Spring means pollen, lots of pollen coating our cars and porches in an ugly yellow film. It’s produced primarily by trees that depend on the wind to disperse it and comes from most conifers, such as pines, spruces, and firs, and from many broadleaf trees such as cottonwoods, oaks, ashes, elms, birches, and walnuts.
Red maple flowers — insect- or wind-pollinated. Flickr Creative Commons/Martin Labar
Trees take a big reproductive chance by throwing their pollen to the wind, but various strategies increase their chances of success. The hardwoods usually flower before the leaves come out to block the pollen. The pollen-producing male flowers tend to occur in long, drooping catkins to increase dispersal, and most of these trees are high up in the canopy where their pollen is more likely to catch the wind. To further ensure success, the trees produce huge amounts of pollen — as many as 10 million pollen grains from one cluster of birch catkins, for example; most of them land somewhere other than the intended female flower.
Other trees spread their pollen via partners — mostly insects, but also birds and bats. These trees need to produce much less pollen, but they do reward their pollinators with nectar as an energy source and pollen for protein. These tend to be understory trees with relatively large and sometimes fragrant flowers. Their pollen may be sticky rather than dust-like. Insect-pollinated trees include apples, basswood, cherries, black locust, catalpa, holly, horse chestnut, tulip tree, and willows.
Red maples are the first trees to flower — just look up. This is one of the most adaptable native trees. They grow in many soil types and in conditions ranging from wet to dry. Some trees have male flowers, some have female, and some have both on the same plants with the relative proportion changing from year to year.
These trees may also be wind- or insect-pollinated, probably another adaption because of their huge range, from Newfoundland to northern Florida. The wind blows everywhere, but fewer insects are found farther north in early spring, so using both methods is like having an insurance policy.
Oak tree producing pollen.
So after you have taken your antihistamines and are out washing the pollen off the porch, remember that you have experienced one of nature’s amazing strategies for reproduction. In the grand scheme, cleaning up the pollen is a small price to pay to witness this amazing spectacle.