River Birch trees typically drop many leaves in the summer for various reasons. They make many more than they need, and this isn't of great concern. 

Dogwoods can have multiple challenges (see here): https://extension.umd.edu/resource/key-common-problems-dogwoods/ but they generally tend to hold their leaves. Are they turning brown before they drop? Are they pretty healthy overall? Are you able to water in times of drought? They are shallow-rooted and appreciate a 3" layer of mulch to keep the soil more cool and moist. (Keep it pulled back from contact with the trunk).


Christine

Hello Tom,

A bit more information will help us determine what might be happening. Are you able to share photos of the dogwood's symptoms and the location in which it's growing? How long has the dogwood been in the ground (was it recently planted), and has this happened every year for a few years in a row? Does the tree otherwise flower and grow normally up until the shedding starts? Did anything change in the soil drainage of that area of the yard, like utility digging or re-grading, or the redirection of any nearby roof downspout outlet? Were any herbicides used on the lawn or plant beds nearby?

Miri

Thank you for the additional information and photos. Although the images are too small to magnify well, we can't really see any clear indications of why the trees might be stressed, though as Christine mentioned, drought is a typical stressor for both species, and we were quite dry during most of the 2023 growing season.

Could either tree have girdling roots at its base, or be planted too deeply? This may be more likely with fast-growing birch than slow-growing dogwood, but it's possible on any tree, especially if they happen to be mulched too heavily or if mulch or soil covers the root flare.

An in-person assessment from a certified arborist might be able to find root or trunk injury or sources of tree stress that are causing the premature shedding for several years in a row. Weather still could be playing a role, as would compacted soil if that part of the yard is walked-on regularly, but tree stress or trunk injury might have allowed a pest or disease to gain a foothold (more so for the dogwood).

Since the roots of each tree extend into the neighboring yard(s), it's hard to guess what conditions on that side of the fence are in terms of influencing tree health. (For example, maybe they weren't watering anything during dry weather, or they water too often for the dogwood's preferences, or an herbicide was used on lawn in that area of their yard, or digging was done for some reason that injured or killed some of the tree roots.)

Our plant pathologist doesn't see any clear indications of a disease, though says this type of pattern suggests that root stress or damage is likely. We do not suspect an insect issue unless it's a secondary infestation that arose after stress first weakened the tree, though the insects involved (while potentially present at the same time in each tree) would not be the same species between both dogwood and river birch.

Miri

You're welcome!