N E W S & V I E W S • A P R I L 2 0 2 4 15 dependent on early season planting (before December shut-down) and a hardening off period before the first extreme frost. What are the negatives of planting clones? The main one is windthrow, because they are established from cuttings the root development is slower which can lead to young trees falling over; from experience it is worth providing support to such trees with stakes. Purchasing clones established in the ellipot system and planting them slightly deeper than seedlings also seem to reduce the risk of windthrow. The other negative is the cost of the clones (R4 000 more/Ha more than seedlings). However, one must consider the increase in both timber and bark, to make up the difference. Green wattle is another option to consider. Both NTE and UCL have done bark tannin trials during the past wattle season and have agreed to accept limited quantities of bark from green wattle. However, black wattle remains the preferred bark source and we don’t recommend converting this species but rather consider suitable pine or eucalypt compartments. Green wattle can withstand up to 3˚C colder temperatures than black wattle, providing you plant early in the growing season. This means in cooler areas where in the past you may have planted species such as E. dunnii, could be converted which could increase your NSV by up to R20 000/Ha. Silviculture recommendations Planting at the correct spacing and thinning to ensure the optimum stocking at rotation end has a significant impact on your final timber and bark yield. Seedlings should be planted at a spacing of 3 x 1.5m which is 2200/Ha and thinned down to about 1 500 stems when the trees get to about 7m-9m (1 400 stems on dry sites). It is important while thinning, to ensure that all dead, diseased, deformed, and weaker trees are removed. Clones can be planted at 3 x 1.8 which is 1 800/ Ha and allows for some mortality and windthrow. Pruning of wattle is an important silviculture operation as the relatively wide planting escapement promotes the growth of side branches. Insect damage and browsing may also increase the amount of forking. This is a simple operation which is frequently carried out incorrectly. The object of pruning is not to prune minor side branches for producing knotfree timber as is done for pines, but rather to improve the form of badly shaped trees. Wattle is extremely susceptible to disease infection through wounds and over-pruning is a serious risk. Use a small team of skilled labourers and close supervision is essential. Trees should be pruned before they are 2m tall. All basal shoots and the weaker leader forks should be removed using secateurs. Basal forks which are too large for secateurs should be removed with a small bowsaw, not with an axe, tearing of bark must be avoided. Always leave a stub of 20 to 30cm long to prevent the entry of disease into the main stem. Pruning during winter is preferable as the incidence of disease is lower. Serious insect or climatic damage may necessitate this step being carried out again. Although wattle is a hardy and robust crop, it is very sensitive to management practices. If the right genetic material is planted wattle can yield over 20 tonnes of bark and 100 tonnes of timber at nine years of age if it has been properly planted, fertilised, weeded, and thinned. Good genetic material together with recommended silviculture will result in uniform high yielding compartments.
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