Another idea for the sloping site would be to use dogwoods – different varieties of Cornus. This would create a leafy bank, with soft greens and whites, and coloured bark in the winter. Growth could and must be controlled by pruning early in the spring. But I wonder if the site is damp enough? And is this the right ‘image’?
Cornus stolonifera ‘flaviramea’ (www.wildchicken.com)
Cornus Alba ‘Elegantissima’ (www.pflanzmich.de)
Cornus ‘Midwinter Fire’ (www.wyevalegardencentres.co.uk)
Cornus ‘Flaviramea’
And what about the need for colour? Perhaps low-growing mounds of colour?
Leucanthemum ‘Banana Cream’
Alchemilla Mollis
Sedum ‘Autumn Joy’
Nepeta ‘Walkers Low’ (www.crocus.co.uk)
You may be interested in
Dogwoods
Cornus ‘Flaviramea’
space
I’ve grown various types of the red- and yellow-twig dogwoods in previous gardens in regular soil as well as badly-drained ones, and found them to do pretty much the same in both situations. In fact there’s one (Elegantissima) here at the Temporary Garden which only gets whatever water Mother Nature provides and if anything the soil is on the dryish side. And with lots of root competition from adjacent conifers, euonymus, etc as well.
Yes, I like Elegantissima too and find it quite tough, but the ideas are for a friend who has to choose the style she would like to have… I am just making suggestions.