Many of our silver (Acer saccharinum) and Freeman maples (A. x freemanii) are looking a little more open and thin at the tips of their canopies. The foliage in the lower, interior of these trees is dense, but when you look up at the tops of the trees, the leaves appear fewer and there are noticeable gaps at the base of the new shoot. This is not an insect or disease problem, but the combined action of two different agents: 1. late frost and 2. a heavy spring seed crop.
Frost Damage
The late frost we experienced in early May resulted in freeze injury to many maple leaves as they were expanding. Maples, particularly silver, red and their hybrid, the Freeman maple, were just leafing out during this time period so they took the brunt of the damage. Trees spared were the basswood, which leafed out earlier and thus had fully expanded, not as tender leaves, and the bur oak, which still had its leaves in the buds. The frost injured maple leaves have black margins around most of the leaf and these damaged leaves are beginning to fall. The ground beneath some trees is almost completely covered with these frost injured leaves. The partially defoliated trees are beginning to put out new leaves and within a month the damage will be less noticeable.
Heavy Seed Crop
You may have also noticed visible gaps beneath the foliage on the tips of the shoots and the older, interior leaves. This gap is where the maple flowers and fruit occurred this spring.This year a fairly heavy seed crop occurred on maples and the “helicopter” seeds were observed by many maple tree owners. These seeds are now littering the ground, sidewalks and gutters. Many of the more commonly planted Freeman maples such as Autumn Blaze (A. x freemanii ‘Jeffersred’) generally produce few flowers or only male flowers but not always. Even on trees that are considered males, seeds can occur in some years.
