Steep, small shady garden

You say a steep gradient - does it slope down from the house, or up? I only ask cos that makes a difference to what you'll need to plant to make it look aesthetically pleasing. And do you have any lawn, or want one if not?

And 15 feet wide or long - if you have a townhouse, you probably mean 15 wide and 20 long?

Spiggers there is no such thing as a 'maintenance free' garden no matter what you will have to do some work... Heathers might work but will need attention as they can get leggy quite quickly and wont give all year round flowers. The ones grown for foliage effect need a lot of sun to produce the really nice foliage. I'd suggest making sure the area is completely weed free, covering with a weed control membrane, cutting holes and planting small, alpine type, plants that will not need a lot of attention and topping off with bark - of course this does depend on just how steep the slope is. You will also have to take into account the two trees and their roots.

If you don't want to do any maintenance, then a variegated ivy might be good. this will cover the ground on a slope and look good all year. In August/ September buy a lot of daffodil bulbs (your choice of type) and plant them in drifts for spring colour...Of course you might get the gardening bug and then you could have all sorts of lovely plants!