Wednesday, April 25, 2012

The Understory of Dogwoods

Those recent 50 mph winds here in Grand Rapids ripped through the Redbuds and spattered their flowers over the ground. Just as these magnificent pink blossoms (see: Redbuds Revisited) are fading and falling, the Flowering Dogwoods are next to enter the Spring spotlight.



You may be fortunate to have one in your landscape, or you may see them arching from the edge of the woods as you drive the country roads.


The native Dogwood (Cornus florida) lives as an understory tree, growing between the lower shrubs and the upper tree canopy...

                                        ...growing slowly in these open, but shady areas.

It grows 15' - 30' in height, is short-trunked, dividing low, with slender  spreading branches forming a flat-topped crown.


In SW Michigan, the Flowering Dogwood reaches its northern limit in our Grand River Valley. Found in Oak and Beech-Maple forests.

These spectacular white blossoms you are viewing are not blossoms!



Botanical truth: these are four, white notched bracts that resemble petals.

That cherry-colored notch on each bract used to be a bud scale; a protective winter covering for the future flower.



These showy white bracts, conspicuous from a distance, attract insects for pollination.



The true flowers are in the center. Greenish-yellow and tube-shaped before opening.
                                                                        About 20 - 24 per cluster.


         Try to recall your Biology or Botany classes. These are bisexual flowers -
 having both male and female sex organs; also called a perfect flower.



Look closely here as the first flower curls open like a tiny trumpet. Examine the cluster. Can you guess which will be next? Notice the four filaments with an anther at the tip of each one. The anthers will soon develop pollen. The shorter, sticky stigma awaits to receive the pollen. Sex in these trees relies mainly on the bees.

Dogwood leaves are arranged opposite, as opposed to alternate. Their petioles (leaf stems) are short and grooved.



Dendrology students know the "M-A-D-Horse" acronym: Maple - Ash - Dogwood - Horse-chestnut... tree families with opposite leaves.


                                            Leaves are clustered at the ends of slender twigs:
                                          
                                          Within the leaves, find the nicely curved, parallel veins.


                                      Look at all the parts bursting forth from one terminal bud!


How to age a tree twig? In this next photo:

  • Start from where the twig divides into two
  • Count each half-inch segment: 4 segments = 4 years growth
  • Newly emerging pair of leaves = 5th year, for that twig's age



References


The Book of Forest and Thicket
John Eastman
Stackpole Books  c 1992
 

Michigan Trees - Charles Herbert Otis
University of Michigan Press - Ann Arbor
c 1931; 16th Edition c 1965

I purchased this for a Dendrology class in 1967. A Dogwood leaf
is still pressed on page 237. It's 45 years old!


This piece was detailed and infused with Botanical terms. I believe the most miraculous thing about these intricacies of God's nature, is that it all works!




 Annie Dillard states this in her usual eloquent fashion:

"These are mysteries performed in broad daylight before our very eyes; we can see every detail, and yet they are still mysteries."

Pilgrim at Tinker Creek (Pilgrim)
c 1974