min. soil temperature
- 12°C+
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 25 cm |
| Mature height | 20 cm |
| Mature spread | 35 cm |
For trailing varieties in hanging baskets and containers. Space closer in mixed plantings for a full display.
Pests & Diseases
Pest Aphids
Identification: Clusters of small green insects on shoot tips, sticky honeydew, distorted new growth
- Blast off with a jet of water
- Soft soap spray
- Encourage ladybirds and hoverflies
- Pyrethrum-based contact insecticide
Pest Tobacco Budworm
Identification: Holes in flower buds, buds fail to open, small caterpillars inside damaged buds
- Hand-pick caterpillars at dusk
- Bacillus thuringiensis (Bt) spray
- Spinosad-based insecticide
Disease Iron Chlorosis Nutrient deficiency
Symptoms: Leaves turn yellow between veins while veins remain green, starting with youngest leaves. Growth slows.
Treatment: Apply sequestered iron or ericaceous feed. Water with rainwater instead of tap water.
Prevention: Use acidic compost (pH 5.5-6.0). Avoid alkaline tap water. Feed regularly with ericaceous fertiliser.
Disease Root Rot Pythium spp. / Phytophthora spp.
Symptoms: Wilting despite moist soil, brown mushy roots, plant collapse. Often starts at the base.
Treatment: Remove affected plants. Improve drainage. Allow compost to dry slightly between waterings.
Prevention: Use free-draining compost with added perlite. Never let pots sit in saucers of water. Ensure drainage holes are clear.
Growing Conditions
| Min. soil temperature | 12°C |
| Base growth temperature | 10°C |
| Min. daylength to start | 11h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Calibrachoa?
- Plant Calibrachoa 20cm apart with 25cm between rows.
- When does Calibrachoa flower?
- Calibrachoa typically flowers approximately 40 days after transplanting.
- Is Calibrachoa frost hardy?
- Calibrachoa is classified as Half Hardy.
