- Male cones on male trees produce cypress pollen. Cypresses produce pollen that drifts on the wind because the pollen is very light and dry. The whole gymnosperm group, including all of the Cupressaceae family, tends to be wind-pollinated: The wind carries the pollen from the male trees to the cones containing the eggs on the female plants.
- As cypress pollen is shed, the wind catches it and takes it into the atmosphere. Once in the atmosphere, the pollen carries hundreds of miles or more. In the northern hemisphere, cypresses produce pollen from late January into June. For many cold climate areas these are heavy snow months. As snow forms and falls, the pollen is caught in the flakes. Wind can also blow pollen onto the snow after the snowfall.
- Cypresses and their relatives -- junipers, redwoods and incense cedar -- grow in areas where it snows. In any location, the snow will not contain a large amount of cypress pollen that was produced by native stands of cypress several hundred miles away. Cypresses are planted as ornamentals, however, around the world, and that has increased the amount of cypress pollen found in the mixture of pollen dropped by wind, referred to as pollen rain.
- Before the mid 20th century, cypress pollen allergy was not common. During the last 60 years, it has become popular to plant cypresses as ornamentals. Many areas have extensive hedges of male trees that produce quantities of cypress pollen. Gardeners can limit the problem by choosing female trees or removing male cones by trimming trees as the cones are formed. Snow and rain also remove pollen from the air, decreasing the allergic response.
next post