This group consists of about 1,000 species that are found in tropical and subtropical regions, especially in Australia and Africa. These evergreens should not be confused with the trees and shrubs commonly known as acacia, which belong to the group Robinia. These tender evergreens are totally different and are commonly known as Mimosas and Wattles. The Australian types are called Wattles because their lumber was used by early settlers in the wattle-and-daub method of building homes. The attractive leaves of these plants are usually bipinnate, giving them a feathery appearance. Some, however, are phyllodes; these are expanded, flattened leaf stems that carry out the same functions of true leaves. Wattles mostly bear flowers in the winter or spring. The tiny yellow flowers are produced in small, fluffy, round- or bottlebrush-shaped clusters. A. armata (Kangaroo Thorn) is a large, thorny, dense shrub with small, slender, dark green phyllodes. In the spring, the length of the branches are clothed with tons of yellow flowers. A. baileyana var.
Purpurea is a large shrub or small tree with pretty, feathery leaves that are deep purple when young, contrasting beautifully with the older, blue-green leaves. A. pravissima (Ovens Wattle) forms a small tree or large shrub with blue-green, triangular phyllodes. Each phyllode is equipped with a single thorn on its under side. Tons of small clusters of yellow flowers are borne early in the spring. Some of these plants are valued for their timber such as A. homalophylla (Myall Wood), A. melanoxylon (Australian Blackwood), A. decurrens dealbata (Silver Wattle), and A. acuminata (Raspberry Jam Wood). The hard, durable wood from some is used in different countries for building purposes, making furniture, tool handles and much more. Some Acacias are valued for the tannin in their bark or wood. Gum Arabic is a gum that exudes from the stems and branches of A. nilotica; this plant is found wild in the dry areas of tropical Africa and India. This gum is used for dyeing and printing. A perfume is obtained from the flowers of A. Farnesiana. This plant is grown commercially in southern France.
Wattles can only be grown outdoors in tropical climates. They should be grown in neutral or acidic soil that is on the dry side. They will not survive in shallow, alkaline soil. When Acacias are grown in pots in a greenhouse, the temperature should be 45-50º F. from October to May. However, throughout the rest of year they can be set outdoors in a sunny area with the pots buried to the rims in ashes; this treatment ripens the shoots that will bloom the following spring. As soon as the flowers have faded, the plants should be repotted in equal parts of peat and loam with a liberal amount of sand mixed in. The soil needs to be patted firm. After potting, sprits the plants often and keep the greenhouse humid until new growth begins, at which time the greenhouse should be ventilated more and more until June, when they may be set outside again.
Seeds can be sown in the spring and summer. The seeds have hard skins and must be chipped with a penknife carefully so as not to damage the "eye". They should then be soaked in warm water for 24 hours before planting. They should be set half an inch deep in well-drained pots filled with equal parts of sandy loam and peat. Place the pots in a propagating case in the greenhouse and cover with glass to keep the soil moist. When the seedlings show, place the pots on the open greenhouse bench for a few weeks and then plant separately in 3-inch pots filled with sandy loam and peat moss with an addition of sand. Cuttings can also be taken in June or July when the shoots are semi-woody. Short side shoots are detached with a piece of branch attached and inserted in pots of the soil mixture described above. Cover them with a bell jar and be sure to wipe the moisture off the inside of the jar every morning. When the cuttings are rooted they are gradually hardened off, as for seedlings. When the plants are 4 inches long they need to be shortened to 3 inches.
The side shoots must also be cut back similarly to produce plants with several branches. When Acacias are grown for climbing purposes over pillars or greenhouse roofs, they should be planted in a bed of sandy, peaty loam and the shoots should be tied to their supports. Every year the weaker shoots should be pruned out and after the flowers have faded the side branches should be shortened. When they're grown in small pots they should be pruned by shortening their shoots to about half their length after flowering.