I can't see any old stem at the base of the plant in the previous photos. If it was horse chestnut I would have expected to see some old stem, they don't grow that quickly from the ground unless they can grow from the roots or part of the trunk which might be under the surface level.
The colour doesn't look right either, horse chestnut is more green even when young, although I have discovered a colourful cross.
https://www.google.co.uk/searc...
Rodgersia is still on the cards, I'm surprised most leaves are still curled under at the edges. I looked for mine but it hasn't shown itself yet.
