Due to yesterday's rainstorms, my plans for the day were cancelled. During a break in the rain I took a trip to a local park that I had not visited yet this spring for wildflowers. My first stop in this park is a Shrub Swamp located directly off a paved trail. Less than 10 foot off the trail I located this clump of dogwood. There are several species of dogwood located in Mid-Michigan and they can be difficult to identify at times. I took several pictures and moved on - I assumed the shrub was a Silky Dogwood (Cornus amomum) and expected to confirm this identification once I got back to the office.
|Dogwood leaves and flower|
|Closeup of leaves and flower|
Once I got back to the office I started looking at the photos and pulled out The Shrub Identification Book by George W. D. Symonds (William Morrow & Company, 1963). This book had become my go to guide for identifying shrubs. I expected to quickly confirm my initial identification as a Silky Dogwood. The first thing I looked at was the arrangement of leaves on the twigs - opposite. This didn't help, Silky, Gray (C. racemosa) and Red-Osier Dogwood (C. sericea) all have opposite leaves.
If the shrub had been bearing fruit it would have been easier to confirm. Red-Osier and Gray Dogwood have white fruit. Silky Dogwood has blue fruit with a white blush when ripe.
|Red-Osier Dogwood berries and twigs|
|Silky Dogwood berries, leaves, and twigs|
I looked at the flower arrangement next. The flowers were in a flat-topped white cluster. Both Silky and Red-Osier Dogwood have flowers arranged this way. This eliminated Gray Dogwood as a possibility. Its flowers are arranged in a cone-shaped cluster.
I looked back at the leaves again. There were five paired veins on most of the leaves in the pictures (some had 4 veins, others had six). This did not help either. Both Silky Dogwood and Red Osier can have 4 to six paired veins on each leaf. One source that I looked at said that Red-Osier has more prominent veins than Silk Dogwood- this was not much help because I was looking at a single shrub.
I had based my initial identification on twig color. Some of the twigs were red, others were green. I knew that Red-Osier usually has deep red twigs. It did not look right for Red-Osier. Symonds also said that the twigs of Silky Dogwood are often bright red (or maroon or green). I was fairly confident that this was Silky Dogwood.
Then I noticed there was one definitive way to decide between the Silky and Red-Osier species - pith color. Red-Osier has white pith and Silky has brown pith. Did I happen to notice the pith color? Of course not, the pith is in the center of the twigs. I didn't think that I would need to look inside the stem to identify the species.
Back to the swamp!
I went back to the park and decided to collect several samples of twigs, not only from the unknown Dogwood but also from two plants that I knew the species. The first was a Silky Dogwood.
|Silky Dogwood twigs, leaves, and flower buds|
|Silky Dogwood - closeup of leaves and flower bud|
Next was a Red-Osier Dogwood.
|Red-Osier Dogwood - closeup of flowers and leaves|
I also grabbed a sample from the original plant and took all three back to the office for closer examination.
|Three samples - Silky (upper left), Red-Osier (bottom left), unknown (upper right)|
|Silky Dogwood - note brown pith in twig. Red-Osier (not shown) has white pith.|
What about the unknown sample?
|Twig from unknown Dogwood|
|Note the white pith|
It had a white pith! It was a Red-Osier Dogwood (Cornus sericea). I was certain up to this point that it was a Silky Dogwood. It did not look like a Red-Osier, but the pith gave the final verdict. I learned something new today.