Sunday, March 29, 2009

Why Dogwood Flowers Catch the Eye

The dogwoods are out! Three decades ago we learned what that meant as only living in Atlanta can reveal. Now they are at it once again here in our home in North Carolina.

Of course the answer to the question includes dogwood's early appearance in spring before many other flowers are out and when few leaves have yet emerged. Spring sunlight filtered only by naked branches highlights both white and pink varieties of Cornus florida. Dogwoods filling the gap under a canopy of larger trees show the typical layered growth of a sub-canopy species, spreading branches horizontally so leaves capture the greatest amount of the limited supply of the sun's photons that penetrate deep into the forest. Before the leaves emerge, the showy flowers often mimic the green layering to follow, creating waves of white and pink.

But the dogwood's "flowers" consist of more plant parts than the typical flower. Those showy "petals" started out as four green bracts that enclosed an inflorescence, a bunch of the dogwood's tiny green flowers. As the bracts unfold they reveal 10 to 20 or more of C. florida's real flowers, the tiny green knobs collected at the center of the bracts. Each of these flowers will open, and small insects will spread pollen from the four anthers of each flower to the pistil of other flowers. The resulting fertilization of ovules will lead to the bright red berries each containing a single dogwood seed this fall. Each dogwood inflorescence can produce one to several berries.

The U.S. Forest Service maintains a page with all the botanical information you could ever want to know about dogwoods here:

Visit this interesting site for a complete photographic sequence of dogwood flowering and fruiting:

Thursday, March 26, 2009

Purplish Delights

This is a redbud, known to scientists as Cercis canadensis. It is a small tree, one of the first to flower in early spring, they are out now in Raleigh. Its other common name is Judas tree. Redbud is a member of the legume or bean family, the Fabaceae, and like all members of this family, actually enriches the soil it grows in. Legumes have tiny nodules on their roots designed to provide ideal habitat for nitrogen-fixing bacteria. These bacteria have the unique ability to capture nitrogen gas from the atmosphere and convert it to a form of nitrogen that the redbud, and any other plant, can take in through its roots as fertilizer. They generally make more of this fertilizer nitrogen than their host plant needs, and the extra enriches the soil for later plant growth. And since plants cannot take in nitrogen from the air, this is a very good thing. So besides providing an absolutely stunning splash of purple, redbuds are also good for the soil.

Tuesday, March 24, 2009

Among the first flowers!

Longer days and warmer temperatures open up opportunities to observe nature coming alive. Share your reactions to this view of bluets, found in Cary, North Carolina. Do you suppose bluets are insect-pollinated or wind-pollinated?

Saturday, March 7, 2009

Reckless George

The News and Observer in Raleigh published this letter, which I will reproduce here.

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George Will demonstrated reckless disregard for the whole truth in his two recent diatribes against the science of global warming (Feb. 16 and Feb. 28). His tactics border on dishonesty, choosing which facts to report and which facts to omit to best make his case.

The Arctic Climate Research Center makes clear in the statement Will cites that although global sea ice area has recently increased, Northern Hemisphere sea ice area has continued to decrease. Will may hope that few of us will actually go and read this statement, for once you do you realize that climate scientists predicted that sea ice area in the Southern Hemisphere is expected to increase before it decreases due to global warming, offsetting the expected (and observed!) sea ice area decreases in the Northern Hemisphere.

This is exactly what is happening, providing further confirmation that the climate scientists' predictions about global warming are not only scary, but accurate.

Denis DuBay