I think they get plenty of goodness from the humus. The trees in woodland drink up all the available water and food - but the woodlanders get there first by being fibrous-rooting and on the surface where they can get their goodness from the rotting down debris before the trees. clever things!
If planting anew in woodland - then it might be useful to give each plant a handful of compost/manure in its planting hole to start it off.

I give all my plants a feed of bonemeal every year and they seem to like it. It is a shrubbery rather than a woodland though

i dont add anything [except leaf mould] to the ones already established. new ones get plenty of leaf mould in the planting hole when i plant, I top dress with leaf mould as the fresh leaves get lifted in the autumn i then compost them.

I would not put manure round hellebores Jonathan

I'll just save it for my roses then. They gobble. It seems from what you all say that hellebores like quite low fertility. I have no leaf mould to add, but can top dress with multipurpose compost to aid humus content. It's perfectly economical in a garden as tiny as mine. I put rotted manure around all my shrubs. Would I be right to asssume it is suitable to spread around most perennials generally also?

Um... no not really

I'll save it for my roses only then.