Remedial Pruning
Damage Control After the Big Snow Job
By Rachel Foster 1/22/04

Last month's snow did plenty of damage to trees, shrubs and hedges around town. Pines, old arbor-vitae hedges and broad-leafed evergreens were hit particularly hard. Trees and slow-growing rhododendrons that lost big limbs may be slow to recover their beauty. If the main structure remains intact and seems worth saving, the best thing is to remove all the damaged branches at their origin on the trunk or a sound limb, shape up what's left as best you can, and be patient.
Many a broad-leafed evergreen shrub, however, will recover quickly and more uniformly if the whole thing is cut back to a low framework of sound woody stems. February and March are good months for this kind of remedial pruning, whether you are repairing storm damage or simply bringing an old laurel or overgrown Mexican orange blossom back in scale with the garden.
When a hedge of some coniferous plant like arbor-vitae or hemlock gets too big for its boots (or sustains serious snow damage, for that matter), there is really nothing to do but remove it, because most conifers (redwood and yew being notable exceptions) will not sprout from old wood. Coniferous hedges need annual pruning to keep them useful over a long lifetime. Other hedges benefit from regular pruning too, but many broad-leafed evergreens, especially the laurels, hollies and photinias most popular for hedges, are more forgiving, and even huge specimens can often be re-habilitated by radical pruning.
Over-grown English (or cherry) laurel is a good example. These days, gardeners and landscapers are more likely to plant a dwarf or slower-growing cultivar of Prunus laurocerasus than the kind with big, shiny oval leaves that can grow to 30 feet, but even dwarf laurels get too big eventually. Cutting back your hedge or screening bush to stumps once in a while will bring it back in scale and make it much easier to prune.
Hedging plants are deliberately chosen for their vigor and quick growth, but they are not, of course, the only evergreen shrubs that grow too big. They are not the only evergreens that tolerate drastic pruning, either. Camellia, choisya, native Oregon wax myrtle and evergreen huckleberry, skimmia, leucothoe and most evergreen viburnums can all be cut back hard with a reasonable expectation that they will spring right back again. Strawberry arbutus, wax myrtle, ceonothus and escallonia will occasionally be killed to the ground by severe winter freezes and rise again within one to two years. This behavior tells you that they will probably survive drastic pruning, too.
Rhododendrons vary in their response to pruning. I would get expert advice before cutting down a tree-like specimen and expecting it to grow back from the stumps. If the main stems look nice and stand up unaided, it is often better to prune away the lower growth and plant something else underneath. Lax-stemmed, bushy rhodies that have a tendency to lie on the ground or contain twisted, intertwined interior stems are another matter: They usually respond well to hard pruning.
The best time to cut back any shrub really hard is late winter or early spring. Plants are all set for growth at this time of year, and they should respond by making a lot of strong shoots that will continue to grow until mid-summer, then harden up before winter. Drastic pruning later in the year might result in the same lush growth, but there is a risk that the soft new leaves will be scorched or shriveled by intense sunlight, and summer growth may not have time to mature before cold temperatures arrive. October freezes are not uncommon, and they can kill soft growth that developed late in the season.
To ensure timely re-growth after you prune, it is a good idea to feed plants lightly now and again in late spring. Don't feed later than June, however, because you don't want to encourage continued growth too late in the year (see above). Make sure heavily pruned shrubs get plenty of water through the first summer, and if you are pruning something that is under the eaves or on greedy tree roots I would begin watering right after pruning.