The answer to 'why is my shrub mud' is that your shrub likely has poor drainage, causing the soil around the roots to become waterlogged and muddy. This can happen due to factors like heavy rainfall, improper irrigation, or soil compaction.
Some common symptoms of a muddy shrub include wilting leaves, stunted growth, and discolored or mushy roots. To fix this, you'll need to improve the drainage around the shrub. This may involve aerating the soil, adding organic matter, or installing drainage pipes or a French drain system. If the issue is severe, you may need to transplant the shrub to a better-draining location.