Hi, 

This is a large and old Boxwood shrub. There are likely several overlapping factors that led to this state. Boxwood are susceptible to many different disease and pest problems, including one called Volutella blight which is a condition that can affect the roots of the shrub and in turn cause die back or the foliage and branches. Too much long-term shearing that created a dense outer layer of foliage and dead inner branches is a common issue for these plants as well. Proper pruning is needed to reduce plant stress and for the longevity and health of  shrubs. Also, potentially recurring drought stress in years with a deficit of rain due to its proximity to the tree with root competition as also likely a factor. 

You can try to do some drastic renewal pruning to remove the dead branches and see if it can make a come back. It will take some time for it to regrow, if it does. It could start coming up from the roots and base of the plant instead of the older branches. Then you would just need to make sure to keep it maintained in more of a natural, open growth habit. The fall isn't the right time of year to prune boxwood because you will stimulate new growth that will suffer from winter freezing temperatures and cause more dieback. You can remove the old dead foliage and branches, but in the spring you could perform more of the renewal pruning for the healthy portions of the shrub, to even up the appearance and see if that will help to stimulate new healthy growth. 

The other option is just to remove it. The newly free garden space could be a nice change for some native shade plants and heading into the fall is a great time to plant for some fun changes next spring!

You can explore the following webpages and videos to learn more about common boxwood issues, proper pruning, and some native plant replacements if you are interested. Should you have further questions, please feel free to continue to reach out. 

- Emily

https://extension.umd.edu/resource/boxwood-identify-and-manage-common-problems - the bottom of this page has a video on how to prune boxwood

https://extension.umd.edu/resource/why-include-native-plants-your-garden

https://extension.umd.edu/resource/recommended-native-plants-maryland