Georgics 2.362–370

362And while their first youth grows with new leaves, the tender things must be spared; and while the shoot pushes gladly into the air, let loose with slack reins through the clear sky, it must not yet be tried with the edge of the pruning-hook itself, but the leaves must be plucked with bent fingers and thinned here and there. 367Then, when they have embraced the elms with sturdy stems and shot up, then strip their foliage, then clip their arms — before this they dread the steel — then at last exercise hard rule and check the straggling branches.