I have two boxwood plants that are over 25 years old. The plants get an accumulation of brown leaves with webbing on the limbs & I usually brush the plants with a broom to remove. This spring one plant had mostly brown leaves and stems. I started cutting back all of the totally brown stems in April and some now have green leaves but the plant doesn't look well even with the green leaves. The other boxwood looks very green but has a lot of the brown dead leaves accumulating and a couple areas I have trimmed since they turned white. Both looked like the image 2112 last year. Any suggestions?
Yellowing and webbing on Boxwood can be caused by several factors. One common cause is the presence of spider mites, which are tiny pests that feed on the plant's sap and create fine webbing. Spider mite infestations can lead to yellowing of the leaves and overall decline in the health of the Boxwood. Other possible causes of yellowing and webbing include fungal diseases, nutrient deficiencies, and environmental stressors such as excessive heat or drought. It is important to identify the specific cause in order to implement appropriate treatment and prevent further damage to the plant.
Likely, it is one of two insects, and the lifespan of the shrub may be close to an end. They live around 20 to thirty years on average, but can live much longer with proper maintenance. Leaf miners and spider mites cause webbing, commonly. Neem oil and fungicides may be necessary.
These articles will offer some suggestions for these issues:
https://www.gardeningknowhow.com/ornamental/shrubs/boxwood/boxwood-spider-mites.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/spider-mite-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/azadirachtin-vs-neem-oil.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
My sprinkle system is working and I do not think it is a watering issue. I appreciate any help on this .
I do see what appears to be a darker soil near those two. It may be that the spot is slightly lower and holding on to water for longer. Soil that is not allowed to dry out will deprive roots of oxygen, while allowing for unwanted microbial life.
I would try and keep water from that area, or water the whole area less, as they can handle a slightly drier soil more than wet, though they prefer the area, only, slightly moist. Anywhere from 3 to 5 inches down should be dry before watering again.
For now, I would water with a fungicide, and follow the above. If you do not see new growth soon after doing so, then you might consider them to be replaced.
This article will help you with proper care:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/japanese-holly-care.htm
I’m removing a large boxwood hedge and would like to plant other shrubs in that bed. Should I let the soil rest or treat it with nutrients before planting new shrubs and perennials?
This will depend on results from your soil tests. Once you know what the soil needs, then you can begin to correct any issues.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm