﻿AN ECONOMIC STUDY OF ACACIAS. 3 



CHARACTERISTICS OF VARIOUS SPECIES. 



SOIL AND MOISTURE REQUIREMENTS. 



Acacias form one of the most conspicuous associations of all those 

 which group themselves close to deserts. While they do not con- 

 stitute a true desert species, they nevertheless carry tree life well 

 into t*he desert regions, becoming shrubby and scattered. In fact, 

 some species, such as Acacia greggi, one of the most valuable lac-insect 

 bearing species, will thrive with only 3 inches of rainfall; some 

 grow on inland sand dunes far from ocean influences. With a few 

 notable exceptions, the acacias are preeminently adapted to "poor 

 soil and rainless summers and to semiarid conditions, though most 

 of them respond to good soil and abundant moisture. Their great 

 drought-resisting qualities come from their deep, strong root systems 

 and from their leaves, which are chiefly phyllodes, or flattened 

 stems, with sensitive specialized powers of movement by which 

 evaporation may be greatly lessened. 



A light, warm, well-drained soil, if cultivated, will produce rapid 

 growth, and the rich and heavy soils which some of the eucalypts 

 demand for their best development are not necessary for the acacias. 

 The most prominent exception to this is Acacia melanoxylon, or " black 

 wood," which produces choice timber but has little value for tanning 

 unless the tannic acid is concentrated by the extract method. This 

 is a river-bottom species, associated with Eucalyptus globulus and 

 other trees of that type. 



Acacias readily adapt themselves to a heavier precipitation and 

 more tropic conditions than characterize their native soil, as proved 

 by many years of growth in the Hawaiian Islands and on the Natal 

 coast of Africa. Indeed, many species, as with the eucalypts, when 

 introduced elsewhere, may grow even more rapidly than in their 

 native region. But mainly the significant fact about the tree, so 

 far as moisture conditions are concerned, is that it does not require 

 a heavy annual rainfall nor any summer rain. It is this character- 

 istic which renders it valuable on the southern Pacific coast and in 

 the Southwest. It must be kept in mind that the trees are only 

 half hardy as regards frost, and will not endure a temperature below 

 16° F. or 20° where the cold is likely to be sustained. 



So far as known, no other semitropic trees of high economic value 

 possess to so great an extent the ability to thrive upon and to 

 improve a great variety of arid and sterile soils. Through their 

 agency laffge areas of land unfit for ordinary cultivation, and at 

 present producing only a scanty pasturage at best, may be reclaimed 

 and utilized. Recent discoveries in the nitrogen-fixing qualities of 

 the legumes point to the possibility of a hitherto unrecognized value 

 in acacia growing. 



