Treemagik creates very nice trees, and they look great. To use it you would first have to generate a trunk and open the trunk menu by simply clicking on trunk, and add trunk, for me it always seemed to hide the tab once i would click on it, but none the less it will generate a standard "default" trunk. After which, you would generate branches, and twigs, then create the leaves, all of which can be adjusted to suit your needs. And there are many textures to use too. Hope it helped a little.
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