Garden designers use plant forms the way a painter used brushstrokes. In their book, Designing with Plants, by Piet Oudolf with Noel Kingsbury, six forms that are basic to flower compositions are identified. One of them is called screens and curtains. This double concept refers to the transparency of some plants whose form is mostly air. Unlike others that have a solid shape, transparent plants have an open network of either stems or very narrow flower spikes. These open spaces, also known in the study of design as negative spaces, allow one to look through the plant to admire flowers growing behind. According to Mr. Oudolf, such plants create ….effective combinations of color and form as well as an atmosphere of mystery and romance. In their book, the authors suggests eight such plants but I have found two more that work well in small gardens.
The two perennial that belong in this category are Dianthus carthusianorum and Allium schoenoprasum, two underused, and hard to find plant. These flowers are among my favorites because of the intensity of their pink color. Before discovering the concept of transparency I had difficulty combining these plants with other perennials. Now, I understand that they must be used as atmosphere, as open clouds, to subtly punctuate the garden design.
While engaged in online research for a previous blog on the RHS Chelsea Flower Show, I came across the above photo that imperfectly demonstrates how these two perennials may be used as screens to enchant the plants growing behind. It’s not the most effective example, but it is the best that I have found to date.
In pre World War Two movies, leading ladies would sometimes wear a hat, with a net veil that screened their face. The net created a feeling of mystery and transformed female screen actors into more fascinating characters. Transparent perennials serve the same purpose in the garden. The beauty of other plants is enhanced when they are veiled with curtain plants. According to Mr. Oudolf, the trick for successfully using a transparent plant is to give the illusion that it is planted everywhere, when in fact it is not. Over planting it adversely affects the overall composition.