Wednesday, March 13, 2013

Plant Quiz Solved: American Highbush Cranberry (Viburnum opulus var. americanum)

Jackie (Woodswalker) does it again!  She has correctly identified this as the American highbush cranberry (Viburnum opulus var. americanum).  It is also known as the American cranberrybush and some taxonomists give it full species status as Viburnum trilobum.  There is an excruciatingly similar European and Asian species (V. opulus var. opulus) that is often planted ornamentally throughout the eastern United States.  The major differences lie in the glands on the leaf petiole.  Our native variety has smaller glands that have a convex (rounded) tip, while the European variety tends to have larger glands with a noticeable concave (sunken) tip.  The pubescence of a leaf can further help distinguish the two as well: the native variety's upper surface has scattered appressed hairs, while the introduced variety has completely glabrous (hairless) leaf surfaces.

Despite its common name this is not at all a true cranberry (Vaccinium spp.) but instead a viburnum; very similar to our native and common blackhaw (V. prunifolium) and maple-leaved (V. acerifolium) species.  It's such named for its clusters of red, mature, cranberry-like fruit (all other Ohio viburnum's fruit is blue-black at maturity).  This particular specimen was photographed growing in the shrubbier margins of a undisturbed fen complex on the Bruce peninsula, Ontario; a typical habitat to find this species thriving in.  Here in Ohio, it is listed as state-threatened and only occurs in the bogs and fens of northeastern Ohio.  However, you will come across the nigh on invasive European variety in cultivation and sometimes see it in our more southern fens and wetlands where it has started to gain an unfortunate foothold.

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Time for yet another plant quiz!  Take a careful look at the photograph below and see what you think before commenting with your best guess or answer.  This particular specimen is in full bloom and an indigenous species to Ohio.  As usual best of luck and thanks to all those who decide to play along!

American Highbush  Cranberry (Viburnum opulus var. americanum)

6 comments:

  1. Replies
    1. Good answer; it is indeed a Viburnum and quite similar in leaf shape to our native maple-leaved species but it does not have the outer ring of sterile (very Hydrangea-like) flowers; only the inner, fertile ones.

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  2. This sure looks like Highbush Cranberry (Viburnum opulus var. americanum, formerly called trilobum). But maybe you have other similar Viburnums down there in Ohio that I wouldn't recognize. But definitely Viburnum.

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    Replies
    1. I had a hunch your northern knowledge would pay off on this one :)

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  3. My guess is Hydrangea quercifolia

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    1. That is a great guess but unfortunately that species is not native to Ohio and largely restricted to the southern Gulf states. The leaf shape and the outer ring of sterile flowers (very Hydrangea-like) could have easily pointed to the oak-leaved hydrangea.

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