Study plants for any length of time and one will eventually hear the phrase “sedges have edges”. This is because the stems of sedges typically have three angles, distinguishing them from the terete (round in cross-section) stems of grasses. For quite some time that was about the extent of my knowledge of this group of plants. A few years ago I decided to get serious about learning sedges, particularly the species rich genus Carex. One characteristic of plants in this genus is that the achene (seed) is surrounded by a sac known as a perigynium (plural perigynia). Close examination of these structures and the scales subtending them is often key to proper identification of plants in this genus. The perigynia are relatively large and inflated in Shining Bur Sedge (Carex intumescens), shown below.
Recently I have been adding photographs and descriptions for Carex species to my Plants of the Northeastern U.S. website. One goal has been to document important details of the inflorescence using a dissecting scope including a ruler marked in millimeters. Recently added pages include those for Carex brunnescens, C. debilis, C. deweyana, C. disperma, C. hystericina, C. interior, and C. radiata.