Janine Droste revisits the Mecca of satsuki bonsai
If you say Kanuma you at once think of satsuki. Satsuki, or Rhododendron indium, is one of the most popular bonsai varieties cultivated in Japan. Needless to say, it has become a specialty grown mainly in the area of Kanuma, a city just north of Tokyo. It is the principal place where Satsukis are grown and where, during May, the colourful flowers burst into life during the annual Kanuma Satsuki Festival
During spring last year, with my husband, Jan Droste, I travelled to Japan. Of course, a visit to Japan for us would not be complete without going to Kanuma. During our visit to this city, which is the epicentre of azaleas, we revisited the satsuki nursery Kobayashi Sangyo after a long time.
In 2005 I went to Japan with Mr Gerrit Lodder (bonsai importer in Harmelen), because at that time I was writing my first book on satsuki and wanted to learn more about this fascinating variety. I got in touch with Ryuji Kobayashi and his son Hiroharu, and they were very willing to help by providing me with all kinds of information on the satsuki.
More than 40 years
Their nursery was established in 1965. Many of the old satsuki bonsai were created by Ryuji himself. The company mainly focusses on satsuki, but have many other varieties as well and produce all kinds of bonsai soils, such as Akadama and Kanuma tsuichi.
I was really overwhelmed by their collection of trees. One satsuki after another, each ever more beautiful and bigger than the other.
Although we visited many other satsuki nurseries, Kobayashi Sangyo was by far the most impressive with the best trees.
Since that time I have always kept in touch with Hiroharu.
In 2016 Hiroharu and his colleague Hideo Sekiyama, the Satsuki specialist who has already given various workshops in Europe, visited my Satsuki garden in Kessel-Lo, Belgium. Together they worked on several trees in my collection.
“Kanuma is the epicentre of satsuki“
Mainly for azaleas
The fine nursery of Ruyuji Kobayashi and his son Hiroharu is located in the town of Kanuma, which is also known for its soil, Kanuma tsuichi. It is a granular Japanese potting medium used for ericaceous, (acid loving) bonsai. It is found a few miles out of the town. The soil is dug out from 10 feet down, allowed to dry, crushed and then sorted according to the size of the grain. This is done right here at the factory of Kobayashi. Kanuma is more acidic than Akadama and therefore, used mainly for Azaleas, Camellias, Gardenias and other acid loving varieties.
Kanuma facilitates fine hair root growth. It retains moisture and can absorb more water than its weight and yet allows for air space. Its pH will vary from 4.5 to 5. Both Kanuma and Akadama simplify the repotting chores since roots are fibrous rather than hard.
Hiroharu gave us a tour round the nursery together with Hideo. It’s a huge place that consists of several greenhouses. Hiroharu showed me how satsuki are grown; it all starts with cuttings placed in polystyrene boxes, filled with fine Kanuma soil. As well as the one-day-old cuttings, there was a plot for 3 -week-old cuttings and a tray containing 1-month-old cuttings, which already showed a fair number of roots.
The warm greenhouse
In another greenhouse you could see the satsuki that have been taken out of the field. This took place during the winter months and their roots have been sprayed clean. Some are planted in large wooden boxes, others in large plastic containers. These trees are kept inside the warm greenhouse during the winter months at a temperature of 10 ° C, or warmer, to stimulate growth and so they don’t go into dormancy. Elsewhere there are cuttings of about 2 years supported by a stick and 3-year-old material.
Many satsuki are grown only for their flowers, not for bonsai aesthetics, so a slim long trunk shape is ideal to show off the flowers. Not all satsuki, however, live this luxury life. Many are grown in the open field in a mixture of ordinary soil with 20% acidic rhododendron soil. There are 5,000 satsuki of various sizes. When cultivating satsuki in the open field the emphasis is usually on thickening the trunk using so-called long sacrifice branches and developing a basic branch structure. Hiroharu focuses on developing fine branches later.
At the nursery you will find not only finished, impressive large satsuki, but also smaller satsuki and so-called starter material available in all sizes.
As well as the nursery there is a private collection; here the most beautiful satsuki are found. I could not resist taking a look and before I knew it we were face to face with giant satsuki of incredible quality, maturity — and very old. Impressive! The number of masterpiece satsuki here is amazing.
The largest trees have a diameter of almost one meter. With such thicknesses you expect heavy scars, however, thanks to the fine craftsmanship of the satsuki specialist these were invisible. Seeing the whole process from cutting to mature satsuki bonsai is most interesting and a real eye opener.