GARDENING : TERRACES OR BERMS MAKE PLANTING POSSIBLE ON A SLOPE.

Byline: Joshua Siskin

No task is more challenging, more full of possibility and more daunting than planting on a slope.

My first experience planting on slopes occurred in a back yard in Saugus. It was planted with a few red-tip photinia shrubs, interspersed with trailing African daisy (Osteospermum fruticosum). Actually, this was not a bad planting scheme. The red foliage of the photinia was nicely offset by the white petals and purple centers of the African daisy. But the sprawling and mounding daisy had died out in large sections - as ground covers usually do after a number of years - and it was time to try something different.

I was dispatched by the property owner to the yard of a utility company, where my truck was duly loaded up with old telephone poles. The idea was to build terraces into the slope with the help of the poles.

Terracing a slope is basically a lot of shovel work. You start at the bottom of the slope and work your way to the top. At the Saugus site, we began by digging, at the base of the slope, a trench whose depth was equal to the diameter of a telephone pole. When we were finished, we could lay a single telephone pole, horizontally, in the trench.

Before laying the pole, we drilled holes at 3-foot intervals along its length and then drilled holes at matching locations on an equally sized pole. We slid 2-foot-long pieces of rebar into the holes of the first pole before placing it in the trench. Then we placed the second pole, horizontally, on top of the first, sliding it through the rebar which stuck out through the first pole. We backfilled soil from the slope so that it was level with the top of the second telephone pole.

This became our first terrace, and we continued to dig trenches and lay down our poles all the way up, creating terrace after terrace as we went. We might also have used railroad ties, as many landscapers do, to hold each earthen terrace in place.

Once terraces are constructed, the planting possibilities of any property are significantly enhanced. Tropical plants that might freeze when planted on flat ground often grow perfectly well on terraced slopes, since cold air rolls down the side of a slope just like water.

In the absence of terraces, planting on slopes is always a problematic enterprise. Without terraces, plants must still be placed in the ground vertically, and a crescent-shaped berm (hill of earth) built on the downslope side of every plant. Berms allows water to collect around new plants. Without berms, water runs down the slope, and the newly installed plants may die.

Sprinklers should be installed at an angle so that the water is sprayed parallel to the slope. Sprinklers should be situated so that they spray plants located above them on the slope, or at their same level. Do not rely on sprinklers installed along the top of a slope; their area of coverage is difficult to predict, and they overshoot the plants directly below them.

To create a hanging garden effect, plant trailing ornamentals such as prostrate rosemary on sunny terraces and blue periwinkle (Vinca Major) on shady terraces. When the hanging shoots of these plants are in bloom, they display a veritable sheet of color.

Almost any garden you can think of will grow on terraced slopes. Consider roses, herbs, wildflowers or fruit trees. Just make sure the terraces are wide enough so that you can access your plants after they have reached their maximum size. California natives, by the way, do especially well on slopes, since they crave the well-drained soil that slopes generally provide.