Need Help?

Allan designs and plants flowering gardens in Montreal, Zone 5 [USDA Zone 4] .

See website, design work and favorite flowering plants at

Consultation and coaching for do-it-yourselfers is provided. Occasional emailed questions are welcome and answered free of charge. Oui, je parle francais.

See my work on Pinterest at Garden Guru Montreal

Entries in Dianthus Carthusianorum (3)


Transparent Perennials in the Flower 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.


News From the Test Garden

The image posted in August showed a close up of this intensly pink Dianthus.On August 14, 2009 I wrote about a new plant discovery that I had made at one of my favorite nurseries, Jardins Michel Corbeil, in Ste Eustache Quebec. There I found Dianthus Carthusianorum. When I first planted it in July, I had read on-line about the concerns of some gardeners who were anxious about combining it with companion plants. The challenge was the tall slender stems that create empty spaces between the flower heads and the base of the plant.

Well here we are three months later and I am pleased to report that there is no need to be concerned about its placement. The fuchsia-pink of the flower heads is so intense that one should grow this plant just for its color. It looks great even without companion plants; it doesn't need a supporting cast to put on its show. Delicate and small as its flower head may be, it is an attention grabber. Plant it where it can be seen and admired.

This plant was in full bloom when I purchased it in July and it has been flowering non-stop since then. Three months of flowering is a perennial gardener’s dream. The best gift of all, though, would be to see it reappear vigorously next season. I often worry about perennials that are destined for zone 5. Some are unable to tolerate severe winters. Only time will tell.

Click here to view a close-up photo of this vivid perennial.


Dianthus Carthusianorum: a Little Known, Hard-to-find, but Hard to Beat Perennial 

Nature has given me a challenge. I have discovered another unusual perennial and I need to learn how to use it effectively in the garden. The nursery that stocks this plant recommends it as a “must” for the English garden look. However, incorporating it into a garden composition will not be an easy task.

What sets this plant apart from all other Dianthus is its relatively tall flower stalks. Small but extremely intense fuchsia-pink blooms sit on top of thin reed-like stems arching 28 inches high. This is the tallest Dianthus that I have seen so far and finding appropriate companion plants for it has become a challenge.

It is clear from studying the slender stalks that this perennial will need substantial looking companion plants to fill the negative space between its stems. Some suggest that Campanula latifolia Brentwood would be an ideal choice because the intense purple of its flowers running up and down its stalks creates a richly colored backdrop. Others say that Brentwood is too coarse looking. I will need to do further research and some old-fashioned experimenting to discover my options. Perennials with a rich shade of purple either in foliage or in flowers will be considered and I will experiment with white Liatris, Veronica Sunny Borders Blue and Salvia Caradonna.

This perennial blooms from July to September in zones 5a to 9b in full sun. Like most unusual perennials it is not easy to find. I found mine at Jardins Michel Corbeil in Ste Eustache, Quebec.