Fragrant summer lilac - Buddleja davidii 'Empire Blue' (Butterfly Bush)

Buddleja davidii 'Empire Blue' is an ornamental shrub variety in the Scrophulariaceae family, commonly known as the butterfly bush. This plant is prized for its spectacular, fragrant flowers, which attract butterflies, bees, and other pollinating insects, making it an excellent choice for gardens that support biodiversity.

Flower Appearance

• Shape: The flowers are small and tubular, grouped in long, dense panicles (large clusters) that can reach 20-25 cm in length. They grow at the ends of the branches, creating an impressive visual effect, and are prolific nectar producers - a real attraction for bees and butterflies. 
• Color: The flowers are a deep shade of intense blue-violet (sometimes described as true blue), with a small orange “eye” in the center of each flower, creating a subtle yet attractive contrast.
• Fragrance: It gives off a sweet, fruity fragrance, which enhances its appeal to pollinators and adds a pleasant touch to the garden.
• Flowering period: Blooms abundantly from June to October, sometimes until the first frost, especially if faded flowers are regularly removed (deadheading), which encourages continuous flowering.

Growth characteristics

• Height: It grows compactly, reaching a height of 1.5-2 meters and a similar width, making it smaller and easier to fit into gardens than other varieties of Buddleja davidii.
• Foliage: The leaves are lance-shaped, silvery gray-green, with a fine texture and a slightly fuzzy appearance on the underside. They are arranged opposite each other along the branches and provide an elegant backdrop for the vibrant flowers.
• Vigor: A fast-growing shrub, it remains well-proportioned, with arching branches that give it a graceful, airy shape.

Growing conditions

• Exposure: Prefers full sun for abundant flowering, but also tolerates partial shade, although with fewer flowers.
• Soil: Needs well-drained, moderately to highly fertile soil and adapts to various types (clay, sandy), provided water does not stagnate. It tolerates a variable pH (acidic, neutral, or alkaline).
• Watering: Requires moderate watering; it is relatively drought-tolerant once established, but its performance declines in excessively moist conditions.
• Pruning: Severe pruning is recommended in February-March, cutting back to 15-30 cm above the ground to encourage vigorous growth and abundant flowering on new wood. Removing faded flowers throughout the season prolongs flowering. This pruning also delays flowering, reducing the risk of the plant being affected by late frosts. 

Care and hardiness

• Hardiness: It is hardy to temperatures as low as -20°C (USDA zones 5-9), but in colder climates it may die back to the ground in winter, behaving like a herbaceous perennial. In spring, it resumes vigorous growth from the roots.
• Fertilizing: A balanced fertilizer applied in spring supports flowering, but is not strictly necessary in fertile soils.
• Pests and diseases: It can be affected by aphids, spider mites, or mullein moth, but is generally resistant when well ventilated. It may develop mold in damp, poorly drained conditions.

Garden use

Buddleja 'Empire Blue' is ideal for borders, cottage gardens, or as a specimen plant in mixed landscapes. Thanks to its compact size, it is also suitable for containers on patios or balconies. Its blue-violet flowers pair beautifully with yellow plants (e.g. Kniphofia) or white ones (e.g. white roses), creating vibrant contrasts. It is also excellent as a cut flower, thanks to its fragrance and durability.

Origin

Buddleja davidii is native to China and Japan, where it grows naturally on rocky slopes and in disturbed areas. The 'Empire Blue' variety was developed in Great Britain in the 20th century, as part of horticultural selections aimed at enhancing the plant's vivid colors and hardiness. Although precise details about the year or exact breeder are unavailable, 'Empire Blue' is one of the first varieties to popularize true blue shades in Buddleja cultivation, and is valued by gardeners for its color and reliability.