How to Grow Geranium
Pelargonium × hortorum
Commonly grown “geraniums” are pelargoniums—tender perennials best in full sun, free-draining compost, and sheltered sites. Start or buy young plants in spring, pinch to bush, and deadhead to keep blooms coming. Water thoroughly then allow the surface to dry slightly; avoid waterlogged compost. Feed regularly in containers. Before frost, take cuttings or move plants under cover to overwinter bright and cool. Avoid hard pruning into old, woody stems until new growth is active.
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.
Growing Conditions
- Min. soil temperature
- 12°C+
- Germination temperature
- 21–24°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- 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.
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.
