What you must realize when discussing tree pollen allergies is that what we are talking about, at least indirectly, is tree sex. The purpose of male pollen is to pollinate female plant parts. Sometimes, this process takes place within the scope of the individual tree (that is, there are separate male and female components contained within the same plant, in which case the plant is dubbed “monoecious”), but, other times, a species will have separate male and female plants. These species are referred to as being “dioecious.”

Why is it important to know this? Well, you can be sure that female plants in dioecious species will not give off pollen (because it is the role of the male plants, only, to produce pollen). That makes them the ultimate hypoallergenic trees. The following list reveals some examples of dioecious trees; simply grow female plants from this list in your yard, and you will minimize your allergy problems:

• Acer rubrum ‘October Glory’ 
• Aspen (Populus tremuloides), cottonwood, poplar, and related trees
• Boxelder (Acer negundo)
• Cedar (Cedrus)
• Juniper (Juniperus virginiana)
• Maidenhair (Ginkgo biloba)
• Mulberry
• Swamp tupelo (Nyssa sylvatica)
• White ash, green ash, etc. (Fraxinus)
• Yew (Taxus)