Japanese knotweed seeds

This time of year is a good time to look out for seed on Japanese knotweed, particularly around urban areas. Japanese knotweed in Britain comprises female plants and it is often stated that here it does not reproduce by seed - which is true. However, it does produce fertile hybrid seed, which can be grown on by the interested naturalist.
The plant hybridises with `Russian-vine` Fallopia baldschuanica (or `the mile-a-minute plant`) - a very rampant sprawler which is sometimes grown in gardens. One would think that the hybrid between Japanese knotweed and Russian-vine would produce a monster plant, exhibiting `hybrid-vigour` and with the propensity to take over Swansea and the world, but it does n`t!

The hybrid is a floppy-stemmed weakling which is rather sensitive to frost -the plants that I grew in 2006 fell victim to mild frosting, so there is no danger of creating a `Frankenstein plant`! The hybrid is named Fallopia x conollyana to honour the late Ann Conolly who did much work on Fallopia/Reynoutria. I seem to recall that the hybrid has been recorded `wild` once or twice in Britain, on industrial wasteground in an English city -  if I remember correctly.
The attached photograph was taken today at Furnace, Llanelli.
For those into hybrids, Fallopia x bohemica ( the hybrid between Japanese and giant knotweed, F. sachalinensis) grows on wasteground near the railway line at Cockett, Swansea SS633949, with plenty of the hybrid horsetail Equisetum x littorale on the northern slopes of the nearby Cockett Church, SS632948.