Woody Houseplants: Acacia armata

Kangaroo Thorn, Hedge Wattle Before beginning this section on house plants of a woody nature note should be taken of the fact that it could also include certain plants of this kind with decorative flowers (such as hibiscus, fuchsia) or with decorative foliage (such as ficus). Likewise, certain species included here might just as easily be described in other sections (for example bougainvillea in the section on climbers). Such inaccuracies always occur whenever a book is arbitrarily divided in such a manner and there is nothing the author can do but beg the reader’s tolerance.

Acacias are known to practically everyone for come spring they are on display in every florist’s window. They are either shrubs or small trees with flowers, coloured yellow as a rule, arranged in ball-like clusters or cylindrical spikes. The foliage is composed of bipinnate leaves or phyllodes, that is leaf stalks of an expanded and flattened form resembling and having the functions of leaves. In most species the leaflets are changed into spines.

Acacia armata (syn. A. paradoxd) is a native of Australia where it grows as a tree up to 5 m (16 ft) high. In cultivation, however, it is a much smaller, thickly-branched shrub. The foliage is made up of phyllodes about 2 cm (¾ in) long with a single vein. The leaflets have been modified into paired persistent spines. In March or April the plant bears a great profusion of yellow flower clusters.

Of the species with pinnate leaves most often encountered in cultivation are: A. drummondii, with short flower-spikes about 3 to 4 cm (l-¼ to 1-½ in) long, and A. pulchella with ball-like flower clusters. Both are indigenous to Australia.

Of particular interest are acacias that live in a sym-biotic relationship with ants, for example A. sphae-rocephala from Mexico. Its hollow, inflated, reddish-brown spines are inhabited by ants that feed on small yellowish, protein-rich particles formed at the tips of the leaflets.

Acacias may be grown indoors only if they can be provided with cool conditions in winter (about 5 to 10°C [41 to 50°F]). The biologically interesting ant acacias can withstand higher temperatures. The growing medium should be a nourishing, peaty com-post, such as one of the proprietary soilless composts. In summer the plants should be watered and fed liberally. Propagation is by cuttings or by seed.

15. November 2011 by Dave Pinkney
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