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Sunday, September 8, 2013

Bitter Bush (Selago canescens)

Family Scrophulariaceae
Selago canescens bursts into flower in early spring when most plants in the garden are still recovering after the cold winter. An added attraction is the butterflies that visit the clusters of mauve flowers on windless, warm days.

Selago canescens is an evergreen shrub with many long slender branches and grows between 1 and 1.5 m high. The glossy green leaves are short, narrow and soft. They arise in dense tufts along the main branches and side shoots, making the plant attractive throughout the year. Each individual flower is tiny and consists of a thin tube opening into 5 petals. The masses of small flowers in tight clusters along the stem form long mauve spikes that are very attractive and showy when in flower (July-September). The tiny grey seeds ripen about a month after flowering.

Conservation status

Selago canescens is endemic to the unique fynbos flora, which means it occurs only in the Cape and nowhere else in the world. Luckily it is still common in its natural habitat and not regarded as threatened.

Distribution and habitat

Selago canescens grows naturally on the dry, mostly clay slopes from Cape Town along the east coast to Port Elizabeth. The climate at the Cape is typically Mediterranean with winter rain and dry, hot summers, whereas the eastern parts receive substantial summer rains. Frost is not common along its distribution, but the shrubs do have the ability to resprout after pruning and should be able to survive light frost.

Derivation of name and historical aspects

The genus Selago was first described by the Swedish-born naturalist Carolus Linnaeus in 1753. The name is a combination of the words, sel, meaning sight, and jach, meaning salutary that refers to the supposed medicinal properties. The species name canescens is the Latin for 'covered with dense, fine, greyish white hairs'.

Butterflies are attracted by the masses of small, tubular purple flowers containing nectar. Many Selago species act as host plants to butterflies of the Lepidochrysops genus commonly known as Ant Blues. These butterflies have an interesting and important association with ants as a survival strategy for their larvae. The female butterflies lay their single egg on the flower bud or ovary of the Selago species where the host ant is active. The young larva bores into the plant ovary, eating the ovules and later emerges from its shelter to attract an ant which carries it into its nest where the larva preys on the ant brood.

The appearance of butterflies is influenced by the availability of plant foods for their larvae. In the Western Cape with cold, wet winters (May to August) and hot, dry, windy summers (late November to March), plant growth is most vigorous in the spring (September to March). Butterflies follow this natural pattern with most species active in spring and early summer.

Uses and cultural aspects

Selago canescens is a popular shrub at Kirstenbosch especially in the herbaceous plantings. With its striking early spring colour it is very effective in large, sweeping plantings. In the butterfly bed it is planted with many other mauve flowers such as Scabiosa africana, Vernonia glabra, Polygala fruticosa, Buddleja salviifolia, Pelargonium cucullatum and Geranium multisectum.