"Don't be fooled by the crowds milling around the rose beds." That's gardener Akemi Sugii's perplexing heads-up for anyone planning a visit to next week's open days of the Ark Hills rooftop garden she manages in Tokyo's upmarket Akasaka district.
High life: Gardener Akemi Sugii tends some of the plants in the native- species section of the Ark Hills rooftop garden (top), while in another section tulips bloom (above). YOSHIAKI MIURA PHOTO
That's because, Sugii says, the high point of her handiwork is not to be found in the showy ranks of red, white, yellow and pink roses, but in a far more subdued section of the garden dedicated to plants native to Japan and East Asia.
Sugii is one of many horticulturists and environmental activists in Japan calling for increased use of native plants in gardens and landscape projects.
Some argue the shift is necessary for ecological reasons — native plants can't compete with fast-spreading alien imports such as Giant Ragweed (Ambrosia trifida), for example, which now dominates great tracts of land beside the nation's highway network.
However, Sugii's reasoning is more positive — and directed specifically at private gardeners.
"Japanese people have fallen in love with English gardens," she said, so when it comes to which plants to put in their backyards, they tend to go straightaway for roses and tulips. "But gardening is a type of amusement," she observed with a smile. "And it's more fun to have more things to play with, right? So why limit the type of plants you use?"
The Ark Hills rooftop garden actually occupies several rooftops — mostly those belonging to the gracefully stepped Suntory Hall. The native plants occupy one of the steps — an area of about 600 sq. meters — and the roses another. Standing in among all that greenery, it's easy to forget you're in the middle of Tokyo.
Pointing out a stand of low-growing isogiku (Chrysanthemum pacificum), with its white-rimmed leaves, and fragrant kawara nadeshiko (Dianthus superbus), with its delicate purple flowers and elegantly slim leaves, Sugii explained that native plants such as those are not as likely to "overwhelm" viewers as a big gaudy flower might — but nevertheless they possess a "quieter, more calm" beauty, generated largely from the pretty shapes and colors of their leaves.
Another advantage of natives, Sugii noted, is that many are resistant to strong winds, making them suitable for use on exposed urban balconies.
She also confided that a clue to assessing the hardiness of a plant is often hidden in its Japanese name. "Names that have references to the ocean or water indicate that the plants thrive in those environments," she said.
For example, the "iso" in isogiku means "rocky shore," suggesting that this type of chrysanthemum (giku or kiku) is accustomed to the strong winds common along coastlines. Similarly, the "kawara" in kawara nadeshiko means "dry river bed," suggesting those plants have a degree of drought-tolerant hardiness.
Local charm: A delicate purple flower of the native kawara nadeshiko YOSHIAKI MIURA PHOTO
But not content to merely urge gardeners to pay more attention to native species, Sugii suggests they will find it more fun to choose plants that are "visibly Japanese" as well. By this it turns out she means plants whose forms consist of "lines," rather than "flat planes."
Tokusa (Equisetum hyemale), for example, which grow up to about 1 meter high, "consists of dead-straight, dark-green shafts, so they are reminiscent of a Japanese aesthetic," Sugii said. Still, she laughed off the suggestion that they look like a bonsai version of bamboo. "They're a totally different plant," she said.
Gardeners looking for a larger shrub might try a ookamenoki (Viburnum furcatum), which has similarly ramrod-straight branches juxtaposed nicely with generous round leaves.
"Another characteristic of Japanese plants is that they are not orderly like a conifer — the arrangement of their branches is often quite disordered," explained Sugii, confounding somewhat the stereotype of all things Japanese being nothing if not well ordered.
That trait, she explained, has fed into ikebana, the traditional art form in which the tasteful arrangement of varied cuttings is paramount.
Green seen: Akemi Sugii leads a tour atop Suntory Hall in Ark Hills. YOSHIAKI MIURA PHOTO
Still, Sugii thinks Japanese native plants have had a problematic relationship with the local form of flower arrangement.
Several decades ago there was a move to bring sanyaso (native mountain plants) into ikebana, she said. Plants such as shojo bakama (Heloniopsis orientalis) became popular for their tiny and delicate flowers, but as they were native to high altitudes, they soon became infamous for the difficulty of their cultivation.
"Because of this sanyaso movement, Japanese plants have a reputation for being difficult to raise in private gardens," said Sugii, who now sees it as her mission to "tell people that there is more to native plants than sanyaso."
Hence the native-species section at the Ark Hills rooftop garden.
However, if you make it there on Friday, April 24, or Saturday, April 25, (the gardens are open 10 a.m. till 1 p.m.), you might have to fight your way past crowds of people marveling at the rose beds.