Equisetum x meridionale Southern Horsetail RRR D N
This is a very recent addition to the British flora which has happened some time after its discovery was first published in 2000. It was at first incorrectly identified as E. x trachyodon (Mackay's Horsetail). E. x meridionale is the hybrid between E. variegatum (Variegated Horsetail) and E. ramosissimum (Branched Horsetail) while E x trachyodon is the hybrid between E. variegatum (Variegated Horsetail) and E. hyemale (Rough Horsetail).
The differences between single stemmed hybrid horsetails can be slight and could require examination with a good hand lens or microscope but there is only one not very obvious difference between these hybrids which you can see see without a hand lens: : the degree of main stem branching. The E. x trachyodon I have seen, rarely produces branched main stems while E. x meridionale is quite obviously branched probably reflecting the E. ramosissimum parentage.
However the diagnostic difference is not the relative degree of branching but the presence or not of silica cross-bands on the flat topped stem ridges of E. x meridionale. These are small horizontal faint white marks and hard to see with a x 20 lens but it is just about possible. E. x trachyodon doesn't have these cross bands.
There is a good deal of Equisetum x meridionale at the Anglesey site and judging by the debris under the main foliage it has been present for decades unnoticed. However this is not the only site in the British Isles for this hybrid - there are several sites on the Wirral in the Vice County of Cheshire. A full acount of the discovery and renaming of this Hybrid Horsetail can be found here:
New Journal of Botany Volume 3 Number 1 April 2013
Hybrids within Equisetum subgenus Hippochaete in England and Wales
by P Jepson, M Lubienski, P Llewellyn and R Viane
E x meridionale is present at sites on continental Europe but is not common there either.
|
|
| Equisetum x meridionale | Equisetum x trachyodon |
LHS: Near Valley Airfield, Anglesey, 22nd June 2010 RHS: Red Rocks, Wirral, Cheshire 15th June 2010
Added on July 3rd 2010, updated July 30th 2011, updated 30th August 2014