Question: I have two Santa Rosa plum trees planted in my backyard. One is planted in a lawn, and the other is in a rock landscape. Both are doing well with numerous large plums growing on them. The one in the lawn area has about 25 percent small yellow plums that fall off when I flick them or shake the branches. The remainder of the larger plums look great.
The small, yellow fruit that drop off easily when you gently shake the branch have not been pollinated. Maybe the bee didn’t get to that flower.
Even without pollination, the fruit will start to form but without a seed developing inside the fruit. Without the seed forming, the plum fails to grow, the fruit dies on the tree, and it is aborted. This is frequently normal.
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.