Myriophyllum tenellum

Slender Water Milfoil

Slender Water Milfoil
Photo courtesy Wisconsin State Herbarium and Robert W. Freckmann

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The natural history of the northwoods

Name:

• Myriophyllum, from the Greek, murios (myrios), "countless, infinite", and fullon (phyllon), "leaf; foliage"; hence "many leaved"
• tenellum, from the Latin, tenellus, "tender"
• Common name from the slender, leafless stems - such a contrast with the other other, leafy milfoils.
• Other common names include: Leafless Water Milfoil

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: 503907

Description:

• Leaves absent, or reduced to the occasional scale
• Stem slender, upright, and largely unbranched; 4"-12"
• Roots white, unbranched, and thread-like. Not always present.
• Flowers on ¾"-2" spikes raised above the water's surface; floral bracts mostly alternate, oblong to obovate in form, similar in size to the flowers.
• Sepals
• Petals
• Stamens
• Pistil of 4 chambers
• Ovary superior (within blossom)
• Fruit nut-like, 4-lobed with one seed per lobe; segments rounded on back and at base, 1mm long

Identification:

• A submerged, leafless aquatic plant
• Distinguished from other native milfoils by the lack of leaves, so prominent in the other species.

Distribution:

• Newfoundland and Quebec to Minnesota, south to New Jersey.

Habitat:

• Acid lakes, often forming large colonies in deep water.

Associates:

History:

Uses:

Reproduction:

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

Propagation:

• By 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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