The Lemnaceae family consists of five genera (Spirodela, Landoltia, Lemna, Wolffia and Wolffiella), and currently comprises a total of 35 recognized species (see below, following ISCDRA).
Lemnaceae or Lemnoideae: family or sub-family?
Although on this site we generally refer to duckweeds as "the family" Lemnaceae, there is some controversy on whether duckweeds are a family or rather a sub-family of the Araceae. Duckweeds were first defined as a family by Martinov in 1820. In 1876, Engler was the first to classify them as a sub-family within the Araceae, but by 1889, he reconsidered and treated them again as a separate family. For much of the following period, duckweed researchers regarded duckweeds as a sister group to the Araceae family. In 2009, the Angiosperm Phylogeny Group (APG) III reclassified duckweeds as part of the Araceae family, placing them as a subfamily, Lemnoideae, within Araceae rather than as a separate sister taxon. This classification was upheld by APG IV. More recently, several duckweed researchers have contested this classification, arguing that the family Lemnaceae satisfies the taxonomic criteria to be recognized as a distinct family (see Tippery et al., 2021). To accommodate this, Tippery et al. proposed to separate Araceae into three separate families: Araceae, Lemnaceae, and Orontiaceae, a separation supported by both morphological and phylogenetic evidence.
