I find this time of year to be one where it is easy to get pruner-happy. While most things can survive a poorly timed pruning, there are a few that will make you skip a year of beauty if you cut at the wrong time.
What can be cut now?
- old perennial growth
- dry branches and leaves
- old grass growth
- some fruit trees, vines--depending on whether they bloom on year-old wood
- old flower heads
What to avoid cutting now?
- Rhododendrons and azaleas: the buds were set in the fall and should only be pruned immediately after they bloom
- Forsythia -- wait until done blooming
- Hydrangea macrophylla (mop head hydrangea) -- except to remove old flowers. Wait until new growth comes on before pruning out dead
If in doubt, wait.