Don't think they're particularly fussed. Got the variety 'firetail' on order for the garden .

And I've got a 'Red dragon' that I have never looked after but I can't stop it. My neighbours now all have its kids.

I have 'Firetail', tough as old boots and will grow anywhere, I have it in complete shade and also in full sun, it flowers well in both conditions.

I have several forms of Persicaria, and it likes anywhere, but it ought to be large enough for it to spread without concern. Both my firetail and Southcombe white are about 6' tall and have spread to about 12' wide. and that is about 4 yrs after planting. My red dragon in partial shade is the beautiful dark red, but the one in deep shade is wonderful tones of olive green with maroon markings. both are about 8' tall, but not too wide.