Pod Bearing Trees - Acacias, Or Wattles
( Originally Published 1927 )
Australia has contributed to southern California's tree flora a large number of forms of the acacia tribe, shrubs and trees of great variety and beauty of flowers and ever-green foliage. They are hardy and perfectly at home, and are planted in such profusion as to be the commonest of all street and ornamental trees. The leaves are set on a branching pinnate stem, making them "twice compound" of many tiny leaflets, fascicled on the sides of the twigs, alternate on the terminal shoots of the season. The lacy, fern-like foliage of most acacias would justify the planting of them for this trait alone. But the abundant mass of bloom usually overwhelms the tree-tops, obscuring the foliage with a veil of golden mesh. Sometimes white, but oftenest yellow, the individual flowers are very small; but they crowd in button-like heads or elongated spikes, set close in axillary clusters. In their native woods these trees flower much less freely than in the land of their adoption. The curling pods are in most species and varieties ornamental, as they pass through many color changes before they finally discharge their seeds.
Acacias compose a genus of four hundred species, and an untold and constantly increasing number of cultivated varieties. The continent of Australia has the greatest re-presentation of native species. Others belong to Africa—. tropical, northern, and southern regions. Asia, in its warmer southern territory, and in southwestern China, has many native acacias. Tropical and temperate South America, the West Indies, Central America, Mexico, the southwestern region of the United States, and the islands of the South Pacific, all have representatives of this wonderful and far-scattered genus. There is no country interested in horticulture that does not grow acacias as ornamental shrubs and trees, even if they must be grown under glass the year round. In southern England the acacias, grown in open ground, and known as "tassel trees," attain good size.
Valuable lumber, tanbarks, dyes, perfumes, and drugs are yielded by acacias. Gum Arabic is the dried sap of several oriental species, particularly, Acacia Arabica, Linn. of Egypt and southern Asia.
As a rule, acacias have slender branches armed with spines. Often these are too small to attract notice, or to make the species useful as a hedge plant. All spines are modifications of the stipules at the base of leaf or leaflet. Thorns, however, are modified twigs, strong, stiff and sharp, often branched. The honey locust shows true thorns, not spines or prickles. The armament of canes of blackberry is only skin deep. This means of defence is best, called "prickles."
The Black Acacia
The black acacia, called at home in Australian woods, the "blackwood-tree," for its black heart-wood, is a familiar street and shade tree in California. In narrow parkings it is likely to surprise the planter by outgrowing in a few years the space allotted to it, and upheaving both cement walk and curb, by the irresistible force of its thick roots. It is one of the large timber acacias, and even in the cool climate of England reaches fifty feet.
In suitable situations in California it grows much higher, and its compact conical head of dense evergreen foliage, gives abundant shade at all seasons. The flowers are white or cream-colored, lightening the yellow-green of the new shoots and the dull, opaque of the older leaves, with abundant clusters in earliest spring. The succeeding fruits are curling thin pods that hang in brownish sheaves, giving the tree a rusty look. Each seed is rimmed with a frill of terra cotta hue that serves as a wing for its flight, when detached by the wind. The roots send up suckers and the seeds are quick to grow. So any one can have black acacias with little trouble or expense. Its shedding of leaves and pods makes much litter, however, a trait sometimes overlooked which seriously diminishes its desirability as a street and shade tree.
The Silver Wattle
The silver wattle of nursery catalogues is named for its abundant, silvery-pubescent, feathery foliage. Its flowers—fluffy golden balls, small but abundant—make this a wonderfully showy tree.
Sea-green and turquoise-blue leaves, with abundant canary-yellow bloom, are traits of many different acacias in cultivation, all of which are rapid growers, and soon re-pay the planter who wants quick results. From being mere ornaments they rise to the stature of shade trees, and merely multiply the charms that made them admired when young. Varieties with sharp spines are employed as hedge plants. Curious leaf forms and unusual, edgewise position of the foliage, make us wonder at some of the glorious "golden wattles" and "knife-leaved acacias," that bring us glimpses of the forests of Australia and other strange far countries.