Lemna trisulca

Ivy Leaf Duckweed

Ivy Leaf Duckweed, Photo Courtesy USDA Plants Database
Ivy Leaf Duckweed
Photo Courtesy USDA Plants Database

Flora, fauna, earth, and sky...
The natural history of the northwoods


Name:

  • Lemna, from the Greek, lemna, a water-plant, star-grass, Callitriche verna
  • trisulca, from the Latin, trisulcus, "with three furrows, three-cleft, three-forked, trifid, triple"
  • Common Name, from the perceived similarity to an ivy leaf.
  • Other common names include: Star Duckweed, Ivy-leaved Duckweed (UK), Lenticule trisulquee (Qué), Kors-Andemad (Dan), Ristilimaska (Fin), Gràn Lachan (Gaelic), Dreifurchige Wasserlinse (Ger), Punktkroos (NL), Krossandmat (Nor), Zaburinka Trojbrázdová (Slovak), Korsandmat (Swe)

Taxonomy:

  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Liliopsida, the Monocotyledons
      • Subclass Arecidae, the Arum
        • Order Arales, the Arum
          • Family Lemnaceae, the Duckweeds As a result of their adaptation to aquatic habitats, they are among the smallest and simplest of the flowering plants, floating monocotyledons, only 1-15mm in size.
            • Genus Lemna, 13 species worldwide
  • Taxonomic Serial Number: 42595

Description:

  • A ¼, ½, ¾, º, é
  • A diminutive floating aquatic perennial, often forming tangled masses just under the water surface.
  • Leaves and Stems merged in common structure typically called a frond or thallus, though neither term is correct by strict botanical definition.
  • Frond oblong-lanceolate to elliptic and flat, tapering at base to long, slender stalk (stipe). Each frond typically ¼"-¾" long with three veins, the middle vein most prominent. Two budding pouches are locaed on either side of the basal end. Multiple fronds are joined by long, attenuated stalks to form star shaped floating colonies at, or just below, the surface of the water.
  • Roots often absent or a single root.
  • Flower of two stamens and a single pistel in a membranous cuplike spathe, hidden away inside the budding pouches. Flowers uncommon, occuring in somewhat smaller fronds with toothed margins.
  • Because Duckweed is largely made up of metabolically active cells with very little structural fiber, the tissue contains twice the protein, fat, nitrogen, and phosphorus of other vascular plants. Each frond absorbs nutrients through the whole plant and not through a central root system, directly assimilating organic molecules such as simple carbohydrates and various amino acids. With the entire body of the duckweed composed of non-structural, metabolically active tissue, most photosynthesis is devoted to the production of protein and nucleic acids, making them very high in nutrional value.
  • Roots to 2.5 cm (sometimes not developed), tip pointed; sheath not winged. Green stalks 2--20 mm. Fronds submersed (except when flowering or fruiting), 3--50, coherent and very often forming branched chains, narrowly ovate, flat, thin, 3--15 mm (excluding stalk), 2--3.5 times as long as wide, base suddenly narrowed into green stalk, margins denticulate distally; veins (1 or) 3, lateral veins only in proximal part of frond; papillae absent; anthocyanin often present; air spaces shorter than 0.3 mm; turions absent. Flowers: ovaries 1-ovulate, utricular scale with narrow opening at apex. Fruits 0.6--0.9 mm, laterally winged toward apex. Seeds with 12--18 distinct ribs, staying within fruit wall after ripening. 2n = 40, 42, 44, 60, 63, 80.

Identification:

  • Identifiable as a Duckweed by its diminutive size and free-floating habit.
  • Distinguished from the other two North Country duckweeds, Greater Duckweed (Spirodela polyrhiza) and Lesser Duckweed (Lemna minor) by its elongated frond with prominent stalk (the others have much rounder fronds, without a stalk).
  • The chains and clusters formed are unique among North American duckweeds.
  • The smaller, and much less common, flowering fronds can readily be separated from other Duckweeds by their toothed margins.

Distribution:

  • Temperate zones throughout the northern hemisphere (Asia, Europe, and North America), as well as Africa and Australia.

Habitat:

  • Shallow waters of marshes; edges of ponds, lakes, and streams; and moist soils, sometimes extending into mountain meadows at higher elevations.
  • Flowering (rare) late spring--summer. Mesotrophic, quiet waters rich in calcium, in cool-temperate regions; 0--3000 m; Alta., B.C., Man., N.B., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; nearly worldwide, except arctic and antarctic regions and South America; in warm regions only in mountains.

Associates:

  • Natural populations of duckweeds are usually mixtures of several species.
  • Trees: Tammarack (Larix laricina), Black Spruce (Picea mariana)
  • Shrubs: Bog Birch (Betula pumila), Leatherleaf (Chamaedaphne calyculata), Sweet Gale (Myrica gale)
  • Herbs: Blue Flag Iris (Iris versicolor), Cattails (Typha spp)
  • Ground Covers: Sphagnum Mosses (Sphagnum spp.)
  • Mammals: Moose (Alces alces)
  • Birds: Great Blue Heron (Ardea herodias)

History:

Uses:

  • Very important in the ecosystem as an essential link in the food chain.
  • Duckweeds are useful as a water crop as they can acclimatize themselves to almost all growing conditions, with some thriving in manure-rich or eutrophic waters. They reproduce quickly, extending over large surface areas, and are easily harvested. Their high fat and protein content makes them a source of food for animals and poultry.
  • Duckweeds have potential in wastewater treatment, absorbing excess nutrients from surface waters, including phosphorus and ammonias, reducing suspended solids, and reducing biochemical oxygen demand.

Reproduction:

  • Reproduces by seed and vegetatively, thought during the growing season, nearly all plants arise by vegetative reproduction.
  • Unlike the ordinary leaves of most plants, each duckweed frond contains buds from which more fronds may grow. These buds are hidden in pouches along the center axis of older fronds. As they grow, new fronds emerge through slits in the side of their parent fronds. Until they mature, daughter fronds may remain attached to the parent frond. Rapidly growing plants often have three or four attached fronds, giving rise to this plant's common names.
  • Flowers are uncommon but, where present, the flowering plant fronds tend to be shorter and thicker than the typical non-flowering frond, with toothed margin and shorter stalk. They float at water surface like most other Duckweed species.
  • Plants may overwinter as seeds or as adult plants submerged beneath the ice. This species is not known to produce the overwintering turions, dormant vegetative structures, found in other Duckweeds.
  • Duckweed reproduce at twice the rate of other vascular plants.

Propagation:

  • By benign neglect

Cultivation:

  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Easily grown in garden ponds, where it removes excess nutrients from the water while providing surface shade, both of which act to inhibit algae growth.
  • Like most water plants, does best in full sun.
  • Goldfish, and other carp, are particularly fond of duckweed. Keep a "starter batch" in a separate, fish free container or pond, if the fish are too voracious.
  • Can be invasive in garden ponds without goldfish, but can be controlled rather easily by surface skimming with a hand skimmer from a swimming pool supplier. Just throw it in the compost - it's rich in nutrients.

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Last updated on 26 February, 2004