Cultivating Syzygium as Bonsai

Syzygium buxifolium (Myrtaceae)
Syzygium is a genus of flowering plants, belonging to the myrtle family - Myrtaceae. The genus comprises about 500 species, and occurs in the tropical and subtropical regions of the Old World. Most species are evergreen. Several species are grown as ornamental plants for their attractive glossy foliage, and a few produce edible fruit. The most important species is the Clove Syzygium aromaticum, the unopened flower buds are an important spice.

Over the last 2-3 years one particular species - Syzygium buxifolium - has begun to make an appearance on the European bonsai scene. This species is native to the Hunan province in south-eastern China. The area is a transition zone between subtropical and temperate forests and is rich in bio-diversity. The areas weather is generally mild with an average temperature of around 17ºC. Winter temperatures average around 4ºC but can go as low as -12ºC.

My first meeting with syzygium happened when some Chinese offering pictures arrived in my mail box. Some very nice yamadori material….and the price was very good! Despite extensive Googling I was unable to find any cultural information on the species. However I ordered the trees and a few months later they arrived on a bitingly cold February morning.
My initial impression was delight. Despite 6 weeks at sea in a dark refrigerated container the trees looked stunning, resplendent in bright green stiff and shiny little leaves on red twigs. The deadwood areas of the trees were spectacular and the live veins running over and around the trees were exceptional. The foliage is similar to buxus as the name suggests but is much finer and emerges red on red twigging. Little clusters of insignificant white flowers appear in mid to late summer but don't hold your breath!

What follows is my own personal experience of keeping syzygium on the east coast of the U.K where I think our climate is a little more 'stable' and 'mild' than compared with some areas of the country.

In general the cultivation of syzygium can follow that of the native European Myrtle - myrtus communis. However there are significant variations primarily based around the fact that syzygium is not as strong or robust as the native variety. I think little and often is the pertinent phrase here.

If your tree has been recently imported there is a fair chance it is potted in red clay or river mud. Whilst the tree will survive in this soil it will not thrive in our climate. Before simply re-potting the tree it is important to asses it's health and condition and to ascertain the degree of root development. Some trees I have seen are only one season from collecting. If in doubt it is best to leave the root ball alone for the first year whilst the plant roots well.

When re-potting (always in spring) carefully crumble the soil away from the roots with your hands and wash away the residue with a hosepipe. Do not root prune at this stage. Remove dead roots and return everything else to the pot very carefully. Do not remove roots unless you are confident the tree can continue without them…if in doubt wait.
The best soil mix I have found for this species is a mix of clean sieved - pine bark - akadama or kanuma - kiryu or pumice in equal volumes. The species likes an open, warm and free draining soil that holds moisture but that is not wet. Given this the tree can fill a pot with healthy root over just one summer. Generally the tree responds badly to root disturbance. Make sure the plant is very well secured into the pot!

Syzygium has proven to be hardy in the U.K. Over last winter we experienced temperatures down to -8ºC. During that period I left some trees out unprotected. Some slight frost damage occurred to the very tips of unpruned previous seasons growth but this only ever amounted to 4 leaves on each shoot. Since that time the trees have grown well and with no long term adverse effects. Trees that were left outside under an open roof in good light and air circulation have done exceptionally well, in fact better than trees kept in a warm glass house.
Regarding ongoing care I find the species appreciates full sun in an open position, copious watering and fertilising and constant pruning. Pruning technique is the same as Chinese elm and the tree will bud from old wood readily. To date I have not experienced any pest problems.

The deadwood that invariably features heavily with these collected trees needs special care. It is important to clean all cavities within the tree of soil. The 'trunks' of syzygium seem to be formed underground and so they often have soil, stones and roots in strange places. When the wood has dried thoroughly treat with a clear wood preserver rather than lime sulphur. Do this at least twice each year in summer.

Wiring is a very pains-taking operation as the branches are brittle, the bark is very, very thin and the tertiary twigging is very delicate. Wire in summer using aluminium. When bending thicker branches try to use a twisting motion. Observe wired trees carefully, the branches thicken rapidly and wire will soon begin to pinch. New growth will turn up to the light and grow vertically.
In summary I would say that, putting aside prejudices, syzygium buxifolium has been a very rewarding species to cultivate as bonsai. It has a few unique foibles but overall is a very forgiving tree that develops quickly. The tree's form is very beautiful, it is fine and delicate with stunning colouration. I have seen some wonderful outrageous shapes and some strange styling ideas but….viewed as raw material I think the opportunity for creativity is exciting and besides it's nice to have something a little different to cultivate.

Graham Potter
© Kaizen Bonsai Ltd
07/08/2006