Eriocaulon aquaticum


Pipewort, Eriocaulon aquaticum, Photo courtesy Wisconsin State Herbarium and Andrew Meeks
Photo courtesy Wisconsin State Herbarium and Andrew Meeks

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The natural history of the northwoods


  • Eriocaulon, from the Greek, 'erion (erion), "wool", and kaulos (kaulos), "plant stem"; hence "wooly stem"
  • aquaticum, from the Latin, aquaticus, "living, growing, or found in or by the water; aquatic".
  • Pipewort, from its shape and the Anglo-Saxon wort, "plant"
  • Other common names include Button-rods, Hat-pins, Sevenangle Pipewort, Eriocaulon aquatique (Qué), Ṕoban Uisge (Gaelic)


  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Liliopsida, the Monocotyledons
      • Subclass Commelinidae
        • Order Eriocaulales, the Pipeworts
          • Family Eriocaulaceae, the Pipeworts
            • Genus Eriocaulon, the Pipeworts
  • Taxonomic Serial Number: 502404
  • Also known as Eriocaulon pellucidum, Eriocaulon septangulare, Cespa aquatica, Eriocaulon articulatum, Eriocaulon pellucidum, Eriocaulon pumilum, Nasmythia articulata, Nasmythia septangularis
  • The name Eriocaulon septangulare, widely used for this species, is not regarded as valid. Some would consider North American plants to be distinct from Eurasian ones, using the name Eriocaulon pellucidum.


  • A tiny lakeshore perennial of clear, shallow waters.
  • Leaves thin, grass-like, 1/2"-4", almost translucent; in basal rosette
  • Stem single, leaf-less, with slight twist and 5-7 ridges (which account for its former botanical species name of septangulare). Typically 1"-8" tall, it can extend 6'-9' in deep water.
  • Roots fleshy.
  • Flowers either male or female, small, and white; grouped into compact, 4mm-6mm globe at tip of stem.
  • Male Flower
    • Sepals 2, greyish, oblong-linear or linear-oblanceolate, curved, 1.5 mm long
    • Petals 2, triangular, nearly equal, 0.5 mm long
    • Stamens 4, anthers black
  • Female Flower
    • Sepals 2, grey, oblong to narrowly obovate, curved, keeled, 1.5 mm long
    • Petals 2, pale, oblong-linear to linear oblanceolate, 1.5 mm long
    • Pistil 2 carpellate
  • Seed light brown or red-brown, ovoid to broadly ellipsoid, 0.5 mm long.


  • Unmistakable in bloom; a tiny, white pinhead rising just above the surface of the waters.
  • Distinguished from the similar Water Lobelia (Lobelia dortmanna) by its leaf-less stem, and narrow, grass-like leaves. Water Lobelia has tiny leaves on the stem, and hollow, fleshy, blunt-tipped leaves in its basal rosette.


  • Labrador to Minnesota, south to North Carolina and northern Indiana.
  • Also Europe (Great Britain and Ireland).


  • Usually found growing in clear, shallow waters of lakes and ponds, on a bottom of sand or peat. Occasionally seen growing above the waterline on moist shores where a dry summer has drawn down the lake levels; also bogs and muskeg.
  • One of several species of aquatic plants (along with Isoetes spp. and Lobelia dortmanna), able to take up carbon dioxide from the roots. They are generally found in oligotrophic, acidic waters with extremely low dissolved inorganic carbon.





  • Reproduces by seed and vegetatively by rhizomes
  • Flowers July - September


  • By rhizome division,


  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Cultural Requirements
    • Full sun
    • Sandy/peaty, slightly acidic soil
    • Clear water to a depth of 4"-6"
  • Size 2"-3"W x 1"-8"H
  • Good for the clear shallows of natural ponds or naturalistic water gardens where they can grow undisturbed by pets and other critters.
  • Not known to be commercially available.



  • I will always remember my first sighting of a Pipewort in bloom, on a bright summer morning, just off the campsite on Muskeg Lake.

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Last updated on 26 February, 2004