Buddleja, or Buddleia ( /ˈbʌdliːə/) but commonly known as the Butterfly Bush,^[4] is a genus of flowering plants. The generic name bestowed by Linnaeus posthumously honoured the Reverend Adam Buddle (1662–1715), a botanist and rector in Essex, England, at the suggestion of Dr William Houstoun. Houstoun sent the first plants to become known to science as buddleja (B. americana) to England from the Caribbean about 15 years after Buddle's death.[1]

Classification

The genus Buddleja is now included in the figwort family, Scrophulariaceae;^[5] it had earlier been classified in either the Loganiaceae or in a family of its own, the Buddlejaceae.

Description

Of the approximately 100 species nearly all are shrubs <5 m (16 ft) tall, but a few qualify as trees, the largest reaching 30 m (98 ft). Both evergreen and deciduous species occur. The leaves are lanceolate in most species, and arranged in opposite pairs on the stems (alternate in one species, B. alternifolia); they range from 1–30 cm (0.39–12 in) long. The flowers are produced in dense panicles 10–50 cm (3.9–20 in) long; each individual flower is tubular, about 1 cm (0.39 in) long, with the corolla divided into four spreading lobes (petals), about 3–4 mm (0.12–0.16 in) across. Flower colour varies widely, with white, pink, red, purple, orange or yellow flowers produced by different species and cultivars; they are rich in nectar and often strongly scented. The fruit is a small capsule about 1 cm (0.39 in) long and 1–2 mm (0.039–0.079 in) diameter, containing numerous small seeds; in a few species (previously classified in the separate genus Nicodemia) the capsule is soft and fleshy, forming a berry.

Distribution

The genus is endemic to four continents. Over 60 species are native throughout the warmer parts of the New World from the southern United States south to Chile, while many other species are found in the Old World, in Africa, and parts of Asia, but all are absent as natives from Europe and Australasia. The species are divided into three groups based on their floral type: those in the New World are mostly dioecious (occasionally hermaphrodite or trioecious), while those in the Old World are exclusively hermaphrodite with perfect flowers.

Cultivation and uses

As garden shrubs Buddlejas are essentially 20th-century plants, with the exception of B. globosa which was introduced to Britain from southern Chile in 1774 and disseminated from the nursery of Lee and Kennedy, Hammersmith.^[6] Several species are popular garden plants, the species are commonly known as 'butterfly bushes' owing to their attractiveness to butterflies, and have become staples of the modern butterfly garden; they are also attractive to bees and moths. Some species of South American Buddleja have evolved long red flowers to attract hummingbirds as exclusive pollinators.

The most popular cultivated species is Buddleja davidii from central China, named after the French naturalist Père Armand David. Other common garden species include the aforementioned B. globosa, grown for its strongly honey - scented orange globular inflorescences, and the weeping Buddleja alternifolia. Several interspecific hybrids have been made, notably B. 'Lochinch' (B. davidii × B. fallowiana) and B. × weyeriana (B. globosa × B. davidii), the latter the only known cross between a South American and an Asiatic species.

Some species commonly escape from the garden. B. davidii in particular is a great coloniser of dry open ground; in towns in the United Kingdom, it often self-sows on waste ground or old masonry, where it grows into a dense thicket, and it is listed as an invasive species in many areas. It is frequently seen beside railway lines, on derelict factory sites and, in the aftermath of the Second World War, on urban bomb sites. This earned it the popular nickname of 'the bombsite plant' among people of the war-time generation.

Popular garden cultivars include 'Royal Red' (reddish-purple flowers), 'Black Knight' (very dark purple), 'Sungold' (golden yellow), and 'Pink Delight' (pink). In recent years, much breeding work has been undertaken to create more compact buddlejas, most recently the production of dwarf varieties such as 'Blue Chip' (Lo & Behold™) and 'Buzz' which reach no more than 2–3 ft (0.61–0.91 m) tall, and are also seed sterile, an important consideration in the USA where B. davidii and its cultivars are banned from many states on account of their invasiveness.

Nomenclature

The botanic name has been the source of some confusion. By modern practice of botanical Latin, the spelling of a generic name made from 'Buddle' would be Buddleia, but Linnaeus in 1753 and 1754 spelled it Buddleja. The International Code of Botanical Nomenclature has gradually changed to incorporate stricter rules about orthographic variants, and as of the 2006 edition requires (article 60, particularly 60.5) that Linnaeus' spelling should be followed in this case.

Species

The many species of Buddleja have been the subject of much taxonomic contention. The listing below is based on the most recent reviews of the genus, by the late Anthonius Leeuwenberg (Asiatic and African species) in 1979, and Eliane Norman (American species) in 2000 (see Monographs). In the former's work, a number of 'species' were controversially sunk as varieties.^[7][8][9]

Formerly placed here

• Cephalanthus glabratus (Spreng.) K.Schum. (as B. glabrata Spreng.)

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