If there’s one plant I can guarantee you’ll see more of this year it’s Persicaria runcinata ‘Purple Fantasy’. One of the foliage Persicaria tribe – this one a cultivar of a species native to the eastern Himalayas – it’s easy to grow in full sun to part shade and creates and exciting, attention grabbing focal point.
I’ve grown Persicaria ‘Purple Fantasy’ in our little garden for a good number of years now and it’s one of two plants on our NGS open days that every single person asks about. Fairly rare a number of years ago I now see it being offered by mainstream plant companies and it’s been planted in huge swathes in RHS Wisley’s new tropical garden.
The main things to know about the plant are that it grows best in some sun though can handle a fair amount of shade. Persicaria are tough, vigorous plants, after all they are the knotweed family, related to the feared but much bigger Japanese knotweed. It’s a hardy plant too, dying back in winter, with new shoots emerging with the warmth of April.
While many Persicaria are grown for their flowers, this and others like P. ‘Purple Dragon’ are grown for their leaves. They do flower but they’re tiny little white things and best ignored or removed. By the time they flower the can be quite leggy and tall, and even begin to lose some of those dark chevrons as they fade to green. At this point, I cut might down almost to the base and it will spring back within a couple of weeks with fresh flower-free foliage.
So tough is this Persicaria that you can slice out a chunk to form a new plant at any point of the year and it won’t bat a leaf. From a tiny one shoot plant, by the following spring you will have a colony of shoots at least 50cm x 50cm. By the following year four times as much. It’s quite a vigorous spreader but easy to control by digging out large chunks to reduce its size in winter or early spring and binning (or giving away). From my one tiny plant I have started entirely new colonies in about five of my garden designs for clients.
As you can see above, it grows well in pots of any size as long as you can keep up with the watering. I’ve grown mine in the same 25cm pot for over four years now simply by unpotting it in early spring, slicing into quarters and repotting one quarter for that year.