Photo by Allison Weakley

This week there are two mystery plants at once! These two species will serve nicely for a consideration of what we call a genus.

The concept of the genus as a taxonomic category really came into play among botanists in the late 17th Century. Briefly, a genus was recognized (and still is) as a convenient way to group closely related species. The dictionary definition of this word suggests group or kind, generally involving the notion of close relationships among its constituent members. Considered from the other perspective of grouping, a number of different but related genera (the plural of genus) are placed in a family. For instance, there are several species of elderberry which all belong to the genus Sambucus. The elderberries are related to honeysuckles, which are placed in the genus Lonicera. Both genera Sambucus and Lonicera belong to the family named Caprifoliaceae.

The two mystery plants both belong to the genus Hypericum, which contains about 40 different species found in North America. Hypericum is one of the several genera placed in the Hypericaceae, or St. John’s Wort family. Various species of Hypericum may be stout and shrubby, or low and herbaceous with flowers bearing either four or five petals.

Nevertheless, these species share enough features, especially those involving the flower parts, that they are all considered reasonably close relatives. Some members of this genus have been highly prized for medicines, such as the alleged anti–depressant qualities made from extracts from St. John’s Wort (Hypericum perforatum), and other species are valued as ornamental plants. Still others are known as annoying weeds.

The big–flowered mystery plant, on the left in the photograph, is a shrub with bluish–green foliage, sometimes waist–high, with peeling bark, and native to high ground and cedar glades from GA and TN into PA and into the Midwest and TX. Its bright gold flower is really showy with 400–500 stamens forming a conspicuous crown.

This species is grown widely in cultivation and sometimes escapes into surrounding countryside. Its small–flowered cousin on the right is an herb, mostly at home in damp places. It is fairly common from Quebec to FL often in ditches or floodplain forests or even in floating mats of vegetation on quiet lakes. Its comparatively humble flower features tiny, copper–colored petals with only about a dozen stamens.

Answer to last week’s mystery plant

Swamp mallow, Hibiscus moscheutos

Dr. John Nelson is, 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