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Ragweed vs. Golden Rod
AAIA Quarterly - Volume 30 Spring 1994
Many people do not know the difference between ragweed and golden rod. Golden rod is a flowering plant designed by nature with bright colours and showy petals to attract insects. Insects transfer the male component of reproduction (pollen) to the receptive female organ (stigma). These heavy grains of pollen are not in the air. People do not breathe them in and become allergic to them.
(Webmaster note: Use Google Images to see the difference between these plants)
Ragweed does not have pretty flowers. It uses the wind to carry its pollen grains. Wind pollinating species compensate for this less precise transfer of sex cells by sending clouds of pollen into the air, and because of this, individuals are constantly exposed to these varieties of pollen and become allergic to them. More people are affected by ragweed than all the other species of wind-pollinating plants because ragweed is one of the most potent allergens and has the longest season.
The pollen of ragweed is only 1 / 2500 of an inch in diameter, but it causes trouble far beyond its size. Not only are there hundreds of varieties, but it is estimated that more than 250,000 tons of ragweed pollen is blown across North America each autumn. A single plant can produce about a billion grains of pollen. Just 4-5 grains is all that is required to cause symptoms in an allergic person. A ragweed pollen grain, under the microscope, looks like a battered up little golf ball.
Early in the morning, between 4 and 6 a.m., the tiny floret (which is a flower stripped down to its bare minimum to expose its pollen grains to the wind) is ready to release its pollen. The floret swells slightly and projects out. The petals which have been tightly closed over the sacs slowly open. Then the pollen sacs slowly open and the pollen is exposed to be picked up by the wind. All this takes about 30 minutes. By 9 a.m., most of the pollen has been given off for the day. Much of the pollen stays around the plant and is never wafted away by the wind. Some travels a short distance but some, carried by air currents, can soar 5000 or even 10,000 feet into the air, floating hundreds of miles in the wind.
Most plants respond to climate and pollinate when it is warm enough, so pollen times vary from year to year and from place to place. Ragweed, the worst cause of allergy, begins pollinating about August 10 – 15. Ragweed is unique because it responds to the amount of light vs. dark, so its pollination time is predictable year after year. The ragweed pollen season peaks around Labour Day (beginning of September) and lasts until the first frost in mid to late October.
Ragweed is known as a “pioneer plant”. It is usually the first plant that grows after earth has been disturbed for any reason. It is a rather pretty plant, but blends into its natural habitat so well that people seldom notice it.
Reference: based on “Pollen and Pollen Allergy” an essay by Dr. Christine Rogers.
Additional note by Webmaster- from Dr. Ham Pong’s list of cross-reaction between foods and trees:
Foods associated with RAGWEED pollen allergy
- banana, melons (cantaloupe, honeydew, watermelon)
For further information, see the article on Oral Allergy Syndrome
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