24 August 2009

An Undeniably Showy Sedge

"Sedges have Edges." That's the saying that all budding botanists learn in their first college botany course to help them remember how to differentiate a sedge from a grass or a rush. This saying is referring to the fact that the culms, or stems, of most (but not all) sedge species are triangular in cross-section. While there are several better ways to distinguish between the monocot families, this is apparently the character that academics thought would be easiest to teach, as the others often require use of a handlens and some patience. For example... Grass (Poaceae) flowers are modified into glumes subtending lemmas and paleas, within which the pistil and stamens are located. Rush (Juncaceae) flowers are comprised of tepals (petals and sepals) surrounding the stamens and pistil, with the structure one expects of a typical flower. Sedge (Cyperaceae) flowers are modified into scales subtending pistils, stamens, or both, sometimes with a corolla modified into bristles. When the ovary of a sedge flower matures to fruit, it is called an achene. In Carex, the largest genus within the Cyperaceae, the flower and later the achene are surrounded by a papery sac, called a perigynium, which is thought to be a highly modified bract.

Bristlystalked Sedge (Carex leptalea)

Unfortunately, the general public doesn't see sedges as anything more than "grass." The perigynia are often brown or green and small, and most often go unnoticed by the untrained eye. The most conspicuous portion of the plant is often the long, narrow, grass-like leaves. Personally, I disagree with the general public, and think that most sedges are quite intriguing and beautiful, once you get to know them.

Northeastern Sedge (Carex cryptolepis)

Yellowfruit Sedge (Carex annectens v. xanthocarpa)

While some will argue that most sedges are not showy, there is one sedge in North America that truly stands out from the rest. Instead of having brown or green perigynia, Golden Sedge (Carex aurea) has round, fleshy, orange perigynia (when mature) that look like tiny pumpkins! It is unknown why the perigynia of this species have evolved to this form, but some speculate that this may assist the plant in being dispersed by birds.

Golden Sedge (Carex aurea)

Golden Sedge can be found growing in wet, alkaline soils throughout most of the continent, with the exception of the southeastern United States and extreme northern Canada.
Who could think that this unique little plant is not attractive?


Justin Thomas said...

I had the best time quizing myself on those sedges! More, please.

Scott said...

How did you do on your quiz?

Justin Thomas said...

Well, if sedges have edges, I got them all right.

Scott said...

I would expect nothing less from you.