San Diego is mainly a series of canyons and mesas, which means that many homeowners must contend with landscaping on slopes. But while successfully designing and installing a landscape on a slope is a huge challenge, it is also a potentially rewarding one. The issues that arise in relation to this challenge range from the difficulty of working on the slope–digging, walking about on it, and maintenance–to safety considerations, irrigation, and aesthetics. Because of these challenges, this will be the first of a five-part series. In this first installment, I will address aesthetic considerations from a natural perspecive.
A great way to think of how natural landscapes relate to cultivated ones is as raw material to finished product. One needn’t, nor probably shouldn’t, try and reproduce the full look of a native slope (unless your interest is in habitat restoration), but rather echo the local ecosystems in the designed landscape. Another way of saying this is that the designed landscape refers to or indexes the native landscape, but also sets itself up as its own entity. This thinking is originally Japanese, but it fits in well with modern sensibilities perhaps more comfortably than other aesthetics.
To see what I am talking about consider the following photograph of a native hillside in San Diego in late October. Keep in mind that this is the San Diego ecosystem at the end of its dormancy, the period just before rains start, so the plants look a little ragged:
Many people who see such a photo, or who see San Diego’s hillsides in the summer and autumn would be hard-pressed to find an aesthetic to work with given the overabundance of weedy looking, dried, dead, and brown foliage. But there is a lot more to appreciate here than dormant perennials and grasses. For one thing, the rocks provide an outstanding feature in defining the flow and curvature of the slope. The slope, it turns out, is anything but uniform: it folds into something of a gully, and the rock helps to define that.
The other outstanding element is the sugar bush (rhus ovata) that punctuates the vista at regular intervals with its beautifully-shaped evergreen leaves. It rises up out of the dormant plants in neat rounded shapes. So these are two elements that can be imitated in slope design. One needn’t use sugarbush specifically to create this effect. Its size makes it impractical for most of us. But its regularity and spatial properties provide inspiration.
Above is a simplified view of how this principle might apply to a slope in a residential neighborhood:
Sugarbush is probably too big a shrub for most landscapes, but the pattern can be reproduced with any number of medium to small-sized evergreen shrubs, creating a look that fits in nicely with San Diego’s native slopes.
A final caveat: the look as described above goes against the principles that are typically taught in landscape architecture, in which plants are grouped into masses. But this is most likely the influence of ecosystems from more northern places than San Diego on design principles , such as those found in England, for instance, where plants tend to grow tighter. But if one looks at gardening traditions further to the south, say, in Italy, or even further south, to Egypt, one starts to observe a much greater use of space and focus on geometry. And I would argue that this is the influence of the environment on people’s perception of what is aesthetically pleasing. Plants can only mass together when there is plenty of water to share, and if there is not a lot of it, they prefer to give themselves space.