Lemna is the ancient Greek name for this water plant given by Theophrastus, the "Father of Botany". The species name means very small (Fernald 1950) and is a good name for a plant no bigger than the point of a pencil.
There are three existing populations but there is no detailed information on their size and quality. The plant was recorded in 18 different locations between the late 1800s and the mid-1940s and most of them still need to be rechecked. Five populations no longer exist because their habitat has been destroyed.
There are no recent surveys to determine short-term trends.
This aquatic plant seems to be in decline since there were 18 known populations in the past but now only three are known. Many of the ponds where it occurred are now developed or have been altered from the original natural state.
Specific threats are unknown at this time but many of the ponds on Long Island are subject to shoreline development, pollution and herbicide treatments.
Management needs are unknown at this time.
More collection needs to be done of these small aquatic plants on Long Island to determine the relative abundance of each species.
These aquatic plants can be found in kettlehole ponds, the surface of rivers, in ponds, springs, rivers and lakes, particularly quiet waters (New York Natural Heritage Program 2012).
There are historical records scattered throughout the lower Hudson counties and on Long Island. Populations presently exist on Staten Island and on Long Island.
This aquatic plant occurs along the Atlantic coastal states from Vermont south to South Carolina and along the Gulf Coast from Georgia to Louisiana and eastern Texas. It is less common in the upper Midwest and South Central states but becomes more common as it reaches its western limits in Nebraska and Kansas.
This tiny aquatic plant has a thallus that is convex on both sides, with a prominent papilla at the node and apex above, and usually with smaller papillae along the midline. They have obliquely obovate leaves with rounded sides, 1-2.5 mm long, commonly 1-2 times as long as wide. The leaves are not anthocyanic. The root tip is pointed and the seeds orthotropous.
Distinguishing characteristics: thallus convex on both sides, with a prominent papilla at node and apex above, and usually with smaller papillae along the midline, obliquely obovate with rounded sides, 1-2.5 mm, commonly 1-2 times as long as wide, not anthocyanic; root tip pointed; seeds orthotropous. Best life stage for ID: in fruit or flower. Characteristics needed to ID: vegetative plants, fruit or flowers helpful.
The best time to identify this plant is when it is in leaf.
Lemna valdiviana has a more oblong thallus with nearly parallel sides, 2.5-5 mm long, commonly 1.5-3 times as long as wide. Lemna minor has a rounded root tip with amphitropous seeds, thallus symmetrical, flat.
It can be identified vegetatively June through October. It reproduces during September and October.
The time of year you would expect to find Minute Duckweed vegetative in New York.
Lemna perpusilla Torr.
Flora of North America Editorial Committee. 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.
Bookout, Henry. 1996. Sexual reproduction in Lemna Perpusilla Torr. Long Island Botanical Society Newsletter 6(1):1. January - February 1996.
Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.
Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.
Hellquist, C.B. and G.E. Crow 1982. Aquatic vascular plants of New England: part 5. Araceae, Lemnaceae, Xyridaceae, Eriocaulaceae, and Pontederiaceae. New Hampshire Agricultural Experiment Station, University of New Hampshire. Station Bull. 523.
Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.
House, Homer D. 1924. Annotated list of the ferns and flowering plants of New York State. New York State Museum Bulletin 254:1-758.
New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.
New York Natural Heritage Program. 2019. New York Natural Heritage Program Databases. Albany, NY.
Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.
Seymour, F.C. 1982. The flora of New England. A manual for the identification of all vascular plants including ferns and fern allies growing without cultivation in New England. Moldenka, Plainfield, New Jersey.
Taylor, Norman. 1915. Flora of the vicinity of New York. Memoirs of the New York Botanical Garden vol. V. New York, NY.
Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York
This guide was authored by: Stephen M. Young
Information for this guide was last updated on: April 18, 2019
Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Lemna perpusilla. Available from: https://guides.nynhp.org/minute-duckweed/. Accessed July 18, 2019.