We know it’s April in Virginia when our car changes color under a coating of yellow pine pollen. The finger-writing on the car’s hood on the second day of pollen fall soon disappears under new layers, like the first footprints in snow vanish under fresh falls.
This event coincides with our peak allergy season, but don’t blame pines just because they produce the most abundant pollen. Their grains have a couple of bladders for buoyancy needed for wind pollination. But large size prevents them from descending deeply when we breathe, and, equally important, their smooth surface isn’t sticky. Easily blown off the hood.
Pine is an exception among wind-pollinated trees (and grasses) that are responsible for most seasonal allergies. Trees like birch and alder, and species of oak. Their grains are smaller, so they descend deeper down our windpipe, and sculpted or wrinkled surfaces stick to mucous membranes. Birch seems an exception to the rule until you notice the smooth triangular grains have points that make them prime allergy triggers too.
We are hardly affected by pollen transmitted by insects, birds, and bats. Maple, cherry, hornbeam, dogwood, tulip poplar etc.
Each pollen grain looks like a work of art under the scanning electron microscope. Their forms are unique to the species, which makes fossilized grains valuable in ecoarcheology.
That raises the question why? Like so much in biology, the answer is natural selection. Wind-pollinated grains are produced abundantly to ensure some land on female targets that match their contours, and small enough to drift far. On the other hand, animal-pollinated grains are adapted by co-evolution between the plant and animal vector for sticking to particular wings or feathers, etc.
Admire the beauty of the pollen story when you stop sneezing!
Roger musing about Peace with Nature 