Yew trees that are turning brown and appear to be dying can look like this for a number of reasons; namely cats and dogs, drowning, root rot, salt and honey fungus. Yew trees typically have a reputation for being indestructible so if any of these factors are causing your Yew tree to turn brown, it is very likely that it can be revived back to health quite easily and quickly.
Excrement from cats and dogs can contribute towards your Yew tree turning brown. Where one cat or dog goes to the toilet, many others tend to follow. Try to discourage animals from using the toilet near the base of your Yew tree in the future.
It is possible to kill Yew trees by drowning. While they can live in practically any soil, if the roots are submerged in water for a long period time it can kill them. Avoid planting Yew trees in a trench, instead choose soil that has good drainage or create the drainage yourself.
Root rot is evident in all soil but it will thrive and affect your Yew tree in the right conditions. To try and prevent root rot from affecting your tree, ensure that the soil has good drainage and enrich the soil with organic matter to encourage root growth.
If your Yew tree is planted near a wall or road on which salt is used to remove snow, the salt content of the water running off the wall onto your Yew tree could cause it to turn brown. Avoid planting your Yew tree close to salt run off points.
Although Yew trees are rarely affected and killed by Honey Fungus, it is still possible. Honey Fungus penetrates the tree from underneath so by cutting off any broken bits of root and improving the soil with organic matter, the fungus can be avoided.
Each of these factors could be the cause of your Yew tree turning brown.
Experiment with ways to treat the tree until you find the best way to bring it back to life.
