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Word of the Week: Whorl

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Welcome to Word of the Week! Stay tuned for a new word each Friday to amp up your nature vocabulary!

Word of the week is Whorl [hwurl] (botany noun): An arrangement of similiar parts (sepals, petals, stipules or branches) that radiate from a single point and surround or wrap around the stem of a tree or plant.

When the ground is covered in a blanket of white snow, we can always count on the deep green colours of the High Park evergreen trees to bring that contrasting pop of colour.

Many evergreen trees, like pines, spruces, and firs, have whorled branches that form a circular pattern around the growing tip. Each whorl represents one year of growth, which means that counting the number of whorls can help us determine the age of these trees, especially for young evergreen trees.

Here are some tips for counting whorls to determine the age of an evergreen tree (according to Open Oregon Educational Resources):

  • On most trees, the lowest tree branches are systematically dropped as the tree grows and the sun no longer hits the base of the tree. Therefore, when estimating age using this method, it is important to include the bottom-most stubs and/or knots where it is evident branches once existed.
  • Two to four years should be added to most species to allow for the time between seedling germination and evidence of branch whorls on the trunk
  • Small single branches between major branch whorls do not constitute a true whorl or year of growth. Do not count these false whorls.
  • A very short increase in length between whorls that seems unlike the other years’ growth may indicate a “lammas” year, in which the tree flushed twice, often in response to extraordinary growing conditions. Ignore those years unless it is evident that some injury is responsible for the very short internode

This method of “counting the whorls” usually works very well up to fifteen years of age. One really has to get close to the tree, look carefully for evidence of bud scars, and know the growth habits of these species.

On your next Winter visit to High Park, we would like to encourage you to find a young evergreen tree and try to determine the age by counting whorls.

Resources: https://openoregon.pressbooks.pub/forestmeasurements/chapter/4-4-field-technique-tips-for-counting-whorls/

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