Isn't it funny how allergies can just creep up on you over the course of your lifespan? Some people never have any allergies when they are younger. Then, all of a sudden, when they turn 30 something, they start getting the sniffles at the height of the spring season. Former Happy Camper, meet Mr. Pollen. Man, that is an introduction that you could have done without, right?
Along the same lines, it is not uncommon to hear examples of people suddenly developing a rash due to exposure to poison ivy plants, after traipsing through them for years with impunity. Some folks relate how, as children, they would laugh at the other kids who would warn them about poison ivy. To prove that the weeds posed no threat to their own health, they would even gleefully roll around in a patch of poison ivy. It was only much later in life that touching the dreaded "leaves of three" would have repercussions for them.
Of course, poison ivy is one thing, and air-borne allergens are quite another: The latter is much more difficult to avoid. But by choosing hypoallergenic trees for the plantings near your home, rather than their allergenic counterparts, you can cut down on your allergy problems. "Hypoallergenic" means "not likely to cause an allergic reaction."
What you must realize when discussing tree pollen allergies is that what we are really 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:
But, let's face it when deciding on a landscape tree, other traits must be factored in besides whether or not the tree is hypoallergenic. For example, just because a female Ginkgo biloba does not give off pollen, that does not necessarily mean that it is a great choice for your landscaping. They may not shed pollen, but they do shed a fruit-like product that makes them among the messiest trees that you can grow.
Of course, the primary factor in plant selection is, usually, simply whether or not we like the look of a certain plant. So what happens if none of the trees listed above appeals to your eye for beauty? All hope is not lost: Some monoecious trees are less allergenic than others. This is because not all pollen is created equal. The worst pollen for allergy sufferers is the type that has a fine texture. Coarser pollen tends to stick closer to home, rather than traveling around and launching attacks on the poor allergy-sufferer. Luckily, some of the best trees for spring landscaping produce just such a pollen. Examples of monoecious plants with coarser pollen are: