Tuesday, August 14, 2012

Adirondack Ragweed and Hay Fever Season

August is a month known for ripening raspberries and blackberries, the appearance of locally grown sweet corn and other fresh produce at farm stands, the return of back to school ads on TV, and the unwelcome arrival of hay fever season.

For many people, exposure to certain types of pollen triggers a most unpleasant nasal reaction that can linger for days. While the pollen of numerous plants contributes to this often severe irritation of the nose, sinus cavities and upper respiratory tract of many, ordinarily healthy people, ragweed is, by far, the leading culprit responsible for making life miserable for those unfortunate enough to be afflicted with this common medical condition.

Like many plants that are viewed by the general public as weeds, ragweed lacks colorful petals, or an attractive floral display. Rather, this plant that can grow to 3 feet high bears small reproductive structures that are as inconspicuous as they are unattractive. The leaves of ragweed have a shape that resembles the foliage of a marigold, and the plant generally develops numerous branching stems that give it a dwarf, shrub-like appearance.

In August, as the plant matures, clusters of tiny pollen sacs located on the ends of numerous spikes open and release many millions of pollen grains to the air. Unlike some wildflowers, like milkweed and clover, which rely on bees and other insects to transfer pollen form one plant to another, ragweed uses the wind. Also, once it matures and begins to produce pollen, ragweed continues to form these male reproductive cells until the plant is killed by a hard frost. This is why hay fever season extends from August until that time in September or early October when a large high pressure system from the north puts an end to the growing season.

Scientists have determined that a moderate breeze is capable of transporting ragweed pollen dozens of miles over land. Ragweed pollen has been collected over a hundred miles out in the ocean, however, wind conditions over the open water are quite different from those that occur across mountainous terrain. As moving air encounters the foliage of numerous trees and shrubs, some of the material being transported is eventually filtered out.

The seeds of ragweed are enclosed in a tiny, irregular-shaped burr designed to catch on the plumage of a bird that happens to perch on this plant, or the fur of a mammal, like a deer that brushes against it as it walks through the area. Eventually the seed pod is dislodged and falls to the ground where the seeds can lie dormant for decades until growing conditions become favorable.

Ragweed is a plant that thrives in open, sunny sites in which the competition for light and soil nutrients has been reduced. Fields that have been recently plowed, logging clearings in which the existing vegetation has been seriously disturbed or destroyed, and areas in which a building has been torn down or a section of a garden has been abandoned are all places in which ragweed is quick to sprout.

In the Adirondacks, ragweed may be encountered on the side of roads that are not regularly mowed by highway crews. The use of sand and salt in winter on roads creates fairly harsh soil conditions that limit the development of some forms of plant life close to the pavement. Ragweed is one of the few plants that can grow in this semi-sterile soil. Additionally, ragweed is able to survive in exceptionally dry soils and is able to gain a foothold in places during years when drought suppresses the growth of other vegetation.

The presence of maturing forests severely limits the growth of ragweed in most sections of the Adirondacks. However, there are various places in and around the numerous hamlets of the Park in which ragweed can be found. Also, ragweed grows in pastures and in other open sites around the periphery of the Park. Because of its presence in scattered locations throughout the Adirondacks, individuals that suffer from hay fever can still be impacted in many of our larger communities, although the severity of their allergic reaction may be less than that experienced in most other sections of the country during this time of year.

Recently, there has been some discussion regarding the presence of true wilderness in the Adirondacks. Most have centered on the impact of humans, or the proximity of roads, hiking trails and an ability to achieve solitude. I would suggest that the most remote location in the Park be defined at this time of year by the lowest measurement of ragweed pollen. This would certainly provide a most peaceful experience to anyone that suffers from hay fever.

Photo: Common ragweed, courtesy biosurvey.ou.edu

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Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

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