Equisetum x trachyodon is a hybrid, single stemmed horsetail with parents Equisetum hyemale (Rough Horsetail) and Equisetum variegatum (Variegated Horsetail). As with any Equisetum hybrid there is no need for either parent to be found anywhere near the hybrid.

There are only two confirmed sites for this hybrid horsetail in England which unfortunately has been confused with Equisetum x meridionale at a number of sites for many years. The problem is entirely understandable: Equisetum x meridionale was not even considered as it was thought to be absent from the British Isles. Not known from the British Isles until a few years ago, it was found on Anglesey having previously been misidentified and reported in Watsonia as Equisetum x trachyodon.

Now (July 2011) all English sites have been re-assessed and the only ones with true Equisetum x trachyodon are in the far north of England near Carlisle and by Chirdon Burn in the Kielder Forest. And for those interested in going there to see it at these sites - good luck. These are two of the most difficult and inaccessible sites it has been my midge-ridden, fly-blown displeasure to try to find. Drive to Skye - it's much easier.

The two Equisetum hybrids species (E. x meridionale and E. x trachyodon) do look very like each other. Both grow as single green stems like their single stemmed parents. There is significantly more branching with Equisetum x meridionale than Equisetum x trachyodon as you might expect with its Equisetum ramosissimum (Branched Horsetail) parentage.

But the character which really distinguishes the two is hard to see even with a good hand lens. Equisetum x meridionale has silica cross bands on the flat topped ridges of the stems (inherited from Equisetum ramosissimum) and these just about show as faint horizontal white marks with a x 20 lens. Even then they are not always clear. Equisetum x trachyodon has no such banding. The two stems look the very much the same even with a x 10 lens. Really you need a microscope.

Both hybrids have rows of white dots parallel with the stem ridges running longitudinally up the stem which is a sign of the other common parent Equisetum variegatum.

As well as the two confirmed sites near Carlisle and in the Kielder Forest near Bellingham, there are a few sites in Scotland but only on the islands or north of the main industrial belt cities. In Northern Ireland though it is found frequently also occasionally in the south.

LHS and Mid: Banks of Chirdon Burn, Allery Bank nr Bellingham RHS: Bank of River Black Lynne nr Carlisle 27th July 2011, updated 11th Nov 14

Added on 29th April 2005, updated 2nd January 2009, updated 29th March 2010, updated 3rd August 2011