West Highland Flora

Field x Marsh Horsetail


Equisetum x rothmaleri

 

Equisetum x rothmaleri

Photo John Birks
Dept of Biology, Univ. of Bergen
Aug 1992 Kilmuir, Skye

Very rare.  First world discovery was in Skye in 1972, not found elsewhere in British Isles till 1987 and still not known from outside BI as of 1997 (Stace 2nd ed).  May be overlooked however as both parents are very common and don't normally get the close examination they'd need to reveal the hybrid.

Cone c 4-9 mm

ID: Intermediate between Field Horsetail and Marsh Horsetail.  Stems have whorls of branches, stem grooves 6-12.  Lowest internode of branches is about as long as the stem sheath, whereas in Marsh H it is much shorter and in Field H usually longer.  Branches have 4-6 ribs (Field H always has 4, Marsh 4-6).  Branch teeth have black tips (black in Marsh, green in Field) which are spreading (as in Field) rather than appressed to the branch (as in Marsh).

Other features: Cones are borne on the ordinary green shoots, as with Marsh, not on separate brown shoots as in Field.  They are sterile and do not expand like the cones of the parent species.

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Equisetum x rothmaleri

Photo John Birks
Dept of Biology, Univ. of Bergen
Aug 1992 Kilmuir, Skye


Back to species list