Snapdragon

Antirrhinum majus is native to the Mediterranean region, spanning from southern Portugal and Spain through to Morocco and Algeria. It thrives in rocky, well-drained habitats such as stone walls, rocky slopes, and old masonry.

• Natural range includes the western Mediterranean basin
• Has been cultivated in European gardens since at least the 15th century
• Became a model organism in genetics research due to its well-characterized flower-color and flower-shape mutations
• The classic 'deformed' (def) flower mutant was one of the first genes to be cloned in plants

Genetic significance:
• Gregor Mendel's laws of inheritance were later confirmed using Antirrhinum in early 20th-century studies
• The mutable aurea mutant, in which somatic transposition of the Tam3 transposon causes variegation, was the first plant transposon characterized at the molecular level (1980s)
• Snapdragon genetics helped establish the ABC model of flower development alongside Arabidopsis and other model species

Antirrhinum majus is a short-lived perennial typically grown as an annual or biennial, reaching heights of 15 to 100 cm depending on cultivar.

Stems & Foliage:
• Stems are erect, often branching, and slightly sticky due to glandular hairs
• Leaves are lanceolate to oblong, 1–7 cm long, arranged alternately or spirally on the stem
• Lower leaves may be opposite; leaf margins are entire; color is medium to dark green

Flowers:
• Bilateral (zygomorphic) tubular flowers, 3–4.5 cm long, with two-lipped corolla
• The upper lip is hooded; the lower lip has a prominent palate that closes the throat, requiring strong pollinators to force entry
• Flower colors include white, yellow, pink, orange, red, magenta, and bicolor combinations
• Flowers are arranged in dense, showy terminal racemes up to 30 cm long

Fruit & Seeds:
• Fruit is an ovoid capsule (~1 cm long) that opens by three pores at the top when mature
• Each capsule contains numerous tiny, dark brown to black seeds
• Individual seeds are approximately 0.6–0.8 mm long
• A single plant can produce thousands of seeds per season

Snapdragons occupy a range of open, sunny habitats in their natural Mediterranean environment, and perform best in cool to moderate temperatures in cultivation.

Preferred Conditions:
• Full sun to light partial shade
• Well-drained, moderately fertile soil with a neutral to slightly alkaline pH (6.5–7.5)
• Tolerant of poor, rocky, and sandy soils

Pollination Ecology:
• Primarily pollinated by bumblebees (Bombus spp.), which are strong enough to pry open the closed corolla
• Smaller bees and other insects generally cannot access the nectar and pollen
• This specialized pollination syndrome is an example of the 'buzz pollination' and 'bee strength' filtering strategy
• Self-incompatible in many cultivars due to a gametophytic self-incompatibility system, promoting outcrossing

Temperature Sensitivity:
• Prefers cool weather; optimal growing temperature range is 15–24°C (60–75°F)
• Performs poorly in extended heat above 30°C (86°F); blooming diminishes in midsummer heat in many climates
• Often planted as a cool-season annual in spring and autumn
• Can tolerate light frost, surviving temperatures down to approximately -5°C (23°F)

Snapdragons are among the most rewarding cool-season garden flowers, offering vibrant color from spring through early summer and again in autumn in mild climates.

Light:
• Full sun (minimum 6 hours of direct sunlight daily) for best flowering
• Tolerates light partial shade, especially in hot climates where afternoon shade extends bloom life

Soil:
• Well-drained, moderately fertile soil
• Amend heavy clay soils with compost or coarse sand to improve drainage
• Slightly alkaline to neutral pH preferred (6.5–7.5)

Watering:
• Water regularly to keep soil evenly moist but not waterlogged
• Avoid overhead watering to reduce risk of rust fungus (Puccinia antirrhini)
• Reduce watering once established in cooler weather

Temperature:
• Optimal range: 15–24°C (60–75°F)
• Sow seeds indoors 8–10 weeks before the last frost date, or direct sow after last frost
• Seeds require light to germinate; press onto soil surface without covering
• Germination occurs in 7–14 days at 18–21°C (65–70°F)

Planting Tips:
• Pinch back young plants when they reach 10–15 cm tall to encourage bushier growth and more flower spikes
• Deadhead spent blooms to prolong the flowering season
• Tall cultivars (e.g., 'Rocket' series, reaching 75–100 cm) may require staking in windy locations
• Dwarf cultivars (e.g., 'Floral Carpet,' 'Tahiti,' reaching 15–25 cm) are ideal for containers and edging

Propagation:
• Primarily by seed; seeds are very small and should not be buried
• Can also be propagated by stem cuttings taken in late summer
• Some perennial species can be divided in spring

Common Problems:
• Rust (Puccinia antirrhini) — orange-brown pustules on leaves; avoid overhead watering and ensure good air circulation
• Aphids — cluster on new growth; treat with insecticidal soap or neem oil
• Snapdragon rust and downy mildew are the most significant diseases
• Heat-induced dormancy in midsummer; plant in partial shade or choose heat-tolerant cultivars