Allergy Trees – Trees you can live with and Trees you can’t

By Steve Nix

Plants that produce wind-blown pollen, many of them trees, make life miserable for millions of human allergy sufferers each year. A large number of tree species produce extremely small pollen particles from their male sexual parts. These trees use the wind as their favorite means of pollen transport to others of their own species for pollination. This pollination leads to procreation of new trees.
Pollination is critical for trees to reproduce but can be crippling to some people with specific tree allergies and asthma. If these allergy sufferers live in areas with lots of the wrong trees, there can be major health issues and loss in quality of life during the peak pollen season.

Allergy sufferers can make it through tree pollen season with a minimum of discomfort by following some common sense suggestions.

Minimize outdoor activity between 5 and 10 a.m., as morning is the time when pollen counts are usually the highest. Keep the house and car windows closed and use air conditioning to stay cool. But you don’t have to stay inside all the time either.

You need to have an awareness of the kind of trees you live near or the trees you plant that produce small-sized pollen. Certain trees can become a major allergy problem. It is your understanding of this, in combination with a knowledge of allergy producing trees, that can help make the difference between an itch and sneeze-free day or a day of complete misery.

The Major Allergy Trees

I have searched the literature and found that there are a number of trees to avoid if you are allergy-prone – and they are not necessarily a single species but usually a single sex. The allergen that triggers your allergy is produced only by the “male” part of a tree. Trees vary widely in their capacity to produce and disperse pollen and trigger allergies and asthma.

Some tree species that bear separate male and female flowers on the same plant are called “monecious.” Examples include honey locust, oak, sweetgum, pine, spruce, and birch. You can’t do much but deal with these as a species.

“Dioecious” tree species bear male and female flowers on separate plants. Dioecious trees include ash, boxelder, cedar, cottonwood, juniper, mulberry, and yew. If you select a male plant you will have problems.

From an allergy perspective, the worst trees you can live around are dioecious males, which will bear only pollen and no fruit or seed.

The best plants in your environment are dioecious females as they bear no pollen and are allergen-free.

Trees to avoid are male ash, pine, oak, sycamore, elm, male boxelder, alder, birch, male maples and hickory.

Things you can do to avoid a problem:

  • Plan your landscape – Minimize exposure to known allergens by not planting or totally eliminating certain trees from your yard.
  • Plan your time outside – In order to minimize exposure, plan outdoor activities to coincide with times when the pollen count is lowest.
  • Keep up with the pollen count – Follow the local pollen index (the number of grains per cubic meter of air) that will alert you to days when your particular allergens are most prominent.
  • Allergy skin testing – Using the scratch or blood test for allergies can help you determine what type of pollen allergies you have.

Allergy Friendly Trees

Obviously, the fewer allergenic trees in an individual’s immediate vicinity, the less the chance of exposure. Good news is that the great majority of windborne pollen grains of all species are deposited quite close to their source.

Remember, a pollen producing tree or shrub next to a home can create ten times more exposure than a tree or shrub one or more houses away. Get those high risk trees away from you home.

One rule of thumb – flowers with large blooms usually produce heavy (large particle) pollen. These trees attract insects that transport pollen and do not depend on wind transportation. These trees are generally lower in their allergy potential. Also, “perfect” flowers on trees are desired. A perfect flower is one that has both male and female parts in a single flower – not just male and female parts on the same tree.

Trees that are considered to cause less allergy problems are:
Female ash, female red maple (especially the “Autumn Glory” cultivar), yellow poplar, dogwood, magnolia, double-flowered cherry, fir, spruce and flowering plum.

Reproduced with permission

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