Anita Morton - Growing Gardens
The slippery slope
Many gardeners have to cope with sloping ground, and some of us end up permanently longer in one leg due to the precipitous angle of our gardens. Terracing is the only complete solution, but it can be extremely expensive. Steep slopes require tall retaining walls which should be designed by an engineer seek qualified advice before installing any wall over 80cm tall. Dont exceed this height if doing-it-yourself, as collapsing retaining walls can be very dangerous. If you are at all uncertain about your project, consider hiring a qualified and experienced landscaper to advise you.
However, there are a few options which dont alter the contour of the ground. You still have a slope, but it will be easier to garden on it. Ive used long logs of regrowth camphor laurel, held across the slope by pegs made from reinforcing steel (deformed bar). These logs slow down the streams of water that run down the slope in wet weather, giving it a chance to soak into the soil. They retain any soil that erodes from the surface, as well as leaves and mulch etc. It is also much more secure underfoot when planting and weeding.
Less steep slopes can benefit greatly from a thick layer of mulch, held down by chicken wire. You will need to peg the wire down securely cheap tent pegs will do the job in heavy clay or stony soil, while all you need on softer soil is some hairpins of heavy gauge wire. Whichever method you use, the aim is always to retain organic matter and water, rather than having it all flow to the base of the slope. As you establish plants on the slope, their roots will play an important role in retaining the soil. Choose perennials and shrubs to reduce maintenance on an awkward site.