Myriophyllum heterophyllum

Two Leaf Milfoil

Two Leaf Milfoil
Photo Courtesy USDA Plants Database

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Name:

• Myriophyllum, from the Greek, murios (myrios), "countless, infinite", and fullon (phyllon), "leaf; foliage"; hence "many leaved"
• heterophyllum, from the Greek, `eteros (heteros), "different, another kind", and fullon (phyllon), "leaf; foliage"; hence "differently leaved"
• Common name from its two distinctly different leaf forms
• Other common names include: Changeleaf Parrotfeather, Coontail, Coontail Moss, Two Leaf Water Milfoil, Variable-leaved Water Milfoil, Water Milfoil. Sold as Red Foxtail in the aquarium trade.

Taxonomy:

• 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: 27044

Description:

• A rooted perennial aquatic herb with a long, robust stem, usually deep red or brownish red in color.
• Leaves may exhibit two distinctly different forms.
  • Submerged Leaves fine and numerously dissected, in whorls of 4-6 or some scattered, ½"-2½" long, with 6-12 pairs of segments, yielding a delicate, feather-like or "coontail" appearance. This portion of the plant is usually a reddish or greenish brown in color.
  • Emergent Leaves small, bright green, and oval in shape, with or without teeth along the edges, up to ¼" wide, borne in whorls on a stalk-like portion of the stem, rising 6"-8" above the water. So different from the submerged leaves they are often mistaken as being another plant altogether. Emergent growth is generally associated with mature stages and may not be evident until late summer.
• Stem stout, simple or branching, 3mm-8mm in diameter, often tinged in red; to 3' or longer. Rather stout, smooth, branched. Winter buds produced at the plant base or from rhizomes.
• Roots white, unbranched, and thread-like. Not always present.
• Flowers in green to reddish spikes raised above the water's surface, 2"-12" long; the male usually in the upper part of the spike, the female in the lower. Floral bracts whorled, smaller than foliage leaves, ovate, sharply toothed, spreading, or curved downward; up to 1/24" long. Flowers both perfect and imperfect; petals of male and perfect flowers 1mm-3mm long.
  • Sepals 0
  • Petals 4 (at least in the male flowers), free from each other, up to 1/6" long, usually absent in the female flowers.
  • Stamens 4
  • Ovary superior (within blossom), 4-lobed, smooth.
• Fruit olive, more or less round, 2mm long; fruit segments rounded or with 2 small ridges or keels on the dorsal side, otherwise smooth. Conspicuously beaked with the recurved stigma.
• Seed

Identification:

• A rooted perennial aquatic herb, identifiable as a milfoil by its finely dissected, thread-like leaves.
• Distinguished from other native milfoils by:
  • its growth habit as our only milfoil generally rooted to the bottom
  • its smooth, stout, reddish stems
  • its two distinctive leaf forms, when visible on the same plant

Distribution:

• Quebec and Maine to South Dakota, south to Florida, Texas, and New Mexico.
• In Minnesota, known only from St. Louis County (last collected 1992)

Habitat:

• Lakes, ponds, pools in streams
• Thrives in clear, acidic waters; sometimes where calcium-rich.
• May be rooted in depths to 10'.

Associates:

• Birds: The fruits are eaten by waterfowl.

History:

Uses:

Reproduction:

• Sexually by seed (uncommon)
  • Flowers June-September
• Assexually by budding (most common)

Propagation:

• By rhizome division

Cultivation:

• 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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