Dictamnus

Dictamnus is a monotypic genus of flowering plants in the family Rutaceae. The species, Dictamnus albus, is also known as burning bush, dittany, gas plant or fraxinella. This herbaceous perennial has several geographical variants. It is native to warm, open woodland habitats in southern Europe, north Africa and much of Asia.

Description
This plant grows about 40 cm (16 in) to 100 cm (39 in) high. Its flowers form a loose pyramidal spike and vary in colour from pale purple to white. The flowers are five-petalled with long projecting stamens. The leaves resemble those of an ash tree.

Volatile oils
The name "burning bush" derives from the volatile oils produced by the plant, which can catch fire readily in hot weather, leading to comparisons with the burning bush of the Bible, including the suggestion that this is the plant involved there. The daughter of Swedish botanist Carl Linnaeus is said to have ignited the air once, at the end of a particularly hot, windless summer day, above Dictamnus plants, using a simple matchstick. The volatile oils have a reputed component of isoprene.

Cultivation
Several varieties and cultivars have been selected for garden use. The variety D. albus var. purpureus in which the violet-purple is confined to veining of white petals with a slight blush, has gained the Royal Horticultural Society's Award of Garden Merit. Dictamnus is tap-rooted, making mature plants difficult to establish and resistant to division; young plants often need three years before they begin to flower, and since it is late to break into leaf in spring, even quite mature clumps may be harmed with vigorous soil-working in spring. For all these reasons, added to toxicity of the foliage, Dictamnus is rarely seen in American gardens.
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