We have 3 hugh pine trees on a slope into the valley between our neighbour and us. It is bare except for the hostas that we have recently planted. When there is heavy rain, our roof gutter overrflows and washes the soil into the valley. What sort of ground cover would be best for easy maintenance in this shady clay soil area. See picture.
Hello and thank you for writing Toronto Master Gardeners with your question. Unfortunately, there was no picture attached. If this answer isn’t useful for your particular situation, please write again and include the picture.
We have a couple of gardening guides that might give you some ideas:
Broadleaf Evergreen Ground Covers
Perennials for Shade in Dry or Moist Areas
The Ground Cover Fact Sheet recommends Vinca minor (Periwinkle) and Pachysandra terminalis (Japanese spurge) for full shade, but they also prefer moist soil. For dry shade, think of Barrenwort (Epimedium), Geranium (Geranium macrorhizum), Spotted bellflower (Campanula punctata) or, my personal favourite, Sweet Woodruff (Gallium odoratum syn Asperula odorata).
Sweet Woodruff makes a low mat of small thin green leaves and grows in semi to deep dry shade. Tiny white flowers cover it in May. Care: rake away dead stems and add 1 cm compost in early spring.
Planting vinca ground cover is not recommended anymore as it can be invasive if there is adequate moisture. I have it under some huge spruce trees and it is doing ok there but not growing wildly because the ground is very dry. Certainly if your garden abuts a natural area, park, or ravine you should not plant vinca in case it escapes the confines of your garden. There is an excellent resource titled Grow Me Instead put out by the Ontario Native Plant Council which lists a number of native ground covers.