When should I prune my holly bushes?
For shrub hollies, pruning is done in late spring or early summer after new growth has hardened off. Prune to shape as needed.
For tree hollies, the best time to prune is in the late spring. To encourage compact growth, pinch or shear the tips following the natural pyramidal shape. Resist the temptation to keep shearing once the tree has filled in and is growing well, unless your goal is a formal look.