Hello Sue,

There are a few possible causes of stress or damage that brought the tree to this condition. Abrupt weather changes (like late-spring frosts we've experienced in past years, or cold snaps after mild winter weather), drought stress in hot summers (if not irrigated), soil health, and other factors can cause lack of vigor or dieback of existing branches.

There is older scarring visible on at least one major branch. This injury is sealed (trees don't heal like cuts on our skin do, but this looks as "healed" as it can get) but caused the loss of some sapwood, which feeds smaller branch growth and foliage. There is no treatment which will reverse this loss. Therefore, portions of the canopy cannot regrow in these areas, though it might be able to be hidden over time from nearby healthy stems. Trees have multiple points from which they can put out new growth, so these dormant buds can take over when a limb is lost or damaged. On a tree with more branches we'd normally recommend such a badly-damaged branch be pruned out, but here that would take too much canopy away as well as ruin the shape of the tree aesthetically. If you decide to do it, the plant can still recover it's canopy if it's otherwise in good health, but it will take time as Japanese Maples tend to grow more slowly the older they get.

The fabric that looks like weed barrier ("landscape fabric") may be causing more problems than it solves; removing it would be ideal, though we don't know how practical that will be if the tree's roots have entangled in it. Maple roots do tend to grow fairly shallowly, and mulch that has broken-down into organic matter on top of the fabric over the years may now be harboring roots that grew up into it as well as underneath. At the very least, it should be pulled/cut back far enough from the trunk that it leaves several inches clear of fabric, or just remove what you can piecemeal. Horticulture is still studying the effects of weed barrier fabrics, but it is thought that they impede moisture and oxygen levels in the soil, which can harm beneficial soil life (and root health), which in turn can reduce the vigor of desirable plants. If you can remove it without tearing-out too many maple roots, try doing so.

Japanese Maples benefit from even levels of moisture during hot, dry spells. This tree's location gives it a bit more reflected heat from the brick and concrete, so check on its watering needs weekly during summer. The plants that are used in the pots around its base may also be robbing the tree of some needed moisture if their roots get into the surrounding soil, though mulching this bed does help minimize evaporation overall and helps keep the soil cooler. Some diseases, including one which causes stem dieback and cankers (like the branch scar), have greater success infecting plants that experienced drought stress. Once an infection has set in, there are no treatments except to keep the rest of the plant as stress-free as possible by irrigating when needed.

An arborist likely won't have any intervention suggestions or abilities beyond the above, but if you wish to look for one, the second and third links on this page provide search tools: https://extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree

Miri

You're welcome, and thank you.

This page on watering trees and shrubs may be of use come summer (and into autumn) when we tend to experience dry spells: https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs

Here is a blog post about Japanese Maples from a few years ago that may also be helpful, though not all of its points made will be applicable here: https://marylandgrows.umd.edu/2018/08/24/japanese-maples-in-maryland-landscapes-plant-location-care-are-keys-to-success/

Miri