Hybridises with: Orange-Ball-Tree producing Weyer's Butterfly-Bush (buddleja × weyeriana), a Butterfly-Bush type plant with orange-coloured flowers that are not as compactly spherical as are those of the Orange-Ball-Tree.
Slight resemblance to : Purple Loosestrife but only insofar as that too has a purple spike of flowers, often arching on larger plants.
Distinguishing Feature : Its long arching branches with a dense terminal spike of purple or mauve flowers consisting of hundreds of trumpet-shaped petals ending splayed into four short petals. The inner tube of the flowers is a striking and harshly contrasting yellow-orange colour.
Butterfly Bush obtains its name because it attracts butterflies which often land on its flowers. A tall bush or shrub to 8 metres tall, but often much shorter, popularly grown in gardens. There are a great many varieties of Buddleja grown for gardens, some mainly white, others orange, a few red, but these too can escape into the wild fairly easily, especially the white variety.
Butterfly Bush also has a reputation for growing wild and behaving very weedishly, especially in walls and canal abutments. It spreads rapidly in an urban environment quickly establishing itself in the brickwork of buildings and even in tall mill chimneys, where it can damage the brickwork causing great damage. It runs rampant over industrial land, derelict land and land due for development and along railways and can rapidly colonize whole areas. It is worst on disturbed land. It is a problem that seems to be un-addressed in the UK.
VOLATILE FRAGRANT COMPOUNDS
Oxoisophorones are volatile fragrant terpenoids which smell sweetish and surround the flowers. These compounds elicit an antennae response in many butterflies, which is what probably attracts them (and nocturnal moths) to the bush. Note that the oxide is just the epoxide of the former, breaking the double bond with a bridging oxygen atom. They are based upon
(E)(E)-α-Farnesene is a sesquiterpene and the same Farnesene that is featured elsewhere in this tome and is the one most commonly encountered in the plant world. It is found in the sticky coating on Apple and other fruits smelling of 'green apples'. In air it oxidises, the oxidation products being damaging to the fruit, resulting in a storage disorder known as 'scald'. It also acts as a semiochemical, sending a chemical alarm pheromone to insects such as termites whilst at the same time acting as a food attractant to Codling Moths who will eat the Apples.