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How to Grow Antirrhinums

Antirrhinum majus

Half Hardy Cool Season Continuous Harvest

When to Start

Sow indoors 8 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 6°C.

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Growth Stages

Sow seeds
Germination ~14d
Flowering ~98d

Approximate days from start

Care Essentials

  • Feed every three to four weeks with a balanced liquid fertiliser once plants are established in their final position. Avoid high-nitrogen feeds which promote leaf growth over flowers.
  • Good air circulation is the single most important factor in preventing rust and mildew. Space plants well, water at the base, and choose rust-resistant varieties for trouble-free growing.

Companion Planting

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Growing Conditions

Min. soil temperature: 6°C+
Germination temperature: 18–22°C

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Spacing & Planting

Plant spacing 25 cm
Row spacing 30 cm
Sow depth 0 cm
Mature height 45 cm
Mature spread 25 cm

Also known as Snapdragons. Taller varieties may need slightly more space (30 cm) and support. Closer spacing encourages taller stems for cutting.

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Care Guide

Feeding
Feed every three to four weeks with a balanced liquid fertiliser once plants are established in their final position. Avoid high-nitrogen feeds which promote leaf growth over flowers.
Watch for
  • Antirrhinum rust (Puccinia antirrhini)
  • Downy mildew
  • Grey mould (Botrytis)
  • Aphids on shoot tips
  • Capsid bug damage

Pests & Diseases

Pest Aphids

Identification: Clusters of green, black, or pink aphids on growing tips and flower spikes. Sticky honeydew and distorted buds.

Organic treatment:
  • Blast off with a strong jet of water
  • Spray with insecticidal soap
  • Encourage ladybirds, lacewings, and hoverflies
Chemical treatment:
  • Spray with a pyrethrin-based insecticide if heavy infestations persist
Pest Capsid Bugs

Identification: Ragged holes and distorted shoot tips. Flower buds may be blind or misshapen. Damage appears before the pest is seen as capsids are fast-moving.

Organic treatment:
  • Keep beds weed-free to reduce overwintering sites
  • Tolerate minor damage — plants usually grow through it
Chemical treatment:
  • Spray with a contact insecticide in the evening when bugs are less active
Pest Slugs and Snails

Identification: Irregular holes in leaves and stems. Slime trails on foliage. Seedlings can be eaten to ground level overnight.

Organic treatment:
  • Apply organic slug pellets (ferric phosphate) around transplants
  • Use copper tape or beer traps
  • Encourage natural predators
Chemical treatment:
  • Apply ferric phosphate slug pellets around plants
Disease Antirrhinum Rust Puccinia antirrhini

Symptoms: Dark brown or chocolate-coloured powdery pustules on leaf undersides, stems, and calyces. Upper leaf surfaces show pale spots. Severe infections cause leaf drop and plant death.

Treatment: Remove and destroy affected leaves and plants immediately. Do not compost. Clear all plant debris at the end of the season.

Prevention: Choose rust-resistant varieties (e.g., Rocket, Madame Butterfly series). Space plants well for airflow. Water at the base, not overhead. Rotate planting positions annually.

Disease Downy Mildew Peronospora antirrhini

Symptoms: Pale yellow patches on upper leaf surfaces with grey-purple fuzzy growth underneath. Leaves curl and brown.

Treatment: Remove affected leaves. Improve air circulation. Destroy badly affected plants.

Prevention: Space plants well. Water at the base. Avoid overcrowding. Ensure good ventilation in greenhouses.

Disease Grey Mould Botrytis cinerea

Symptoms: Fuzzy grey fungal growth on flowers, stems, and leaves. Affected tissue turns brown and rots. Often starts on spent flowers.

Treatment: Remove and destroy affected material promptly. Improve air circulation.

Prevention: Deadhead regularly. Avoid overhead watering. Space plants well. Remove debris from around plants.

Growing Conditions

Min. soil temperature6°C
Germination temperature18–22°C
Base growth temperature6°C
Min. daylength to start9.5h
Photoperiod sensitivitylong day

Frequently Asked Questions

How far apart should I plant Antirrhinums?
Plant Antirrhinums 25cm apart with 30cm between rows.
When does Antirrhinums flower?
Antirrhinums typically flowers approximately 65 days after transplanting.
Is Antirrhinums frost hardy?
Antirrhinums is classified as Half Hardy.

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