Tuesday, April 15, 2008

Family: Asteraceae (Compositae)


Class: Dicotyledoneae (Angiospermae) Order: Asterales Common names: daisy family, sunflower family, thistle family (Eng.); madeliefie-familie, sonneblom-familie (Afr.) This is probably the largest family of flowering plants, with more than 25 000 species world-wide, growing from sea-level to the highest mountain peaks. It is absent only from Antarctica. In southern Africa it is also one of the biggest families of flowering plants with about 246 genera and 2 300 species. Many of the species have economic value. They show remarkable variation in growth form and general morphology because they occur in so many different localities and habitats. Derivation of name and subdivisions: The alternative family name Compositae is derived from the Latin word compositus which means 'made up of parts united in one common whole'. This refers to the collection of different florets arranged together in an inflorescence. For family names, the modern tendency in taxonomy is to use the name of a familiar plant in a certain family and to add the suffix -aceae to the name. In this way the family name Asteraceae is made up by using the name Aster and adding -aceae. The family is divided into three subfamilies and a number of tribes. In the National Herbarium, Pretoria, we accept 18 tribes. Description Almost all the features generally occurring in plants, can be found in this family! There are annual, biennial or perennial herbs, dwarf shrubs, shrubs, a few trees, some scramblers and aquatics. Some are succulent, whereas while others are spiny and some have milky sap. Many perennial species are adapted to survive the cold, dry winter season of the highveld by underground storage organs and producing annual stems in spring. The leaves can be arranged alternately, opposite or whorled along the stem; sometimes they are situated at the base of the stem (radical and rosulate) or in groups. Some have a petiole while others are sessile. The leaves can be simple with smooth margins or the margins can be toothed, lobed or variously dissected to such an extent that the leaves are actually compound with numerous leaf segments. Many species in the karroo and fynbos vegetation have small, needle-like leaves to survive the hot, dry summer seasons. These leaves look almost like the leaves of the genus Erica, and are called ericoid. The 'flowers' are the feature that distinguishes this family from all other plant families. Uses and economic value The economic value of the representatives of this family can be divided into various categories: food for man and beast, poisonous, weeds, medicinal, wood, garden plants and cut flowers. Food for man: The most well known food product of the family is certainly sunflower oil and kernels. Other well-known foods are Jerusalem and French artichokes, lettuce, chicory and herbal tea like camomile. Food for animals:species of this family grow in so many habitats and localities, many of them are good grazing for stock e.g. sandbietou or tickberry (Chrysanthemoides monilifera subsp. pisifera), blouheuningkaroo (Felicia muricata), witheuningkaroo (Phymaspermum parvifolium) and bierbos (Pteronia membranacea). Poisonous species: There are, however, many species that are poisonous to stock e.g. vermeerbos (Geigeria species), kaalsiektebos (Chrysocoma ciliata) and bloubietou (Dimorphotheca spectabilis). Weeds: The fruits (cypselas) with their hair or scale-like pappus are easily distributed by the wind. Therefore many species have become weeds and some are distributed world-wide. Well-known weeds are dandelions (Taraxacum species), cosmos (Cosmos bipinnatus), blackjack (Bidens species) and burweed or boetebossie (Xanthium spinosum). Medicinal: Many species have traditionally been used medicinally as they are so easily obtainable. Many of the medicinal plants belong to the tribe Anthemideae, whose representatives are often aromatic. Well-known medicinal plants are wilde-als or African wormwood (Artemisia afra), kapokbos or wild rosemary (Eriocephalus africanus) and wild camphor bush (Tarchonanthus camphoratus). Wood: In southern Africa, representatives of only six genera are classified as trees, but the wood of only two genera, wild silver oaks (Brachylaena species) and wild camphor trees (Tarchonanthus species), have been reported as being used for building huts, fence posts, handles of utensils and turnery. Garden plants and cut flowers: Did you know that the edelweiss (Leontopodium alpinum) that acquired fame in the musical The sound of music, belongs to the family Asteraceae? The most well-known daisy South Africa gave the world, is the Barberton daisy (Gerbera spp.) Today there are many varieties and cultivars available on the market. Familiar cutflowers are asters, dahlias, chrysanthemums, cornflowers and sunflowers, The full potential of South African daisies for gardening has not been exploited yet. There are many different South African species that can be cultivated successfully. Those that have featured in this series include: Arctotis arctotoides Athanasia dentata Cineraria saxifraga Dimorphotheca pluvialis Dimorphotheca sinuata Euryops virgineus Felicia echinata Felicia heterophylla Gerbera aurantiaca Gebera jamesonii Helichrysum umbraculigerum Helichrysum splendidum Kleinia fulgens Oldenburgia grandis Senecio macroglossus Senecio elegans Ursinia cakilefolia Vernonia hirsuta Please use the site search facility to find others ( Enter Asteraceae as the search term). It is important to plant daisies in full sun or where they will receive sun for at least half the day to ensure that the 'flowers' will open to their full glory. They are normally easy to grow and do not need much attention. Author; P.P.J. Herman, National Herbarium, Pretoria

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