The most common pruning mistake we get called about is not bad cutting. It is good cutting done at the wrong time of year. Someone tidies up the shrubs on a mild winter weekend, everything looks neat, and then spring arrives and the azaleas produce almost nothing. Nothing was done badly. It was just done in February.
The principle behind the whole calendar is simple: some shrubs form next year's flower buds on growth made the previous season, and some form them on new growth in the current season. Prune the first group in winter and you are cutting off buds that are already sitting there, fully formed, waiting to open.
Spring bloomers — azalea, forsythia, lilac, viburnum, spring-flowering spirea, rhododendron, weigela, oakleaf hydrangea — set their buds the previous summer. Prune these right after they finish flowering, within a few weeks. That gives them the rest of the season to grow and set buds for next year. Cutting them in late fall or winter removes the flowers before they ever open.
Summer bloomers — panicle hydrangea, crape myrtle, butterfly bush, summer spirea, roses — flower on growth they make in the current season. These get pruned in late winter or very early spring, before growth starts. Cutting them back then encourages the vigorous new wood the flowers will appear on.
Hydrangeas deserve their own note, because they cause more confusion than anything else in a Tennessee yard. The big blue and pink mopheads are bigleaf hydrangeas and bloom mostly on old wood — cut them back hard in winter and you lose the season. The white cone-shaped panicle types and the smooth 'Annabelle' types bloom on new wood and can be cut back in late winter. If you do not know which one you have, the safe move is to remove only obviously dead wood and wait to see where flowers appear.
On crape myrtles specifically: the practice of cutting them back to thick stubs every winter is genuinely bad for the tree. It produces a burst of weak, whippy growth from the cut points that flops under the weight of its own flowers, and it permanently disfigures the branch structure that makes a mature crape myrtle worth having. They rarely need more than removing suckers, crossing branches, and dead wood.
Trees are a different calendar. Most deciduous trees are best pruned in late winter while dormant — the structure is visible without leaves, wounds close quickly as growth resumes, and disease pressure is low. Oaks in particular should not be pruned in spring or early summer, when fresh cuts attract the beetles that spread oak wilt. Dead, damaged or dangerous limbs are the exception to every rule: those come off whenever you find them.
Evergreens and hedges want shearing in late spring after the first flush of growth hardens off, with a lighter tidy in midsummer if they need it. One detail worth knowing: a hedge should be cut slightly wider at the bottom than the top. It looks counterintuitive, but a hedge that is wider at the top shades its own base, and the bottom thins out and goes bare within a few seasons.
Two rules that apply to everything. First, cut at the branch collar — the slight swelling where a branch meets the trunk — not flush against the trunk and not leaving a long stub. The collar contains the tissue that seals the wound. Second, if a shrub is badly overgrown, reduce it over two or three seasons rather than all at once. Taking a third at a time gets you to the same place with a plant that still looks like a plant in the meantime.
Not sure what you have or when it should be cut? We identify what is planted before we touch it. Call (940) 735-9667 for a free estimate.