Shrubs Of The Great Basin: A Natural History

Dwarf Ninebark

Dwarf Ninebark Physocarpus altemans THE WESTERN DWARF NINEBARK, like its eastern counterpart, is easily recognized by its bark-which tends to peel off in narrow strips, exposing the lighter bark beneath. Within the Great Basin it is most easily confused with the wax currant, which has leaves of similar size and shape. However, the latter does not have bark which peels in the fashion of ninebark, and, of course, the fruits of the wax currant are easily distinguished from the dry capsules of the ninebark. Also, the young branches and leaves of the nine, bark are pubescent, with star'shaped or stellate hairs seen under a hand lens, totally unlike the simple pubescence on the wax currant. Dwarf ninebark is a low shrub ranging from 25 centimeters to a little over 1 meter high in favorable locations. The rounded leaves vary from 6 to 20 millimeters long. Frequently, they are three,lobed. The clusters of three to six white flowers are borne at the ends of the smaller branchlets. The petals, only 4 to 5 millimeters long, are borne at the edge of a small cup, in a fash, ion that is similar to those of many other members of the rose family. The fruit which develops from the single pod is an inflated capsule about 5 milli, meters long. The genus name Physocarpus comes from the Greek physa, meaning bellows, and karpos, meaning fruit. The pods or capsules are hygroscopic-splitting open at the tip during dry weather to release the seeds but closing during wet weather. This kind of response is common in many plants, all the way from mosses to higher plants. Dispersal of seeds or spores during dry weather generally means that they will travel farther and thus be more likely to colonize areas with similar habitats, and this confers an obvious evolutionary advantage on such a population. The species name altemans is in reference to the twenty or so stamens, some of which are longer with supporting stalks or "filaments" somewhat wider at the base. 166 DWARF NINEBARK The common name of ninebark is assumed to have originated from the numerous layers of bark which successively peel from the shrub's stems, al~ though one authority believes that it originated from the number of medici~ nal uses for which the plant was noted. However, the western ninebark seems to have been little used-the Indian Medicine Project of the U.S. Department of Agriculture during the 1930S turned up no evidence that it was employed by Great Basin tribes, probably because it is not a common plant anywhere in the area. The western ninebark inhabits dry, rocky slopes within and above the pinyon~juniper zone to an elevation of 10,000 feet. Altogether there are about fourteen species of ninebark, thirteen of these in North America and one in eastern Asia, according to many manuals. However, John and Rose~ marie Kartesz, in a recent book, A Synonymized Checklist ofthe Vascular Flora of the United States, Canada, and Greenland, reduce this number to five, since only minor differences separate most of the so~called species. To the ama~ teur, this kind of situation makes it appear that botanists are pretty conten~ tious or at least that they have trouble getting their act together! Actually, it indicates that the concept ofa species is a human invention-and not neces~ sarily one that fits the natural situation in all instances. We like to pigeonhole things in order to think about them more easily, but more often than not in nature a continuum is the case. It should not be inferred from these remarks that the concept of a species is not a worthwhile artifice, for without it we would be at a loss to understand nature, but it is essential to remember that it is an abstract notion, very much like our notion of the electron! The one species of ninebark which occurs in eastern Asia is an example of a disjunct distribution and an indication that, before the last series of glaciations, the ninebarks were more numerous and more widely distributed over the world. This is yet another example of the close affinity between the eastern temperate Asian flora and the flora ofeastern North America. Tulip trees, magnolias, witch hazels, and a number of other genera show a similar disjunct distribution between eastern North America and eastern Asia. ...