Elder Wildwood learned that the hard way. They all did. The Greenwood tribes have had to deal with a lot during their time occupying these vast deciduous forests, taking care of it. The magic here was unsuitable to ponies, who could not intuitively control the growth of the plantlife nor sooth the hearts of the wildlife that made its dwelling here. It would not be commanded, but nor was it like the wild land of the blighted Everfree to the west where magic roamed as it wilt. Rather the magic of the Hartwoods was mischievous, recalcitrant, playful at times.