Fallopia x conollyana

This taxon was first discovered in Leicester in 1982 when we checked some seed collected from the ordinary female F. japonica at our standard site at Oadby Race Course.  The seedlings that readily grew from this seed had narrower pointed leaves with somewhat cordate bases and had a twining habit, quite unlike F. japonica.  The chromosome count was a complete shock;  I could put one count of 2n=54 down as some sort of meiotic abnormality, but when it got to three I began to wonder.  A wider survey revealed the same phenomenon was occurring throughout Britain!  I then got to thinking that if we were dealing with a normal fertilization event, the female F. japonica would contribute 44 chromosomes leaving 10 to have come from the male parent. This meant we were looking for a twining plant with 20 chromosomes.  It did not take long to point the finger at the commonly grown garden plant Russian Vine (Fallopia baldschuanica) which had a chromosome number of 20.  Artificial crosses were made, and the resulting plants matched perfectly those derived from seed on the open-pollinated F. japonica from around Britain.  Fortunately, these hybrids do not combine heterosis with the combined vigour of their parents, otherwise we would really be in trouble!  The probable reason for this is that these two species have conflicting growth and storage strategies. F. japonica is herbaceous and dies down every autumn and stores its reserves in stout underground rhizomes.  F. baldschuanica on the other hand is a woody perennial without rhizomes and stores resources in the persistent woody shoots.

On account of its increased and widespread incidence it was recently given an official hybrid name - it is named after Ann Conolly of Leicester in recognition of her contribution to research into Japanese Knotweed over the years.

This shows the leaf shape and arrangement of the hybrid F. x conollyana


F. x conollyana is often shy of flowering, but this clone from Hungary flowers regularly

Bailey,  1992 & 2001

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