Swales is a word I learned yesterday when reading Ken Druse’s new book – “The New Shade Garden, Creating a Lush Oasis in the Age of Climate Change”. My plan was to look up the definition, but before that was accomplished, my postal carrier delivered my current copy of Fine Gardening magazine – which had an article on swales, complete with drawings. How very convenient!
Essentially, swales are the low areas between ridges, meant to contain rainwater until it can soak into the earth. These ridges in my gardens, or berms as I call them, are made of silt clay excavated from my own property, formed into ridges, and compacted by stepping on them to help them become more solid. I choose to backfill the swales with chipped leaves, which sometimes move around the gardens during hard downpours of rain and deep, standing accumulations of rainwater.
Behind the hosta on the left, you see where a swale was excavated to route rainwater into this bed. Moving your eye to the right, you will see a berm, then another swale, then another berm, then another swale. This view shows the look of the berms before they were backfilled with chipped leaves to give the surface a more even look.
The same area, after a heavy rainstorm, shows the water being held in place so it can slowly soak into the earth. These swales were created to slow the downhill movement of rainwater. Photos fail to show the grade of slope, but the grade is enough to cause rainwater to gain momentum and leave the property, if not slowed by clay berms or retaining walls.
Another look at this area, more clearly showing the separation and slowing of rainwater. These pools of briefly-standing water are very precious to the moisture needs of the gardens.
Inside the fence along the back of the gardens, a taller clay berm. On the left side of the picture, you can view the organic debris that floated and gathered at the edge of the rain garden pooling area. Without this clay berm in place, all the good organic material would have washed down the hillside and been carried away by the waters in the creek.
This pathway behind The Cosanti Bed is naturally filling in with fine, rich organic material because it is a low area. Instead of continuing to rake away the organic material after each storm, I have decided to fill it with the new supply of chipped leaves that will become available this fall. It will always remain a pathway, but will have the chipped leaf surface like The North Trail pathway. This cover of mulch will also increase moisture for the azaleas along the sides of the pathway, for a few extra days following each rain.
Gardening knowledge is endless. Learning new words, techniques, and gardening science in general, keeps the gardener’s mind busy – and happy!