Notes: Don't trim any plants (including trees & shrubs) that set their flower buds in the fall (ex: lilacs) until after flower unless you don't want/expect flowers this year. Also, Maple trees will weep sap if trimmed early in the spring. While this doesn't hurt the tree, you can wait until after the sap is done flowing if you are worried about it.
|Rabbit damage on Nanking Cherry bush|
Here are some general guidelines to remember when trimming shrubs & trees:
1) never remover more than 1/3 of the plant a year
2) trim the top narrower than the bottom so that the bottom branches don't get shaded out and die
3) remove any damaged areas (ex: snow/critter damage) - a fresh, 'healthy' cut is less likely to get infected
4) remove any branches that are rubbing the bark off another branch; these places become entry points for infection if left
5) be careful not to trim too deep on juniper or cedar; if trimmed beyond the green area they won't grow back
6) when trimming fruit trees remove any 'waterspouts' - branches that shoot straight up into the air; these don't bear weight well
These are some general guideline. If you are looking to shape a tree for landscaping architecture or for fruit production you will want to get some more specific information.