Part 58 Juncaceae-Lemnaceae
Juncaceae are represented on the islands by two genera, Juncus with seven naturalized species and Luzula with one endemic species. Juncus, the common bog rush, enjoys a cosmopolitan distribution with its 300 plus species occurring in wet and marshy habitats. The Hawaiian species fit into this general description occurring as stream-side plants on most of the islands with the exception of Ni`ihau and Kaho`olawe, both of which lack sites that are wet enough. Juncus effusus (see image), commonly known as the Japanese mat rush, is known from Maui, Moloka`i, and the Big Island.
Luzula hawaiiensis (see image) occurs in a variety of habitats on all of the main islands except Ni`ihau and Kaho`olawe.
Lemnaceae, the duckweed family, consist of six genera and about 30 species; all are aquatic. The Hawaiian Islands have representatives of three genera: Lemna, Spirodella, and Wolffia with two, two, and one species, respectively. The most common duckweed is Lemna perpusilla, which occurs on all of the main islands, with the exception of Ni`ihau and Kaho`olawe. It can be found in almost any kind of standing water, including taro patches as shown in the illustration (see image). It is not known with certainty if this is a naturalized or indigenous species; it, and the other species, could easily have been brought to the islands on the feet of migrating water birds. Lemna perpusilla (see image) was photographed at a small taro farm on the southern coast of Moloka`i, where it was growing with the water fern Azolla filiculoides. Lemna is the green plant, Azolla the pigmented one. The author's index finger is included for scale.
Genera historically considered part of Lemnaceae, now submerged into Araceae, are lumped together as the subfamily Lemnoideae.
January 15, 2013