Isoetes tenella

Spiny Spore Quillwort

Spiny Spore Quillwort, Isoetes tenella, Photo courtesy of USDA Plants
Spiny Spore Quillwort
Photo courtesy of USDA Plants

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


  • Isoetes, from the Greek,
  • tenella, from
    • Formerly echinospora, from the Greek 'echinos (echinos), "sea-urchin; hedgehog (Erinaceus europaeus)", and spora (spora), "seed"; hence "spiny seed"
  • Common name from the spiny leaves and the Anglo-Saxon word wort, "plant"
  • Other common names include: Spiny-spore Quillwort, Spring Quillwort (UK), Gulgrøn Brasenføde (Dan), Muda-Lahnarohi (EE), Vaalealahnanruoho (Fin), Mjúkur álftalaukur (Is), Stachelsporiges Brachsenkraut (Ger), Mjukt brasmegras (Nor), Poryblin kolczasty (Pol), Vekt braxengräs, isländskt braxengräs, taggsporigt braxengräs (Swe)


  • Kingdom Plantae, the Plants
  • Subkingdom Tracheobionta
    • Division: Lycopodiophyta
      • Class Lycopodiopsida
        • Order Isoetales, the Quillworts
          • Family Isoetaceae, the Quillworts
            • Genus Isoetes, the Quillworts
  • Taxonomic Serial Number: 507546
  • Also known as Isoetes braunii, Isoetes echinospora, Isoetes muricata, Isoetes setacea
  • Quillworts are considered by some to be the last remnant of the fossil tree lycopods, with which they share some unusual features including the development of both wood and bark, a modified shoot system acting as roots, bipolar growth, and an upright stance.


  • A small, lake-bottom relative of the ferns, with an ancient pedigree.
  • Leaves dark green, grass-like, elongated, up to 30 in number, up to 3½" long. Not typical leaves but sporophylls, bearing large micro and megasporangia embedded into the upper leaf surface. At the leaf base is a sac-like sporangium, containing the spores.
  • Stem a two lobe corm with much starch storage, very much reduced in size and no more than the bit of plant between where the leaves attach on top, and the roots on the bottom. Does not elongate, but will grow thicker with age; may even produce small areas of bark.
  • Roots are produced from furrows in the corm. Anatomically quite different from the roots of higher plants, some consider them to be modified leaves rather than typical roots. Thus, they are often referred to as "rooting appendages". This characteristic anatomy of rooting appendages is shared by our Isoetes with the long extinct fossil lycopods.
  • Fruit sporangia, borne within the swollen, paler base of each leaf.
  • Spores white or cream-colored with minute spines (viewed through microscope)


  • Identifiable as a Quillwort by its small size, multiple spiny basal leaves, and its habitat.
  • Distinguished from the closely related Lake Quillwort (Isoetes lacustris) by its much shorter leaves. Lake Quillwort leaves grow to 8" in length while the leaves of this species do not exceed 3½".
  • Field Marks
    • always submerged
    • short, spiny leaves in a basal clump


  • Newfoundland to British Columbia, south to Pennsylvania and California.


  • Sandy lake bottoms in shallow waters; rare. July-Sept.





  • By spores



  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Not known to be commercially available.



  • Look for these unusual "ferns" in calm, shallow waters over a sandy bottom. We found several of these just off our campsite on Frost Lake.

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Last updated on 26 February, 2004