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Male plants are not to blame for allergies
By Laura Whelan
MISSISSIPPI STATE -- A recent theory claims extensive use of male plants in the landscape is the culprit behind the sniffles and sneezes of allergy sufferers, but many gardening experts believe such planting practices are not to blame.
Thomas Ogren, a California-based author and former host of the radio show "Thomas Ogren's Wide World of Plants," is the main proponent of the theory that an overabundance of male plants is increasing allergies. He claims that because female plants produce debris like seeds, seedpods and fruit, most cities choose to plant "litter-free" male clones. Since male plants produce pollen, Ogren says this overplanting has resulted in more airborne pollen and an increase in allergy problems.
"This theory is primarily limited to desert towns in the West, an environment that is almost pollen-free to begin with," said Cecil Pounders, research horticulturist with the Mississippi Agricultural and Forestry Experiment Station. He said most tree-pollen allergies in the South come from its extensive hardwood forest, which includes oak, hickory, juniper and cypress.
Pollen is produced by the stamen, a plant's male reproductive organ. Male flowers release pollen, and females receive it to reproduce sexually.
"But the pollen problem isn't necessarily caused by male flowers," Pounders said.
"A male tree or plant will contribute to allergies depending on its natural pollination system, whether it is wind-pollinated or insect-pollinated," Pounders said. "If the system depends on insects for pollen movement, very little, if any, pollen will blow around and affect people.
"On the other hand, if pollination is achieved with the help of the wind, it matters little if the plant has perfect flowers (with both male and female parts) or just male flowers, because nature blankets large areas with pollen to ensure pollination," he said.
The researcher based at Mississippi State University's Coastal Research and Extension Center in Biloxi said the male plant theory does not account for the diverse plantings of the eastern United States. In the East, large numbers of male clones of trees or shrubs are not needed because many varieties thrive naturally in the region. Pounders also said many of the most common trees, shrubs and vines in this area have few male forms available.
Some gardeners believe that removing male plants, recognizable by their lack of stigmas or undeveloped stigmas, and replacing them with pollen-free females, which have well-developed ovaries and stigmas and lack developed stamens, will reduce allergies.
"This practice is an attempt to micro-manage gardening in a world where nature practices macro-management," Pounders said. "Windborne pollen is still going to travel into the house and yard through the air."
Pounders said gardeners have a better chance of reducing the effects of pollen by planting insect-pollinated, rather than wind-pollinated, species in the landscape. As a general rule, plants that have brightly colored, attractive flowers are insect-pollinated. Their heavy pollen sticks to bees and butterflies and is not likely to become airborne.
"People are going to have allergies; we will not escape that," Pounders said. "But gardeners can take a realistic approach by trying to decrease their number of wind-pollinated species to prevent pollen in the air."
Many allergy sufferers think strong-smelling plants like privet and honeysuckle are responsible for their allergic reactions. But Pounders said a strong scent does not mean the plant has released more pollen.
In fact, it is more likely that the strong smell itself produces sneezing or headaches. If these plant odors are bothersome, Pounders recommends moving them away from property boundaries to avoid the scent.
Contact: Dr. Cecil Pounders, (228) 388-4710