Q.Holly Bush
I planted a Holly Bush (I believe it’s a Blue Princess variety) about 18 months ago. It has grown a little bit since then and is now about 4 feet high. It gets direct sun for a few hours and indirect light for many hours. About 8 months ago, I noticed that the bush was looking sparsely folliated. I noticed a broken branch which is surviving after being taped back in place. I began to notice leaf drop with marks on the branches where the leavers were. The leaves are dropping from the MIDDLE of branches not the bottom or top. The fallen leaves look ok on the underside but the tops have light brown colors mixed into the green (splotches). The soil seems to get good drainage and the plant gets water. There is no sign of insect infestation or feeding. I live on Long Island, N.Y. The climate has been somewhat unpredictable and at times unseasonable, but at least part of the winter is harsh, but seldom hitting zero degrees F. The Holly has received liquid fertilizer and epsom salt in it’s water, separately, about two times each. Only once since planting has there been just a VERY few red berries (6 or less). Why is my Holly not keeping it’s leaves?
Hollies are expected to lose some leaves in spring or summer, but in a healthy plant these leaves will be quickly replaced, so the bush won't look sparse. If the holly is located in a poorly drained/wet area, the excessive water around the roots could cause leaves to yellow and drop off. Here are a couple other potential causes to look into:
https://www.rhs.org.uk/advice/profile?PID=175
https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-yellow-leaves.htm