Tree Sex
Now that we have your attention:
Male dominance in the urban forest may be having profound and unforeseen consequences. A preference for male-clone trees over the last few decades has genetically manipulated today’s urban and suburban landscapes, creating an overabundance of male trees spewing pollen that may in turn be exacerbating allergy and asthma problems, according to Thomas Ogren, a gardening expert in San Luis Obispo, CA.
Most trees are monoecious, that is they have both male and female parts. However, many popular trees used to landscape homes and city streets like cottonwood, green ash, and maple to name a few are deoecious, which means they come in separate sexes, either male or female. The females produce fruit, berries and seeds that are pollinated by the males and therein lies the problem.
Many people consider that fruit or seeds dropped by the female trees to be annoying litter. In response, growers have cultivated male-cloned tress in many popular deoecious species that nurseries advertise to customers as litter-free, Ogren says. The “Cottonless Cottonwood” is a prime example of one used quite a bit in our area. The result is a male dominance in the landscape that has completely skewed the natural balance of the sexes among trees. Not only do more males mean more pollen, but also fewer females mean less fruit and seeds which are natural “pollen traps”. One cannot refute that allergy symptoms are on the increase. Asthma rates have sky rocketed. A very intriguing theory indeed.
|
