Hi, 

These are Boxwood shurbs which are different than Box Elder, which is a type of tree in the maple family. 

The yellowing of leaves could be due to various ailments. You can read through our Common Problems of Boxwoods page to explore management. 

Often, root stress due to overly-wet or poorly-drained soils either causes leaf damage outright or predisposes the plant to other issues that can cause yellowing, browning, or leaf loss. This looks like it could be a combination of winter browning from cold, or dry/frozen soils and also a Volutella infection. Volutella is a fungal infection in the branches and cannot be cured once present, though in some circumstances, fungicides can be used to suppress spread and protect still-uninfected growth. Treatment is only practical if most of the plant is still healthy, however, and should be a last resort (short of just replacing the plants instead). This is partly because treatment does not always work, sprays tend to require regular re-application, and spray residues might harm pollinators or other organisms. Although the degree of vulnerability to pests and diseases can be cultivar-dependent, the need for treatment in general may indicate that one or more environmental conditions are not allowing the boxwood to thrive and resist significant infections or pest outbreaks on its own. For example, they could be stressed if planted near your house wall, which reflects or retains heat in summer, as well as reduces air circulation through the foliage.

For now, trim out and dispose of the dying stems and consider thinning the remaining branches for better airflow, as this helps prevent or slow the spread of foliar diseases. (Manicured plants that are regularly sheared into dense, even shapes are more disease-prone.) If too much growth is browning and dying on any individual plant – say, a third or half of it – it may be too late to salvage the plant as the extent of symptoms implies too much damage has already occurred. An alternative would be to drastically cut back all growth in spring and force the shrub to regrow; if the roots are still healthy, this can be a successful way to rehabilitate a plant whose top growth has declined markedly or whose shape has become unappealing.

The past few years we have been mostly in drought conditions throughout the state. Have you watered in the times of high heat and drought? Stressed plants can more readily contract disease issues, so checking for supplemental irrigation is important to keep the plants healthy. 

Unfortunately, many evergreen plants can be slow to show symptoms of a problem, where the underlying stressor actually occurred some time ago. You can see if the trimming of the dead/dying/mostly yellow branches helps to slow any further die back, but if the plants look too sparse, you may want to consider replacing them, since it could take some time for them to fill back in. 

If you choose to remove and replace with boxwoods again, look for disease-resistant cultivars that are becoming more widely available in garden centers. 

Let us know if you have further questions. 

Emily