Gardening With Wattles
Acacias are generally grown from seed. Some of the smaller species may be propagated from cuttings. Seeds, because of their hard seed coat, require treatment before sowing. This usually entails either pouring near-boiling water over the seeds, or scarifying the seed coat (such as by rubbing between two pieces of glasspaper, or nicking the end opposite the aril), and then soaking in water. In one report (Ashford & Murray 1979) it was found that nicking the seed coat resulted in a 100% germination rate after one week as against a lower germination rate after 3-4 weeks using a 30 second boiling water pre-treatment.
Following such treatment some of the seeds will have swollen. Those that have not are not necessarily infertile. The seeds of a wattle plant, like the seeds of many other sclerophyllous plants, vary in the length of time they require to germinate in response to suitable germination conditions. This is an evolved safeguard against natural disaster. The seeds may be sown into a normal sowing mix, such as a 1:1:2 mix of washed sand:peatmoss substitute:sandy loam (Gardiner 1988). Germination may occur within several days and continue for some weeks. Spring and early summer appear to be the best times for sowing. Autumn and winter sowings tend to be slow to germinate and produce less vigorous seedlings, or fail to germinate. Successful germination may be had using immature (green) seed and sown without pre-treatment. This may be advantageous when the soaking of mature seed encourages fungal growth. The use of dry heat and microwaving of mature seed can also be used to alleviate these problems, but care is required especially when using microwave treatments.
Following germination, the seedlings should be potted up without excessive root disturbance. As most species occur in infertile soils, fertilising should be done cautiously. Generally a low phosphorus, slow release fertiliser is preferred when considered necessary. Many of the species from arid areas produce, quite quickly, extensive root systems, and for such species planting out should not be delayed.
Propagation from cuttings may not give satisfactory results. Half-ripened wood, taken in spring to early summer is generally regarded as the most dependable (New 1984).
Most wattles prefer a sunny position in a light, well drained soil. However, many are quite adaptable in their light and soil requirements. Many are also drought tolerant and are hence useful in dry areas. Frost tolerance is variable. As a general rule, species from the coastal forests and woodlands are less tolerant of dry semi-arid conditions, and conversely, those from the dry interior do not generally tolerate high humidity.