Today, tree of heaven is widespread in almost all of Slovenia. Due to the problems it causes to the economy and the environment, it must be eliminated in some places. In landscape park Tivoli, Rožnik and Šišenski hrib we tried to remove the tree of heaven by three mechanical control treatments, which are: pulling, as well as breakage of annual and biennial shoots. The studies results have shown, that the best treatment was total removal by pulling seedlings and saplings. The other two methods, still do suffice, but are not as effective. In the plots, where we used method of breakage of biennial shoots, sycamore maple best reached higher height classes. In the control plots, the Ailanthus altissima outgrew native species that were not competitive. We also found that the growth of tree of heaven was less intense below a forest canopy than in the gap.