Ash Flower Galls Many homeowners become alarmed when they see
green or brown clusters hanging from branches on their ash
trees. The clusters are ash flower galls and do not harm the
tree. Most ash trees are dioecious – that is, the tree has
either all male flowers (staminate) or all female (pistillate)
flowers. Early in spring, a tiny eriophyid mite, Eriophyes
fraxinivorus, feeds on the tiny male ash flowers. Ash flower
gall mites are too small to be seen without the aid of a
magnifying glass. The ash tree, in response to the insect
feeding, grows tissue around the insect. As a result, the
flowers enlarge and stay on the tree for up to two years,
instead of dropping off the plant during the first spring. The
galls are green at first, but become brown later in the growing
season. Research has shown that the galls do not harm tree
vitality, though they can be considered unsightly. In extremely
rare situations, the weight of galls can cause branches to be
strained. The tiny mites (about 2/100 of an inch long) sp