This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
A cheat number of species belonging to this genus are known to botanists. Several are natives of tropical regions; but those found growing in the more temperate parts of Australia are, from a horticultural point of view, the most valuable, and it is of them that we would speak in this paper. Those Australian species with which the writer is acquainted are all extremely handsome plants, both as regards their habit or style of growth, and the graceful foliage they bear. The foliage of some species, as, for instance, that of A. dealbata, vies in graceful beauty with the fronds of most kinds of Adiantums or Maidenhair Fern. Young plants of A. dealbata, of from 1 to 3 feet high, are very useful and appropriate for room decoration. Another species, with fern-like foliage, and equally suitable for the same purpose, is A. lophantha. This latter species is a stronger grower, and coarser in all its parts than the former. The two, however, have a striking resemblance (especially their flowers) to each other.
A. pubescens, like the two former species, is furnished with bipin-nate leaves, and is as desirable a plant to cultivate. All the Australian species have yellow-coloured flowers - some being of an intense golden colour, while others are of a pale lemon or canary colour. Their shape differs somewhat on different species : for instance, the flowers of A. armata appear like little golden balls springing from the axils of the leaves, while those of most other species resemble miniu-ture lemon-coloured bottle-brushes.
The various species of Acacia to which we are at present referring are free-growing, easily managed plants; and seeing that this is the case, and that they produce their flowers freely during the winter and spring months in this country, it is somewhat strange that so few of them are to be met with in general cultivation, especially when we remember that in addition to their free-flowering habit they are clothed, at least several of them, with very ornamental foliage that renders them at all seasons, whether in bloom or otherwise, attractive objects in whatever position they are placed.
A large healthy bush of A. armata when in full bloom during the winter months is a very telling plant for conservatory decoration, especially if arranged in combination with stately Palms such as Kentia Australis or Seafortha elegans. Then A. Drummondii when in flower is a real gem, and fit to occupy a place in any position where flowering plants are admissible. This species is of a more slender and twiggy growth than any of the others that we have mentioned; and if the cultivator keeps it in good health, and free from red-spider and other insect pests or enemies, it will not fail to reward him with an ample crop of flowers for his trouble and attention.
Another species, A. Riccanna, deserves to be specially mentioned. Its style of growth is distinct from that of any of the species mentioned. The branches, foliage, and flowers of this plant assume a drooping position, that imparts to it a very pleasing and interesting appearance at all seasons of the year. It succeeds admirably under pot-culture, although I have heard the reverse stated; and when planted out in a prepared border, it is excellent for training on the rafters of large conservatories or other cool glass structures of large dimensions.
There are several other species that deserve to be mentioned, but those already named are sufficient to direct attention to the at present partially neglected genus Acacia, and I will now add a few notes of a cultural kind.
Acacias may be increased by cuttings, layers, or by grafting. By seeds, however, is the quickest and best method of propagating them. Seeds of most kinds can be obtained at a cheap rate from any respectable house in the seed trade. If good, they germinate quickly at any season of the year if placed in a bottom-heat of from 60° to 70°. The best time, however, to sow them is in the months of March and April. Before the seeds are sown it is advisable to soak them for twelve or fourteen hours in water; and if the water, at the time they are put into it, is at a temperature of 100°, no harm but good will follow.
The seeds should be covered about half an inch with the compost, which should consist of sandy loam, and be pressed firmly on to them.
As soon as they are sown, give a good watering through a fine-rosed watering-pot, and place the pots or pans containing them in a bottom-heat as above indicated, and cover them with a bell-glass. In a short time the young plants will appear, and as soon as they are fit to handle, pot them separately into small pots, draining the latter in a proper way, and using a compost similar to that in which the seeds were sown. When the young plants have got their first shift from the seed-pan, give them a good watering, and place them near to the glass in a frame or pit, keeping the latter moist and the plants shaded until their roots have taken hold of the fresh soil, which will be in a few days. The shading should then be removed, and except in the case of very bright sunshine, it need not be again applied. A constant supply of fresh air should play about the plants during the summer and autumn, and they should not at any season be allowed to suffer for want of water at their roots.
If Acacias at any time get over dry at the roots, the foliage on the lower parts of the plants turns yellow and falls oft', thereby destroying their beauty. Repotting should take place the first year as often as the plants fill their pots with roots. It is not, however, desirable to continue the process after the first week of September; and by this time, if all has got on right, many of the plants raised from seed in the spring will be of a useful size for taking part in the general decoration of the establishment.
The second and future years once will be often enough to repot the plants, and this should be done early in spring. When repotting large plants of Acacias, use for a compost the best sandy loam procurable, adding thereto at the time a good sprinkling of bone-meal. Supply good drainage, and make the fresh compost firm in the pots when the plants are repotted. An occasional application of manure-water during the summer season to the roots is beneficial to Acacias, especially if they have their pots filled with roots, which is generally the case when the plants are large. During the summer season give them a thorough washing occasionally with the syringe or water-engine. This will keep red-spider and thrip under subjection, and otherwise be of benefit to the plants.
If green-fly appear, fumigate in the usual way; and if brown-scale or mealy-bug infest the plants, use the latter for fuel, and set about raising a fresh stock of plants from seed. J. Hammond.