Buddleja
Buddleja davidii (white flowered form)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Lamiales
Family:	Scrophulariaceae
Tribe:	Buddlejeae
Genus:	Buddleja L.
Type species
Buddleja americana L.[1]
Species
About 140 species, see text.
Synonyms
Adenoplea Radlk. Adenoplusia Radlk. Buddleia L., orth. var. Chilianthus Burch.[2]

Buddleja (/ˈbʌdliə/; orth. var. Buddleia; also historically given as Buddlea) is a genus comprising over 140^[3] species of flowering plants endemic to Asia, Africa, and the Americas. The generic name bestowed by Linnaeus posthumously honoured the Reverend Adam Buddle (1662–1715), an English botanist and rector, at the suggestion of William Houstoun.^[4] 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. Buddleja species, especially Buddleja davidii and interspecific hybrids, are commonly known as butterfly bushes and are frequently cultivated as garden shrubs.^[5] Buddleja davidii has become an invasive species in both Europe and North America.^[6]

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 his Species Plantarum of 1753 and 1754 spelled it Buddleja, with the long i between two vowels, common in early modern orthography.^[7] The pronunciation of the long i in Buddleja as j is a common modern error. 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.^[8]

The genus Buddleja is now included in Scrophulariaceae, having earlier been classified under Buddlejaceae (synonym: Oftiaceae) and Loganiaceae^[9]

Of the approximately 140 species, nearly all are shrubs less than 5 m (16 ft) tall, but a few qualify as trees, the largest reaching 30 m (98 ft). Both evergreen and deciduous species occur, in tropical and temperate regions respectively. 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 (0.4–11.8 in) long.^[10] The flowers of the Asiatic species are mostly produced in terminal panicles 10–50 cm (4–20 in) long; the American species more commonly as cymes forming small, globose heads. Each individual flower is tubular and divided into four spreading lobes (petals) about 3–4 mm (0.12–0.16 in) across, the corolla length ranging from around 10 mm in the Asiatics to 3–30 mm in the American species, the wider variation in the latter because some South American species have evolved long red flowers to attract hummingbirds, rather than insects, as exclusive pollinators.^[11]

The colour of the flowers varies widely, from mostly pastel pinks and blues in Asia, to vibrant yellows and reds in the New World, while many cultivars have deeper tones. The flowers are generally rich in nectar and often strongly honey-scented. The fruit is a small capsule about 1 cm (0.39 in) long and 1–2 mm (0.04–0.08 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.^[12]

The genus is found in four continents. Over 60 species are native through the New World from the southern United States to southern 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.

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.^[13] Several species are popular garden plants and 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.

The most popular cultivated species is Buddleja davidii from central China, named for the French Basque missionary and 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 a cross between a South American and an Asiatic species.^[14]

Some species commonly escape from the garden. B. davidii in particular is an extensive coloniser of dry open ground. In urban areas in the United Kingdom, it often self-sows on waste ground or old masonry, where it grows into a dense thicket. A number of agricultural organizations and governing authorities throughout the world have designated the plant as an invasive species or a noxious weed.^[15] It is frequently seen in the United Kingdom beside railway lines, on the sites of derelict factories and other buildings and, in the aftermath of World War II, on urban bomb sites.^[16][17] That earned it the popular nickname of "the bomb site plant".^[17]

Popular garden cultivars include 'Royal Red' (reddish-purple flowers), 'Black Knight' (very dark purple), 'Sungold' (golden yellow), and 'Pink Delight' (pure pink). In recent years, much breeding work has been undertaken to create seed sterile cultivars (see "Non-invasive" Buddleja cultivars). This is a particularly important consideration in the United States, where several states have banned B. davidii and its fertile cultivars because of their invasiveness.^[18] Unlike native B. davidii, some of these "non-invasive" cultivars are small and compact, such as 'Blue Chip', which only reaches a height of 46 cm (1.51 ft) and a width of 1.4 m (4.6 ft).^[19]

The many species of Buddleja have been the subject of much taxonomic contention. The listing below includes the names, still prevalent in horticulture, of many former Asiatic species sunk by the late Toon Leeuwenberg as Buddleja crispa and adopted as such in the definitive Flora of China.^[20][21][22]

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

• 
  B. davidii – Invasive species, here in an urban area
• 
  Buddleja madagascariensis – flowers and foliage
• 
  Unidentified Buddleja species in Igarata, Brazil
• 
  Monarch butterfly feeding on Buddleja davidii in Connecticut
• 
  Red Admiral butterfly feeding on Buddleja officinalis in January

The following Buddleja species and cultivars are (2017) holders of the Royal Horticultural Society's Award of Garden Merit:

• Leeuwenberg, A. J. M. (1979) The Loganiaceae of Africa XVIII Buddleja L. II, Revision of the African & Asiatic species. H. Veenman & Zonen, Wageningen, Nederland.

• Norman, E. (2000). Buddlejaceae. Flora Neotropica, Vol. 81. New York Botanical Garden, USA. ISSN 0071-5794

• Stuart, D. (2006). Buddlejas. RHS Plant Collector Guide. Timber Press, Oregon, USA. ISBN 978-0-88192-688-0

Wikimedia Commons has media related to Buddleja.

Wikispecies has information related to Buddleja.

• Buddleja globosa pictures from Chilebosque.
• Reference to nomenclature issue