Japanese Black Pine (Pinus Thunbergii) is considered to many as the most classic of bonsai. With its striking appearance of craggy bark and soft evergreen foliage, it’s hard to ignore the beauty of this tree which is native to Japan, Korea, & China. Below I have included a few guidelines to growing & caring for your Japanese Black Pine, however I would also like to note that I am writing this from a sub-tropical climate in Brisbane, Australia; and that some of this information maybe partially invalid to other bonsai enthusiasts around the world.
How to repot your Japanese
Black Pine?
Autumn (March-May) is the ideal time to repot Japanese Black Pine, although I have heard of others that have had good results repotting in spring (September-November). I prefer autumn as buds start to develop in spring & I don’t like the disturbance of this growth period. Make sure to rearrange the root system when transferring the tree & not to remove anymore than one third of the root ball at anyone time.
This should only be done to trees that are strong & healthy, & free from disease, every 2-5 years depending on the size of the tree. A good sign of health in Japanese Black Pine is mycorrhiza, an organism that lives in the root system of the tree & assists the roots in absorbing nutrients. Never bare-root this evergreen because you want to maintain this beneficial relationship between each repotting.
Further styling and refinement
Candle Pruning: Decandle Japanese Black Pine in spring to stimulate a second flush of growth in summer. This technique is to stimulate back budding, which causes stress to the tree and forces to activate dormant & adventitious buds on woody growth. This assists in buds to grow from within the trees interior, creating branch ramification. By practicing this you are encouraging the tree to stay compact in size, without it growing larger each year.
Needle Removal: Japanese Black Pine needles grow in pairs, & this means they must be removed as pairs always, at a certain time of year. When needles are removed from the pine the entire tree is placed under stress, so I recommend that this is done on healthy & vigorous trees only. Needle removal should only be carried out on Japanese Black Pine that have reached a certain level of refinement, as this technique would only weaken young trees. This is actually a quite extensive subject that I will cover in depth in the future.