Small-flowered lipocarpha (Lipocarpha micrantha) COSEWIC assessment and status report: chapter 3

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SPECIES INFORMATION

Name and classification

Recent treatments of this species, including the upcoming Flora of North America publication (Tucker, in press) refer it to Lipocarpha micrantha (Vahl) G. Tucker, as proposed by Tucker (1987).  Older synonyms include Hemicarpha micrantha (Vahl) Pax, Hemicarpha micrantha (Vahl) Britton, Hemicarpha micrantha var. minor (Schrad.) Frieland, Hemicarpha micrantha (Vahl) Pax var. micrantha, and Scirpus micranthus Vahl.  No other species or subspecies of Lipocarpha or Hemicarpha occur in Canada. 

Lipocarpha micrantha is a sedge, in the family Cyperaceae.  Sedges are rarely referred to with a vernacular name.  However, in addition to Small-Flowered Lipocarpha, this species has been called Dwarf Bulrush (NatureServe 2001), and the generic names Lipocarpha and Hemicarpha are also sometimes used as common names. According to Kartesz (1999), the genus Lipocarpha comprises the “Halfchaff Sedges”.

Description

Lipocarpha micrantha is a very small annual plant (figure 1).  At flowering the stems and leaves are often less than 10cm tall, and are about 0.5mm wide.  The flowers are arranged in dense oval spikes 2-6mm long.  There are 1-3 spikes on each stem, which are subtended by 1-3 leafy bracts.  Each spike has numerous inconspicuous flowers.  The reproductive structures are concealed by mucronate scales 1-2mm long (Gleason and Cronquist 1991).

The densely tufted plants resemble the seedlings of many other sedge species that occur in the same habitat.  In Canada Lipocarpha micrantha is perhaps most similar in aspect to Cyperus squarrosus, another small annual sedge.  Lipocarpha micrantha is distinguished from this and all other Cyperus species by the shape of the flower head.  Cyperus flowers are borne in two-sided spikes, whereas Lipocarpha flowers are arranged in a dense cone shaped head. These flower heads are less than 5mm long, so careful inspection is required to verify the identity of the plant.

Full technical descriptions of Lipocarpha micrantha can be found in various regional manuals (Gleason & Cronquist, 1991, Fernald 1950, etc.) as well as in the upcoming Flora of North America publication (Tucker, in press).