English Yew Tree losing needles
I have an English Yew Tree that is several decades old. It reaches to 30 or 40 feet tall above my Baltimore City urban courtyard. When we moved in two years ago, it was dark green healthy. I have installed a rock garden underneath the tree during the past two years. This season starting in May, the tree lost a large amount of needles, turning dark yellow. New needle growth appeared in the end of the branches (see picture), but they really have not pushed forward. Recently, with the extreme heat in July and now the drenching rains, the needle health has quickly and desperately turned brown/yellow. Plus the needles seem to have shriveled - like they are not plump. How do we save this tree before we we pass the point of no return?
Since the main change to its environment has been the rock garden, it seems likely that may be the cause of its problems. However we would have to see photos of the rock garden to give a better diagnosis.
That said, we see no disease or insect issues, which does point to a cultural/environmental problem. Yews hate "wet feet" i.e. soil which does not drain well or stays soggy/saturated for long periods. It's non-intuitive, but stone groundcovering actually keep soil wetter than mulch/natural ground covers. It's posible that wet soil has led to the yew's root rot or disease, which means the roots cannot get water and nutrients up to the tree. If a lot of damage has occurred, the yew cannot recover. If there is enough root left, and the problem is addressed, then it may survive.