Myriophyllum alterniflorum

Alternate Flowered Milfoil

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The natural history of the northwoods


  • Myriophyllum, from the Greek, murios (myrios), "countless, infinite", and fullon (phyllon), "leaf; foliage"; hence "many leaved"
  • alterniflorum, from the Latin, alternus, "by turns, alternate"; and florus, "flower"; hence "alternating flowers"
  • Common name from the arrangement of the barren flowers on the floral spike
  • Other common names include: Slender Water Milfoil, Alternate Water Milfoil (UK), Hår-Tusindblad (Dan), Rusko-ärviä (Fin), Snàthainn Bhàthaidh (Gaelic), Wechselblättriges Tausendblatt (Ger), Sikjamari (Is), Tusenblad (Nor), Hårslinga (Swe)


  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Magnoliopsida, the Dicotyledons
      • Subclass Rosidae
        • Order Haloragales
          • Family Haloragaceae, the Water Milfoils
            • Genus Myriophyllum, the Water Milfoils
  • Taxonomic Serial Number: 503903
  • Also known as Myriophyllum alterniflorum var. americanum


  • A perennial aquatic herb
  • Leaves in whorls of 3-5, usually less than 3/8" long; shorter than the stem internodes, pinnately divided.
  • Stem very slender
  • Roots white, unbranched, and thread-like. Not always present.
  • Flowers on a short leafless spike, ¾"-2" long, raised above the water's surface. Bracts mostly alternate, linear, shorter than the flowers; barren flowers alternately arranged in a short leafless spike, with the fertile flowers about three together, in the axils of the leaves, at its base.
    • Petals 4, pink, on male flowers
    • Stamens 8
    • Pistil of 4 chambers
    • Ovary superior (within blossom)
  • Fruit nut-like, 4-lobed with one seed per lobe; segments 1mm-2mm long, rounded on back and base.


  • A submerged aquatic plant, identifiable as a milfoil by its finely dissected, thread-like leaves.
  • Distinguished from other native milfoils by
    • short leaves, typically less than 3/8" long
    • leaves shorter than stem internodes
    • alternate arrangement of flowers (when present)


  • Greenland to Newfoundland, Ontario, and Minnesota; south to Massachusetts and New York.


  • Acidic lakes. Also Lake Superior shore.





  • Sexually by seed (uncommon)
  • Assexually by budding (most common)


  • By division


  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Useful as oxygenator in garden ponds, and as shelter for small fishes and aquatic invertebrates.



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Last updated on 26 February, 2004