Tree Notes is about trees -- especially native trees, trees for wildlife, and trees in history.

Monday, October 12, 2009

Ginkgo tree on Google Hot Trends

Smelly ginkgo seeds are a curiosity and a problem.

A week ago today, I brought my morning coffee to the computer and sat down to read the news. One website led to another, and before long, I was taking a look at Google's Hot Trends -- a list of the top 40 search terms of the past few hours.

Usually when I glance through the Hot Trends, I don't know what or whom most of them are. (I don't keep up very well with "popular culture", as my son calls it.) So, I was surprised to see a familiar name on the list -- "gingko tree". Yes, the tree Ginkgo biloba was one of the top 40 Hot Trends of that moment.

Why did the curiosity of thousands of internet users focus on the gingko tree at about 7:00-8:00 A.M. PDT on October 5, 2009? I think I can guess. Two headlines from Google's list of ginkgo-related news articles and blog posts offer a clue:

As the female ginkgo tree dresses herself in the beautiful yellows of her autumn habit, foul-smelling seeds mature and drop to the ground. It is ironic that these two events coincide.

The seeds are about the size and color of wild yellow plums. The odor of the fleshy part of the seed is often compared to rancid butter (both contain butanoic acid) or to feces.

Technically, the ginkgo tree's seeds are not fruits. The gingko is classified as a gymnosperm because it produces naked seeds. The squishy, smelly part of the seed is a fleshy shell that covers the harder life-containing center of the seed.

A standard solution for the seed problem has been to plant male ginkgoes. Male trees produce pollen-bearing cones. It is interesting that the pollen contains motile sperm (sperm that can move themselves). The sperm fertilize ovules on the branches of female trees. Fertilized ovules develop into seeds.

It is unusual for gymnosperms to be dioecious-- that is, to have separate male and female plants as the ginkgo does. Ginkgos have a latent ability to be monoecious: male ginkgoes sometimes start producing seeds, foiling the best-laid schemes of landscapers and homeowners.

Various (male) cultivars have been developed and are available through nurseries. Or, you can grow your own ginkgo tree from seed. But please don't plant ginkgoes where the seeds will ever be a problem -- even if you're starting with a male tree. Plant them in a place where you can see and enjoy the unique beauty of the tree -- but a place where you won't smell or step on the seeds, if the tree ever produces them.

4 comments -- please add yours:

DRB said...

Interesting -- those in Memphis have just turned bright yellow.

Genevieve said...

I love seeing ginkgo trees in the fall. The leaves usually become a very true shade of yellow.

As you know, I don't often write about non-native species of trees, but I made an exception to the rule for ginkgoes because I like them. :)

Eastcoastdweller said...

One possible side effect in urban areas of planting only male trees to avoid the mess and stench of fruit, has been a major increase in pollen, causing more torment for allergy sufferers.

Genevieve said...

"Male cones ripen to release pollen when female flowers are receptive – usually in March to early April. Ginkgo pollen is a light, buoyant spindle shape when released. Ginkgo pollen can generate a number of allergy problems during the short time it is on the wind. "

Source: "Identification & Silvics of Ginkgo", Dr. Kim D. Coder, School of Forest Resources University of Georgia

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"The power to recognize trees at a glance without examining their leaves or flowers or fruit as they are seen, for example, from the car-window during a railroad journey, can only be acquired by studying them as they grow under all possible conditions over wide areas of territory. Such an attainment may not have much practical value, but once acquired it gives to the possessor a good deal of pleasure which is denied to less fortunate travelers."

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Print references I frequently consult

Benvie, Sam. Encyclopedia of North American Trees. Buffalo, NY: Firefly, 2000.

Brockman, C. Frank. Trees of North America: A Guide to Field Identification. Ed. Herbert S. Zim. New York: Golden, 1986.

Cliburn, Jerry, and Ginny Clomps. A Key to Missouri Trees in Winter: An Identification Guide. Conservation Commission of the State of Missouri, 1980.

Collingwood, G. H., Warren David Brush, and Devereux Butcher. Knowing Your Trees. Washington: American Forestry Association, 1978.

Dirr, Michael. Dirr's Hardy Trees and Shrubs: an Illustrated Encyclopedia. Portland, Or.: Timber, 1997.

Elias, Thomas S. The Complete Trees of North America; Field Guide and Natural History. New York: Book Division, Times Mirror Magazines, 1980.

Grimm, William Carey. The Book of Trees;. Harrisburg, PA: Stackpole, 1962.

Hightshoe, Gary L. Native Trees, Shrubs, and Vines for Urban and Rural America: a Planting Design Manual for Environmental Designers. New York: Van Nostrand Reinhold, 1988.

Little, Elbert L. National Audubon Society Field Guide to North American Trees. New York: Chanticleer, 1996.

Martin, Alexander C., Herbert S. Zim, and Arnold L. Nelson. American Wildlife and Plants. New York: McGraw Hill, 1951.

Mitchell, Alan F., and David More. The Trees of North America. New York, NY: Facts On File Publications, 1987.

Randall, Charles E. Enjoying Our Trees. Washington: American Forestry Association, 1969.

Settergren, Carl D., and R. E. McDermott. Trees of Missouri. Columbia: University Extension, 1995.

Sternberg, Guy, and James W. Wilson. Native Trees for North American Landscapes: from the Atlantic to the Rockies. Portland: Timber, 2004.

Wharton, Mary E., and Roger W. Barbour. Trees and Shrubs of Kentucky. Lexington: University of Kentucky, 1973.

Wyman, Donald. Trees for American Gardens. New York: Macmillan, 1965.

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