The Original Mystery Plant
Dr. John Nelson

Photo by John Nelson

In the South, we often hear about thatch, which is an unhappy lawn situation involving a dense layer of decayed vegetation, inconveniently wedged between the ground and the roots of centipede grass.

The Mystery Plant is well known as the best source of roofing thatch there is. Thatched roofs are no longer common, although they were a fairly regular sight in many parts of Europe well into the 20th century. It takes a very sharp blade to cut this, and its harvesting is quite labor- intensive.

The Mystery Plant is a handsome grass- a tall one, capable of reaching 12- feet in height and shown here in a marsh at Georgetown, S.C. Some botanists maintain there are three or four different species involved, but these integrade so much that it may be more convenient to consider all the plants a single species.

It grows from stout rhizomes, and spreads readily. The stems or culms are hollow. In flower, a purplish panicle is produced at the very top of the culm. A tiny feather- duster of soft hairs is produced at the base of each grain, and these help the grains float around on the surface of the water.

By and large, it is the rhizomes that spread the plants. However, seed production is usually rare. The species is one of the most widely distributed plants in the whole world, and it also grows in places that freeze in the winter. It is a plant of wet places most often seen in estuaries and marshes.

Some plant geneticists are convinced that various European strains of this species, slightly different from the native American versions, have invaded our shores. This has led to remarkably vigorous infestations in many places. In fact, this species is regarded as one of the worst weeds in many parts of New England and as far south as New Jersey. It's one of the major components of the meadowlands along I- 95.

This species can be found moving into places along the coast of the Carolinas and Georgia and is becoming a serious pest, capable of producing dense stands in sites that previously offered habitat for waterfowl. Huge numbers of the plants in one place are likely to change aspects of the local soil chemistry as well as hydrology. There are plenty of questions remaining on the biology and control of this species. Fire won't kill it and digging it out frequently results in spreading the rhizomes. Answer to this week's mystery plant [Answer: "Common reed," Phragmites australis]

Dr. John Nelson is the curator of the USC Herbarium. To learn more about the Herbarium, call 777-8196. The

department also offers free plant identification.

www.herbarium.org