This species is the smallest Lemna. It is widespread from South to western North America, but concentrated in relatively dry warm temperate regions, becoming infrequent to rare east of the Mississippi Rv. (K; Crawford et al. 1996). The species may have spread north since settlement; records north of the southeastern Coastal Plain mostly date from after 1950 (SERNEC). After 1960, it has become a problematic invasive species across much of Europe (Ceschin et al. 2020). L. minuta is easily confused with minor, and has probably been often overlooked. As well as general reports from Ky. (FNA 22, J, W), the species has been recently discovered on travertine seeps along Boone Creek in FAYE (JC), at Cove Spring Park in FRAN (JC) and at Jessamine Gorge in JESS (JC). It is allied with valdiviana; see notes under that name. Compared to minor, minuta has only one nerve and this is often obscure (versus 3-5), roots are usually shorter (up to 1.5 cm versus 15 cm), and maximum frond size is usually smaller (up to 4 mm long versus 8 mm); 2n = 36, 40, 42. L. minuta has been found to outgrow minor at high phosphate levels but not at low levels; both species respond greatly to high nitrate or ammonium levels (Paolucci et al. 2016). Flowering has not yet been reported in Ky. or in most other eastern states.