At the bottom of my field is a large silver maple tree and nearer my house are two, 50 year old red maple trees. A few weeks ago I noticed that the branches of these trees were getting increasingly granular looking. These reddish, twig granules were the leaf and flower buds that were swelling with the rising tree sap. Within the next few weeks both the silver maple red maples will flower. They are among the first trees to flower in the spring.
The buds with which these trees encase and protect their embryonic flowers and leaves are very interesting structures. The outer part of the bud is made of tough scales which form an overlapping, shingle-like structure around the delicate leaf or flower growth tip. These bud scales keep out destructive insects and also insulate the inner tissues. These scales are really tiny, very tough, modified leaves.
Buds are classified as to whether they encase flowers (“floral” buds), or leaves (“vegetative” or, simply, “leaf” buds), or both floral and leaf embryonic tissues (“mixed” buds). The positions of the buds on a twig are also important with “terminal” buds being found at the end of a twig and “lateral” buds being found along the sides. On silver and red maple trees most buds are either floral or vegetative. The floral buds are larger and spherical and the leaf buds are smaller and more oblong. The floral buds are also typically clustered together in bunches on the twig. Over the winter I have watched red squirrels balancing themselves out on thinner and thinner branches of the red maples eating large numbers of the lateral buds. They were not able, though, to reach the terminal buds, so I expect to see both flowers and leaves concentrated at the ends of tree branches.
Soon (may only two weeks from now!), the floral buds on the silver and red maples will open and the delicate clusters of red and yellow flowers will cover the reddish twigs. The tiny pollen grains from these flowers will be spread by the wind and some will encounter ova in the ovaries of other flowers and accomplish the fertilization phase of the reproductive life cycle. The pollen is produced in prodigious amounts by these trees, and you can easily understand why. The probability of a given pollen grain, randomly being dispersed through the atmosphere by the wind, finding an appropriate ovum is infinitesimally small! To insure that fertilization occurs at all, the trees must fill the air with pollen. Human interactions with this pollen mass can generate allergic reactions in sensitized individuals. Hardwood tree pollen, in general, is a major spring allergy trigger.
Once an ovum is fertilized it will develop into the silver and red maple’s distinctive winged seeds (their “samara”). These “maple keys” will, by early May or so, form great, fluttering clouds as they drop from the trees and become scattered by the wind across lawns and woodlots. Some of these seeds will germinate immediately while others may lay dormant in the soil until the following year. But these seeds and seedlings are topics for a summer essay (and (great news!) summer is not that far away!)