health of srubs
When you have several different species with similar problems, there are usually some environmental/cultural issues that are affecting them. Diseases and insects are also attracted to stressed plants, so it vitally important to match plants to the best location for them (sun/shade, wet/dry, etc.)
Several cultural/environmental issues that could be negatives:
- shearing the plants. This can be stressful and over time creates very tight foliage that does not dry well after rains and thus fosters fungal problems.
- We suspect that the soil is clayish and does not drain well, this keeps plant roots too wet for too long. The holly may have a root rot. The yew also. We recommend replacing them.
-The mugo pine has a fungal disease known as diplodia. Very common. They all tend to get this eventually and it is not easily treatable. It's already far gone. Needs to be replaced.
- The Alberta spruce probably has spider mites. This is common for them in hot dry conditions. (They are native to Canada.)
Finally, the mulch appears to be very deep. We recommend no more than 1-2" in depth, and mulch should never be piled up against the base or trunk of shrubs and trees. It encourages insect and disease problem. Also, voles like to hide in it and gnaw bark and roots. Pull back the mulch and check for vole holes and tunnels.Here's help on controlling voles: https://extension.umd.edu/hgic/voles
Because this shrub bed is below a window, replace these shrubs with ones that grow slowly and stay low without pruning.Read plant tags very carefully for ultimate height (in 10 years? with annual pruning?). If the tag is not very helpful, go online for better info.
There are many dwarf varieties of evergreen that would be suitable. Some are semi-evergreen, such as abelia, but have nice flowers. Dwarf spirea is another good choice for flowers, though it is deciduous. Some shrubs, such as Weeping English Yew, have a growth habit that stays fairly low but if a branch gets too high, use hand pruners to remove it. Avoid shearing. A few snips here and there will give your shrubs a more natural look, not stress them, and be much less work, and also keep the foliage more open to allow better air circulation.