Wednesday, April 10, 2013

Important Plant Families in South Africa - Rutaceae

In order to facilitate the identification of our wealth of lovely South African trees, it is helpful to be familiar with the most prominent plant families in an area as well as the characteristics that distinguish each plant family. Every month we will feature one of the most important and well represented plant families, focusing on easily recognisable features to assist identification.

Rutaceae (Citrus family)

This large and widespread family is well known world wide and is represented by about 26 tree species in South Africa. Most of the plants in this family have aromatic glands in the leaves that release a distinctive, often citrus like fragrance when crushed. These glands can be seen as translucent dots by holding the leaves up to the light.

Members of this family are generally easy to identify as trees that have alternate, trifoliate, palmate or pinnate leaves with secretory cavities in the lamina usually belong to this group. The exception is Calodendrum capense (Cape chestnut) in that it has opposite as well as simple leaves.

The flowers of the Rutaceae family can be easily identified by the large or superior ovary and the presence of 10 or fewer stamens.

The Rutaceae family is of great economic importance with the most valuable members yielding citrus fruits such as oranges, lemons, mandarins, limes, tangerines and grapefruit. Numerous species are cultivated for their precious essential oils such as Neroli and Bergamot that are used in the natural healing and perfume industries. All the various types of buchu that are highly regarded for their diverse medicinal properties are obtained from shrubs belonging to this family. Ruta graveolens (Rue) is another popular medicinal plant belonging to this group. Some of the forest species yield an attractive, yellowish timber that is used for furniture.

Members of this family include the beautiful Calodendrum capense (Cape chestnut), Zanthoxylum davyi (Knobwood), Vepris undulata (White ironwood), Clausena anisata (Horsewood), Fagaropsis angolensis (Fagaropsis) and Zanthoxylum capense (Small knobwood).

Classification Euphorbia family

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