What about Hemerocallis, Penstemnon, Campanula persicifolia, or Salvia.

One of my favourite long lasting flowering plants in my garden is Geranium Orkney Cherry.

Kniphofia are long-flowering and I love Astilbe arendsii 'Fanal' which although not particularly long-flowering, has lovely bronze seed heads through the winter. I'm trying to thing of things with a similar colour of bloom to your persicaria, although you haven't said whether that is important. Geranium phaeum Samobar is lovey and a great maroon colour. And I have a lovely red-leaved and dark red flowered hydrangea which is beautiful both for foliage and flower. It's called Red Angel, but there are other red leaved Hydrangeas on the market. Astrantia 'Hadspen Blood' is a terrific plant as well. Or what about some evergreen winter interest with a dark red flowering Helleborus. Or a Dark red leaved Heuchera. Good luck getting the Persicaria all out! ;)

Thank you....lots of suggestions there....I will take a look. It is a thug to get out but we'll on its way !

Rudbeckia and/or Coneflowers and/or Gaillardia and/or Helleniums and/or Day Lilies.

I wasn't sure just where the Persecarias were but if near the front how about one or two Hebes. Some of them flower for a long time and they are all small evergreen, & some are variegated. Also they look after themselves, except perhaps after some years they appreciate trimming back a bit to stop them getting leggy and bare bottomed, lol. And they don't spread...

Thanks again for everyone's suggestions.

The suggestions I gave you are from my own garden which I enjoy very much. My garden is never without something or other in bloom. Except for day lilies, they all make great cut flowers for indoor arrangements. But day lilies are edible so its got that going for it. lol