Western Red Alder Pollen
Transmitted Off Crossed Polarized Light Illumination

Western Red Alder, Alnus rubra, pollen is an oblate periporate (typically 5 pores) grain with distinctive pore structure. Alnus rubra has a relatively high frequency of 4 and 6 pore grains as can be seen by the 4 pored grain in this image. Alder is a prolific pollenater and in the coastal Northwest United States is frequently found in airborne samples from early January to late February. It can often be used to indicate the presence of dust reservoirs or time since last through cleaning in an indoor environment.