Looking for affordable suggestions for planting out a 5 metre stretch of vertical bank (about 85deg slope, 1.5 metres high) that has existed for 90 years with no major problems as far as I knw. Has had ferns and some succulents planted, as well as a scrubby tree or two, but some of the clay/soil is beginning to crumble. Need suggestions that won't encroach on the pathway and are easy-care!

Dunedin, New Zealand.