How to Grow Geranium
Pelargonium × hortorum
When to Start
Start seeds indoors 9 weeks before your last frost date. Transplant outdoors once night temperatures stay above 8°C and soil has warmed to at least 12°C.
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Growth Stages
Approximate days from start
Care Essentials
- Balanced liquid feed fortnightly during the growing season.
- Bedding geraniums are actually pelargoniums. Take cuttings in late summer for next year's plants.
Companion Planting
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Growing Conditions
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- Sow indoors
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- Transplant out
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- First harvest
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Spacing & Planting
| Plant spacing | 30 cm |
| Row spacing | 45 cm |
| Sow depth | 0 cm |
| Mature height | 45 cm |
| Mature spread | 45 cm |
Refers to Zonal Geraniums (Pelargoniums). Hardy perennial Geraniums (Cranesbills) have varied spacing based on species, from 30 cm to 90 cm.
Care Guide
- Feeding
- Balanced liquid feed fortnightly during the growing season.
- Watch for
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- Vine weevil
- Whitefly
- Rust
- Grey mould
Pests & Diseases
Pest Vine Weevil
Identification: Adults notch leaf edges; white C-shaped larvae in compost eat roots, causing sudden wilting and plant collapse
- Apply biological control nematodes (Steinernema kraussei) to compost in spring or autumn when soil is above 5°C
- Check root balls when repotting and remove any larvae found
- Encourage ground beetles which eat vine weevil eggs
- Use a compost drench containing acetamiprid for container plants
Pest Glasshouse Whitefly
Identification: Tiny white-winged insects fly up when plants are disturbed; sticky honeydew and sooty mould on leaves
- Hang yellow sticky traps among plants to monitor and reduce numbers
- Introduce the parasitic wasp Encarsia formosa as biological control under glass
- Spray with a fatty acid or plant oil-based insecticide
Pest Geranium Budworm
Identification: Small caterpillars bore into flower buds and developing blooms, causing buds to fail to open or flowers to be ragged
- Pick off caterpillars by hand
- Remove and destroy affected buds
- Spray with a contact insecticide containing deltamethrin if infestation is severe
Disease Pelargonium Rust Puccinia pelargonii-zonalis
Symptoms: Concentric rings of brown pustules on the undersides of leaves with corresponding yellow spots on upper surfaces
Treatment: Remove and destroy affected leaves immediately. Improve air circulation around plants
Prevention: Space plants well, avoid overhead watering, and inspect new plants carefully before introducing them
Disease Grey Mould (Botrytis) Botrytis cinerea
Symptoms: Fuzzy grey mould on leaves, stems and flowers, often starting on dead or damaged tissue
Treatment: Remove affected parts promptly. Improve ventilation and reduce humidity around plants
Prevention: Avoid overcrowding, remove dead flowers and leaves promptly, and water at soil level
Disease Blackleg
Symptoms: Black, water-soaked rot at the base of stems, causing cuttings or young plants to collapse
Treatment: Remove and destroy affected plants. Use clean, sterile compost and containers for cuttings
Prevention: Take cuttings with a clean, sharp blade, allow cut surfaces to dry before inserting, and avoid overwatering
Growing Conditions
| Min. soil temperature | 12°C |
| Germination temperature | 21–24°C |
| Base growth temperature | 8°C |
| Min. daylength to start | 11h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Geranium?
- Plant Geranium 30cm apart with 45cm between rows.
- When does Geranium flower?
- Geranium typically flowers approximately 75 days after transplanting.
- Is Geranium frost hardy?
- Geranium is classified as Tender.
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