For British gardeners the RHS Plant Finder reveals which of over 600 nurseries stock each of 70,154 plants. But for gardeners around the world the RHS Plant Finder has wider value as the fount of all wisdom on correct plant names. Overseen and regularly updated by a team of horticultural botanists based in Britain but with connections around the world, the team and its associates look at the naming of plants at all levels.
So the Plant Finder will confirm that the correct name, accepted around the world, for the dreaded Japanese knotweed is not Polygonum cuspidatum nor Polygonum reynoutria nor Reynoutria japonica but is Fallopia japonica – which reflects its close botanical connection with the rampaging mile-a-minute vine, Fallopia baldschuanica. (Fallopia baldschuanica, by the way, is the correct name for what has been called Bilderdykia aubertii and half a dozen other names.)
This year, after much deliberation, the team has accepted the splitting from Dicentra of a number of species and elevating them into genera of their own. So the yellow-flowered climbing types are moved into Ichthyoselmis and Dactylicapnos and a favorite spring perennial, Dicentra spectabilis (left, click to enlarge) – in full flower now, frost permitting – has been elevated into the genus Lamprocapnos. They have not yet decided to accept the splitting of the American members of the genus Aster into many smaller genera.
But perhaps the most startling of this year’s changes is the transfer of Antirrhinum, Digitalis, Hebe and Penstemon to the plantain family (Plantaginaceae) – which most of us know as wind-pollinated weeds. They may look so clearly very different but the reason for this, and a number of other changes, is explained in a new essay written by RHS Chief Scientist Dr John David. Basically, it’s all down to the analysis of the plants’ genetic material (the genome). Verbascum and Phygelius, by the way, remain in their original family (Scrophulariaceae) where they are now joined by Buddleja.
The essay, although rather long and a little technical for the casual reader, is well worth reading for its overview of the changes at family level.
Name changes will continue. The one downside of the Linnaean system is that when we discover more about the way in which plants are related to each other, the names have to change. At least with the free online RHS Plant Finder we can easily find out what the correct names are.
And you can find out more about the changes in Dicentra in the excellent book from Timber Press called Bleeding Hearts, Corydalis, and Their Relatives. It's very welcome to finally have an opportunity to recommend this invaluable book.