In general, trees have a long breeding cycle and are not suitable for amateur breeders . But selection within existing populations is possible. For example, most of the five-needle pines in North America have been killed by white pine blister rust. Those that survive are likely to be resistant and they merit study. Similarly, selection of the fastest growing gum trees is possible in areas that depend on firewood for cooking. The main species used in plantation forests are divided into softwoods and hardwoods. The principle softwoods are various species of pine, spruce, fir, and larch,. The principle hardwoods are species of gum trees, beech, birch, poplar, and teak.
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