Saturday, May 12, 2012

Spring Flowers: Cancerroot

Orobanche uniflora (Cancerroot, Naked Broomrape, ) is a member of the plant world's misfit group:  the plants that don't photosynthesize.  These are the plants that cause you to say, "wait, I learned in elementary school that the definition of a plant is that it makes its own food."  Which is true.  Except when it isn't.  This group of plants includes parasites (feeds on living things) and saprophytes (feeds on decaying matter).  Many plant families included species that are parasitic or saprophytic. O. uniflora is a member of the Broomrape Family (Orobanchaceae), of which all of the species are at least partially parasitic. The fully parasitic plants (holoparasites) are pale white or cream colored, since they lack chlorophyll, and their leaves are reduced to stubby scales. Orobanchaceae also includes some plants that are hemiparasitic, meaning they both photosynthesize and feed on other living plants (I guess they have their bases covered).

O. uniflora is a holoparasite that is found throughout North America.  In the Mid-Atlantic it blooms in late spring.  The flowers are usually 3-5 inches tall and pale white to very pale lavender.  Common host plants include Solidago spp. (Goldenrods),  Saxifraga spp. (Saxifrages), and Helianthus spp. (Sunflowers).  The flowers are pollinated by insects or can self-pollinate.

I profiled another parasite last year, Monotropa uniflora (Indian Pipe), which is a member of the Heath Family (Ericaceae).

 Orobanche uniflora on the Weakley Hollow Fire Road in April of this year.  (Shenandoah National Park).
A group of O. uniflora on the Old Rag Ridge Trail in May 2011 (Shenandoah National Park).
Another example from the Tuscarora Trail in Cowans Gap State Park, Pennsylvania.

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