Observations of the Month: Schoenoplectus (Cyperaceae)

Common Tule (S. acutus var. occidentalis) https://www.inaturalist.org/observations/17108781

California Bulrush (S. californicus) https://www.inaturalist.org/observations/17108812
Common Three-square Bulrush (S. pungens var. longispicatus) https://www.inaturalist.org/observations/13690606
American Three-square Bulrush (S. americanus) https://www.inaturalist.org/observations/12746716

Perhaps like me, you learned the simplistic rhyme “sedges have edges, rushes are round, grasses are hollow from tip to the ground” to help you remember how to distinguish the families of plants often found in marshy or wet areas—sedges (Cyperaceae), rushes (Juncaceae), and grasses (Poaceae). If you are examining sedges in the genus Schoenoplectus, an exception to the rhyme may become apparent, but the exception will help you sort out the species. There are four species in this genus found in San Diego county. Two of these, Schoenoplectus acutus var. occidentalis and S. californicus, have panicle-like inflorescences near the tip of the stem and at first, they appear very similar. But on closer inspection, S. acutus var occidentalis is the exception to the rhyme: although it is a sedge, the stem is rounded, not 3-angled. The stem of S. californicus has edges, but they are not sharp edges. The two other species, S. pungens var. longispicatus and S. americanus, have the expected sharply-edged stems with head-like inflorescences on the side of the stem. As longispicatus (the scientific name of the variety found in San Diego) suggests, the stem-like bract above the inflorescence is longer on S. pungens var. longispicatus compared to S. americanus which has a shorter stem-like bract beyond the inflorescence. S. pungens var. longispicatus also has longer basal leaves than S. americanus which has short basal leaves. You can see the similarities and differences of these four species in the observations of the month, posted by Dr. Jon Rebman and Matthew Salkiewicz. When you are photographing one of these plants for an observation, be sure to photograph the stem (to show its shape), the inflorescence (to show its character), the basal leaves (to show their length), and the plant as a whole. This will help others verify which species of Schoenoplectus you have found.

Posted on October 31, 2018 11:28 PM by milliebasden