If ash trees don't have a central trunk but have grown with a Y trunk from 15 foot or so from the base, which has then developed further off shoot branches not resembling the asymmetrical appearance, what can be done to help the tree? Also, when the ash tree doesn't have a straight trunk but has distinctive changes in direction of growth, should these be reduced in height to help develop a stronger tree growth? I have several Ash trees that are over 50 foot high, which do not reflect the appearance of a healthy rounded canopy with a central straight single trunk, and a couple have grown at an angle and I'm concerned that they may fall if not given the proper care.
An Ash Tree should be trained to grow with a central leader and pruning is needed to ensure that they have a strong structure; as they have opposing branch structure.
Ash Trees are susceptible to several diseases and pests, so proper pruning technique is very important.
Broken, dead and damaged branches are removed to help maintain tree health.
Living branches can be pruned to improve sunlight exposure and air circulation.
I would certainly invest in having the tree inspected by a certified Arborist to determine the tree health and if the tree could be pruned to a more pleasing appearance.
I myself have several large Ash Trees on my property that were never pruned and grew into multi branching trees. The side branching does lead to a weakened tree and we have had extensive damage during storms to these trees. We are going to have these trees removed from our property due to their weakened state.
I will also mention that a mature Ash Tree will benefit from fertilizer. Feedings of a organic-based macro and micronutrient fertilizer will help them sustain their health.
You should be able to locate a product specifically formulated for Ash Trees.