In vacant lots and neglected parks, residents are planting trees — lots of them, close together.”Tiny forests,” which originated in Japan, are popping up across Canada and around the world. …In total, about 600 trees and shrubs — blue beech, swamp birch, balsam fir and two species of oak among them — were planted in an area about the size of a tennis court. That works out to three trees for every square metre of land. …Todd Irvine, a Toronto arborist said in certain situations tiny forests make a lot of sense, such as in areas sorely in need of tree cover. In 15 to 20 years, however, he says “there’s going to be a significant amount of horticultural maintenance, because some of those large trees are going to be shaded out and they will begin to die. Really fast-growing trees can have structural consequences. You’ll get these really large, quite frankly, spindly trees.”