Sunday, July 22, 2012

Rosepink (Sabatia angularis) Revisited


July 7th – July 14th, 2012. Rosepinks (Sabatia angularis) are one of my favorite wildflowers. With the drought, I’d almost given up hope of seeing them in bloom this year. But then we saw them in the Wilson Shoals WMA (Banks County, Georgia) and, last weekend, in Hancock County, Georgia, where we saw them last year.

I wanted to learn more about this plant since it was obvious that the style was not fully extended when the flower first opened but became erect over a number of days to expose the stigma for fertilization. Marvin at Nature in the Ozarks demystified the process.

Sabatia angularis is unusual in being protandrous, meaning that the anthers release their pollen before the stigma of the same flower is receptive to fertilization. This minimizes self-fertiliation and promotes cross-fertilization to maximize genetic diversity in the species. There is a good description of this process here.


The plants we found were blooming profusely


When the flowers open the style, which is bifurcated but twisted closed to prevent access of pollen to the stigma, lies back against the petals with the branches of the stigma folded until the flowers supply of pollen is depleted.


 The style then stiffens, lifting it off the petals.

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The bifurcated section begins to unwind, until the...


style with stigma stand erect above the petals. The stigma is then accessible to pollen from other flowers.

Sabatia angularis is known by the common names Rosepink Rose-pink, Bitter-bloom, Common Marsh-pink, and Square-stem Rose Gentian. Plants are biennials. They are native to the United States where they occur in the Eastern United States (excepting the New England states) to Florida and west to Kansas, Oklahoma, Texas and New Mexico. In Georgia, they occur mainly in counties in the Piedmont. We saw these first in Gilmer and Pickens counties in North Georgia in July, 2010; last year, we saw them in Taliaferro, Hancock, and Jasper counties.
Click on an image to view a larger image

Identification resources: 
- Southeastern Flora: Rosepink (Sabatia angularis)
- Natural and Naturalized Plants of the Carolinas and Georgia: Sabatia angularis (Rose-pink, Bitter-bloom, Common Marsh-pink)
- Missouri Plants: Sabatia angularis
- Kansas Wildflowers and Grasses: Sabatia angularis

Distribution:
- United States Department of Agriculture Plants Database: Sabatia angularis (Rosepink)
- University of North Carolina Herbarium: Sabatia angularis

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2 comments:

Hemlock said...

Wonderful photos and description! Found these today on the Bartram Trail, and enjoyed seeing your wonderful photos of how the style unfolds.

JSK said...

Glad you enjoyed them. It's fascinating how many different mechanisms plants develop to encourage or discourage diversity.