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All photos provided by Rainbow Treecare Scientific Advancements Developing a strong structure is important at this age. Maintaining size and monitoring for decay is important at this age. particularly during the drought-laden months at the end of summer, can be a lifesaver for middle age trees.Trees that suffer from drought are more likely to suffer from secondary pest problems, deplete their stored energy reserves, and not restock those reserves as their photosynthetic abilities are greatly reduced. How much water do these trees need? There are plenty of complicated formulas one can find, but an easy one to pass on to homeowners is five minutes per DBH", three times per month from April through October.That means a 12"DBH tree should have the hose on for one hour, about every 10 days during the growing season. Old trees See the section on middle age trees. Mulch Young, middle age and old trees We can lump all three age classes together here because the recommendation remains the same regardless of how many growth rings the tree has.The improved growth of roots under mulch, particularly when compared to root growth under turfgrass,is well documented.As an organic mulch layer is closer to the surface of the forest floor than a well groomed lawn, this makes sense. Mulch, however, has a diminishing return on investment the thicker it is applied. We've all see "volcano mulching" going halfway up the trunk and know that is downright harmful to a tree, so keep it about 2" deep.While you can go too deep with mulch, you really can't go too wide. How wide should a mulch ring around a tree be? I'll defer to Dr.John Ball who is quoted as saying,"Show me the property line, and we'll negotiate inwards." www.arborage.com Pruning Young trees Besides getting a newly planted tree's roots established, pruning young trees for proper development is probably the most important thing that can be done at this stage of life. Trees with poor structure are more likely to fail and become hazards later in life.To develop a strong structure,follow these simple guidelines from Dr. Larry Costello: 1. Remove dead, dying, damaged, diseased branches. 2. Select and establish the central leader. 3. Select the lowest permanent branch (LPB) based on tree location/purpose. 4. Select and establish scaffold branches. 5. Select temporary branches below the LPB and remove or head back others. Middle age trees While much of the structural development should have taken place during the tree's formative years, there are still plenty of reasons to trim a middle-age tree,but any removal of live tissue should have a clearly defined objective.Reducing the risk of failure,improving structure,improving aesthetics, providing clearance, improving vista views, and even reducing the amount of shade the tree is providing are all legitimate reason to prune a tree. The amount of live tissue that should be removed from a tree in a given growing season is not unlimited, so be judicious in how much trimming you do.A general rule for middle age trees in good health is not to remove more that 10 to 15 percent of live canopy per season; removing more than this slows root growth by shifting the root to shoot growth ratio.This adds significant stress to the tree.Heavy pruning also reduces carbohydrate reserves,making the tree less tolerant of insects, diseases and drought stress.If the tree is stressed or declining,pruning is not recommended until the tree recovers and resumes normal growth again. Even a modest sized mulch ring can benefit trees of all ages. Old trees The same rules apply when pruning an older tree that were Arbor Age / October 2013 15