Reprinted from The EnvironMentor, vol. 10, no. 4, pp.9-10
Achoo! Spring pollen season is upon us.
Here in Oklahoma we're not just afflicted by what grows (and sheds its pollen) nearby. Our spring winds can bring allergens from far distant places in all directions! It's the fault of plants that depend on wind to carry pollen from the “male” flower parts of one plant to the “female” parts of another. (Wind-born pollens are smaller and lighter than those that depend on animal pollinators.)
Wouldn't allergy sufferers be more comfortable if we could get rid of those pollen-shedding males?
FOLKTALE “The Disappearance of the Giants”
Long ago in northern Africa, cattle-herding peoples puzzled over piles of stone blocks on the grasslands. These looked like rubble of fallen buildings – but the stone slabs were huge! The elders explained them with a legend about a nation of giants who had once lived there.
They said the giants were cattle herders like their normal-size human neighbors, but were so large that they used a tree trunk for a spear handle, and an elephant hide for a water skin. They could each eat one cow a day! And so their herds were enormous, swarming over the grasslands and drinking up the waterholes. When humans tried to defend territory for their own herds, the giants fought them off.
The elders said that God began to regret having made the giants, and finally spoke to their leader. “I have decided that your tribe is taking more than its share of this land. You can't stay here any longer: your time on Earth is over.”
The giant's leader complained, “We are only defending what we need to live. You made us the way we are, it's not our fault!”
“That is true,” replied God. “So although I won't change my mind, I will send you away with kindness. You may choose: do you want to go with my blessing, or my curse?”
“With your blessing, of course.”
“Very well. Since sons are a blessing, from now on your wives will bear only boy babies. And since female cattle are more valuable for their milk, from now on your cows will have only female calves.”
The giant chief was delighted. This blessing sounded wonderful! The next several years, the giants rejoiced with the births of their sons and female calves.
But as the heifers matured, after a while there were no bulls to mate with; and so no more calves were born. And as the boys grew into manhood, they found no giant maidens to marry.
The giants' herds dwindled until there were hardly enough to feed the surviving bachelors. Realizing their fate, these old giants pulled up slabs of rock and built tombs for themselves. With their last strength they crept inside and shut themselves in.
There is nothing left of the giants now but their fallen tombs, the elders say. And when you see the rocks, you may be reminded that too much of a blessing can be as bad as a curse.
City planners and urban foresters want the blessings of trees to soften our town landscapes. But they don't want problems with trash (seed pods), vermin (fruits attracting rodents and birds), or odors (esp Ginko fruits, which smell rotten). So they often choose tree species that are dioecious (“dye-ee-shus” = two households, that is, pollen comes on “male” trees, seeds and fruits on separate “female” trees). And they plant only the males.
Good deal! The wind takes care of pollen disposal! But sometimes wind borne pollen is so thick that it clouds the air, covers the landscape, and triggers some really rotten allergies.
One of the worst culprits in these parts is mountain cedar (Ashe juniper, Juniperus ashei). Pollen from its male trees blows from Texas into Oklahoma when we get a south wind, and some people react so strongly that it's called “cedar fever” with flu-like body aches in addition to the usual head-cold-like symptoms of pollen allergy.
Examples of other strictly dioecious trees include other cedars (Juniperus species), cottonwood, and yew. Some that are usually dioecious include ash, boxelder, mulberry, and maple – but occasional individuals may be monoecious (having both male and female on the same plant).
[To tell the truth, pollen from some monoecious species can be equally troublesome. Honey locust, oak, sweetgum, pine,spruce, and birch are all wind pollinated. I recall an oak-surrounded parking lot where all the cars turned the same yellowgreen in spring.]
What would be another disadvantage of growing just one “sex” of a tree? Unlike the Giants (or their cows), trees don't have to mate: people can root cuttings of the desired male/female parent plant to reliably reproduce what we want. But in avoiding the problems of female fruit, some cities have created a problem with pollen allergies.
“The Departure of the Giants” (Favorite Folktales from Around the World – Jane Yolen, Pantheon. Pp 352-3
The Crest and the Hide and other African Stories – Harold Courlander, 1982 pp 97-99