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Reticulation between Helosciadium repens (Jacq.) W.D.J. Koch and H. nodiflorum (L.) W.D.J. Koch (Apiaceae) has been the source of much speculation, but until now supporting evidence has remained largely anecdotal. In the current study inter-specific hybridisation and introgression between the two species was confirmed using DNA barcoding. The parentage of three putative hybrids collected from Port Meadow, Oxfordshire (UK) was determined using a maternally-inherited chloroplast marker (rps16-trnK) and two biparentally-inherited nuclear markers (LEAFYi2, ITS). Two of the individuals are early-generation hybrids between H. repens and H. nodiflorum, F1 or otherwise, while the third is most likely a backcross to H. repens. These individuals are the first confirmed hybrids/hybrid derivatives between the two parental species, and represent a new addition to the British flora. The hybrids closely resemble H. nodiflorum var. longipedunculatum F.W. Schultz, and in our view should be treated as H. × longipedunculatum (F.W. Schultz) Desjardins.

The occurrences in Denmark, Britain and Ireland of ×Elyhordeum langei (Elymus repens × Hordeum secalinum) are documented, and the variation in this hybrid is described. The French hybrid ×E. rouxii is also briefly covered. The discovery, distribution and characters of a new hybrid, E. caninus × H. secalinum, first found in North Lincolnshire, England, in 2014, are described and discussed. Cytological and molecular studies are included. The latter is described as ×E. kirbyi M.P.Wilcox, hybr. nov.

A large clone of a Petasites found growing at Borde Hill, East Sussex in 2014, which had been identified as female P. pyrenaicus (P. fragrans), otherwise unknown in Europe as far as we are aware, has been shown by morphological and molecular studies to be the hybrid female P. japonicus × male P. pyrenaicus. The origin of this hybrid, new to science, is unknown, but it has evidently been growing at Borde Hill for several decades, and has now escaped into the wild beside an adjacent footpath.

Helosciadium × moorei (Apiaceae), collected from County Cork, Ireland, is confirmed as an interspecific hybrid between H. inundatum and H. nodiflorum. The origin of this taxon was investigated usin...