West Highland Flora

Mackay's Horsetail


Equisetum x trachyodon

The hybrid between Variegated Horsetail and Dutch Rush

Equisetum x trachyodon

Photo John Birks
Dept of Biology, Univ. of Bergen
Aug 1980 Glenhinnisdale, Skye

Rare, beside fresh water

Stems to 100 cm high, c 2-6 mm diameter.  Cones c 4-5 mm long

ID: Intermediate between the parents.  Stems may be unbranched or with the odd branch from low down looking like another stem.  Like both parents, the stems have rough ribs each with 2 rows of tiny tubercles.  Sheath teeth have a fine hair-point; both teeth and hair-point persist until winter, then fall together.

Other features: The cone looks like that of Variegated Horsetail but is less developed, being sterile, and often remains partly included in the top sheath.  Sheath is pale green or grey with a black band at the top, eventually turning black all over.  Teeth have black centre line with pale edges, and may also become wholly black.  Number of stem ribs, or sheath teeth, is about 7-13.

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Equisetum x trachyodon

Photo John Birks
Dept of Biology, Univ. of Bergen
Aug 1980 Glenhinnisdale, Skye


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