The original mystery plant
Each week The Columbia Star features an explanation and picture of a
mystery plant given by Dr. John Nelson, the curator of the USC Herbarium. To learn more about the Herbarium, call him at 777-8196. His department also offers free plant identification. www.herbarium.org
This time we have a spectacular fall bloomer, which you will see commonly on roadsides, in vacant lots, and at the margins of agricultural fields. It is, of course, a member of the bean family, or fabaceae. It features a large, colorful flower that is very useful in my plant taxonomy class. The parts are easy to dissect and count.
There are five greenish sepals, united at their bases. The flamboyant corolla consists of five bright yellow petals. The upper petal is called the banner or standard (or vexillum if you really want to get fancy). If you look closely, you will see this upper petal is finely striped in the lower portions. Two other yellow petals are called wings along the sides. At the bottom of the flower are two small, paired petals, called keels, and these envelope and protect the ten stamens and single pistil.
This is a beautiful plant. It is an annual in our area but may behave as a perennial in the tropics. It is native to India and other parts of southern Asia. It is presently widespread throughout the Southeast, occurring from NC to Texas, and then up the Mississippi River valley to Illinois and Missouri. It is also a serious pest now in Hawaii.
How did it get to the Southeast? This species, being a member of the bean family, was recognized early as a way of improving soil through its natural propensity for nitrogen fixation. Nitrogen from the air can be incorporated into the soil with the aid of friendly bacteria hiding amongst the roots, and thus the soil is improved for growing crops.
After the flowers are finished, bright green bean pods are produced, each containing up to 20 or so small seeds. When the pods are dry and black, the seeds rattle around easily in their confined space. The scientific name of the plant, in a clever way, refers to a rattlesnake’s rattles, and the scientific genus name for the rattlesnake is crotalus.
The problem is that the seeds are somewhat poisonous. In fact, they may be dangerously poisonous to poultry and other wildlife. Once again, a sort of good news/bad news plant introduction.
Answer to last week’s mystery plant