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

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Entries in perovskia (3)


A Tale of Two Tall Plants

Vernonia noveboracensis, I discovered Vernonia noveboracensis last year, my excitement was fueled by the height and color of the plant. Only a handful of perennials grow as tall as this one does, [ 6-8 ft. (1.8-2.4 m)] especially at the end of summer, when most lofty plants bloom in gold or yellow. I found it at the nursery, lying on its side like an invalid, because it had outgrown its seedling-sized pot and was root bound. It was planted in my garden in August of 2009, with an expectation that it would establish itself and deliver impressive results by August 2010. That did not happen. Clearly, this infant perennial needed more time to mature and its lack of presence in my garden a year later was disappointing. One tall stalk grew where I had expected several and that stem had only a modest amount of branching florets. Part of my disappointment lay in the fact that the color of its blooms, a muted violet magenta, does not have the brilliance to project itself over long distances. I came to the conclusion that unless one admires this plant up close, it makes no statement at all.

Vernonia only looks this rich in photos. image: negative impression was short lived. A few days after it bloomed, I began my vacation and found myself in a public park in downtown Zürich where Vernonia was the star attraction. What a shock to see this plant at center stage. It had been planted as part of a larger flower composition, now mostly gone to seed, and remained the only perennial still in bloom. To my surprise, it looked impressive. A long row of twelve mature Vernonia formed a lush backdrop to the original composition. What I learned in Zurich is that this perennial can be visually effective when it is mature, with many brackets of blooms, and when planted in drifts. Distributing plants in drifts is a garden design technique that produces dramatic results. However, it requires architectural perennials like Vernonia that can also supply winter interest. The challenge, going forward, is to find a way to incorporate drift planting into small residential gardens.

A combination of Vernonia, Water Canna, and Eupatorium. Photo by Joe Henderson for Chanticleer Gardens, Pennsylvania, the time I returned home, my own Vernonia florets were spent and I decided to leave them uncut so that I might be able to differentiate this plant from other spent stalks that grew nearby. That decision turned out to be wise because later in autumn, the Vernonia dead heads morphed into cinnamon-colored feathered seed pods that shimmered in the sun. This visual and textural interest was a bonus that I could have never imagined.

Boltonia. The flowers in my garden never look this pink. Photo: the far end of my garden, another story was unfolding where only a few months before I had planted Boltonia. In my never ending search for tall perennials, I purchased a seedling at the nursery in order to experiment with it in compositions. For many years, I had seen this plant in other gardens and never found it attractive. It reminded me of a giant weed. Even the pink color of its flowers looked insipid in the sun. What an irony that a plant should be so distorted by the very thing that it needs to survive. Nevertheless, I had wanted to see how it would perform in my garden setting and had hoped to be inspired by its height. It did no better in my garden than it did in others. Even though it was tall [4 to 5 feet] and architecturally majestic, it remained unimpressive in bloom. That it needed to be staked early in its growth, just like a Delphinium or Aster Alma Potchke, did not earn it high marks either.

PerovskiaHowever, it did occur to me, that if I were to lift and move it to the other side of the garden, in front of or behind Vernonia, perhaps the two plants might enhance each other. I am trying to imagine if the juxtaposition of pale pink and violet magenta will help improve the color projection of both plants.


Helianthus, photo Lone Willow Farms I am also inspired to add silver blue Perovskia in front of the Vernonia and lemon yellow Helianthus nearby. The possibility that I might generate color synergy between the four perennials intrigues me and I have placed that project on my to-do list for next season. It’s a wonder how these ideas keep percolating upward now that it is too late to act upon them until next spring.


Effervescent Perovskia, the Perfect Perennial

Capturing the shimmer on this plant eludes most photographers. You will have to grow it to experience the shimmer. This photo is supplied by Lotus Greenhouses. Click on the image to visit their site.

This is the champagne of all perennials. It literally shimmers all summer long. When fully opened, the flowers are lavender blue and brilliant in the sunshine. In bloom, this plant looks like a majestic silver-blue cloud; a veritable purple haze!

Perovskia grows into a multi-stemmed clump with flower panicles at the end of each stem.The finely-cut silvery grey-green foliage is intensely aromatic all season long. In the early spring its woody stems need to be cut down to 6 inches from the ground. It can also be trimmed in the fall but then one would lose the winter interest that the spent flowers offer.

This perennial is easy care and does not like to be moved or divided. It will grow to 4 feet tall and 3 feet wide, is happy in zones 5a to 9b, loves full sun and above all, adds rich character to the garden from July until fall. Heat, drought or humidity will not affect the performance or the beauty of this versatile perennial. Use it as a foil for other plants, especially pink rose bushes. Plant the annual verbena bonariensis in front of Perovskia and the combination will take your breathe away.


Web Photos That I Like

This photograph demonstrates how critical it is to pay attention to the spacing of plants and the location of sun when planning a perennial garden. The key plants in this composition are tall pink Eupatoreum in the background and silver-blue Perovskia in the front of the border. The annual, Verbena  bonariensis, separates the two. In this picture, Perovskia appears to be growing horizontally instead of upright and stately as it is known to do. Usually a composition of pink and silver blue is eye-catching because the two colors play off against each other. It is less successful when Perovskia kneels to find the sun. What appears to have happened here is that Perovskia is being crowded out by the plant behind it and is not receiving full sun all day long. Instead, as the sun moves away from this composition, the Perovskia bends over to follow it. Many gardeners are content to leave this composition as it is and to enjoy the casualness of the composition. Those that insist on a neater looking garden, or who want the pink and silver-blue to be closer together, will stake Perovskia to keep it upright. Being a vigorous plant, strong stakes will be required. In the left foreground of the picture, the silver-green low-growing plant is Sedum. This photograph was taken at Kilmalu Gardens on Vancouver Island, British Columbia.