Spring and summer allergies, brought to you by pine pollen

If you have spring and summer allergies, much of your discomfort is caused by the pollen from wind-pollinated grasses and trees. We think of pollination occurring as bees, butterflies and other insects, or bats visit a flower for nectar, then share pollen between flowers. But a surprising number of plants depend on their pollen blowing to the right place.

One of the interesting things about these plants is how they reproduce because they don’t make flowers as we generally think of them. They do have male and female reproductive structures, which are called flowers in grasses and cones in evergreen trees such as pine, spruce, and fir. In these evergreen trees, there are male cones which make the pollen, and female cones which produce the seed. You may have seen the male cones and not known what they were. But if you have been around pine trees in the early summer and seen the yellow clouds of ‘dust’ that blow off them, you know what the pollen looks like! 

Baby male cones full of pollen. They will expand to be a bit bigger and let their pollen loose in huge waves. Picture from http://www.statesymbolsusa.org/.

Male cones shedding pollen. Picture from here.

This is an energy-inefficient way of reproducing, having to produce large amounts of unused pollen in hopes that some of it will hit a fertile female cone of the same species. Insect pollinated plants are considered to be more efficient and advanced. 

Baby female cones: When they are this small, the pollen blows onto them and fertilizes the tiny seed-beginnings inside.
Image from http://forestry.usu.edu/.

Once the seed is fertilized, it will grow inside the expanding cone until the seed is mature. If it is nut-like, as in pinyon trees, the seed is heavy, and will fall out of the cone onto the ground.

Female pinyon cone with mature seeds. Image from Wikimedia.

Other needled trees produce seed that is winged and can be carried in the wind. Like the cone-bearing trees, male flowers of grasses produce lots of pollen to ensure fertilization of the female flowers and the subsequent seed development. In the grasses, the reproductive parts are not very obvious, but are quite interesting to look at if you have a magnifying glass. 

As a young plant geek, I stumbled upon the most breathtaking displays of flowers made out of glass at a museum on the Harvardcampus near Boston. A master glass-blower made flowers of exquisite beauty and amazing detail and this was my introduction into how beautiful the floral structures of grasses can be. It is easy to be impressed when they are displayed many times life-size and show the extraordinary detail that is hard to see with the naked eye. If you are any kind of a flower lover, you can spend hours and hours in this place. The picture below is one of the displays – a banana flower, made out of glass but so lifelike that it is breath-taking. If you ever go to Boston, check out this museum. It is one of the wonders of the world.

A banana flower made of glass at the Harvard Museum of Natural History. Image from Curious Expeditions's album Glass Flowers at the HMNH.

Anyway, I digress – back to pollen. Grasses flower on stems that look like seed, which they eventually will be. But before there are seeds, there are flowers, pollen – lots of pollen, fertilization, and seed development.

Blooming wheatgrass. Image from www.statesymbolsusa.org