Naturespeak A naturalist's view of the world

January 13, 2009

The Bark of a Winter Dogwood

Filed under: Uncategorized — wykes @ 5:11 pm

Spend anytime outdoors during the winter and you are liable to get red-faced. You’ll slip on the ice in front of your neighbor and embarrass yourself, scream at that plow driver who just scraped a load of snow across the end of your freshly cleaned driveway, or slowly loose the feeling in your nose and cheeks as you work to clear off that newly deposited load of snow. Getting flush is a natural emotional and physical reaction to the world around us. I guess you could say it makes us human, except for the fact that we are not the only living beings to get red in the wintertime. Red Osier Dogwood twigs do it too.

Now, before you get all red-faced with indignation at being equated to a stick, let me say outright that dogwoods do not possess souls and are not a threat to our identity (If you are a Druid, please ignore this remark as one made by an ignorant non-believer). These common dogwoods are  low, multi-stemmed shrubs found throughout our landscape. Like all dogwoods, they have an opposite budding and branching growth habit, but they are best identified this time of year by their bright coral red, or burgundy, stems.

It’s not necessary to take a closer look to appreciate them, but if you do (see here) you’ll see that the smooth shiny bark  has a gem-like quality. You will notice many raised ovals, called lenticels,  that pepper the  finish.  These serve to provide a white contrast to that marvelous background color.  At this point, you might be thinking  that this bark is probably just as red during the summer as it is during the winter so my point is pointless. Actually, however, this is not the case. Young Red-Osier twigs turn scarlet in the fall and stay that way through to the following spring. Around these parts they take on their red hue during the first half of October. Before that time, the branches are dull reddish purple to gray.

This dogwood species is a favorite for landscape plantings because it adds a splash of color to an otherwise colorless season. One horticultural variety, developed by the Minnesota Landscape Arboretum, is called the “Cardinal” because it produces an especially bright scarlet winter bark. Native basket makers have learned to collect the mid-winter twigs and use them just like willow twigs for basketry. The name “Osier”, by the way, is derived from the French term for  “Willow-like.”  “Dogwood,” for those who like complete thoughts, is believed to be a corruption of “daggerwood”  but no one really knows. “Red” means exactly what it says.

It is a singular and somewhat incredible fact that the Red-Osier turns red during the winter. Part of the reason for this pretty conversion has to do with a chemical change in the wood itself, but the explanation is not pretty. This species is considered to be one of the most freeze tolerant plants known. Scientists have been able to bring the temperature down to -269 degrees C (the same temperature as liquid helium) without killing it. I wonder if the scientist who made that observation announced his discovery with a really high voice due to the effects of the helium?  That would be embarrassing wouldn’t it!  Anyway, the mechanism works like this. The shortening days of autumn prompt the dogwoods to lower their stem water content and subsequently increase the amount of a chemical known as 24 kD protien.  This protein has something to do with the incredible freeze tolerance of this plant and probably stimulates the “red-effect.”

I wish I could say that the 24 kD protien is red colored and therefore directly turns the bark red, but I would be barking up the wrong tree to do so. Other dogwoods have this protein as well, but apparently not to the extent the Red-Osier does. This is why I say “red-effect.”  This word is derived from the French for “I don’t really know, but there is a connection.” Let’s just say this dogwood has a nice bark and be done with it.

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