The Definitive Japanese Black Pine Guide

Welcome back to another Hakuju-En blog. For this autumn edition I would like to discuss Japanese Black Pine/Kuromatsu/Pinus thumbergii and the techniques used to establish a few key aspects of a quality pine bonsai. The method outlined in this blog is the Kimura method and was taught to me by both Taiga and Nobuichi Urushibata.

When defining qualities in Japanese Black Pine (JBP) bonsai, what are we, as practitioners trying to achieve?

To achieve the most proportionate bonsai, one of the first things we tend to discuss about any particularly great JBP is the needle length, which can be greatly reduced through a series of proper techniques. Another equally important aspect would the homogeneity of said length of needles, and the series of techniques, which are intertwined with the length.

Other important qualities would be ramification, branch length, movement, and coverage. These aspects need to be considered from the onset of developing a JBP; however, controlling them later on seems to be a delicate art unto itself, and we will cover these points as we go along.

So how do we manage to get the pine to grow shorter, more homogeneous needles? Firstly, we want to ensure our new pine is in excellent health, with no fungus or mite issues. 

Then it all comes down to timing, technique and thoughtful application of fertiliser. We will start this journey in spring (or when ever you acquire your new pine). We start by needle plucking; this is the most important aspect for homogeneity of growth. We pluck the old needles up the branch right up until we hit the last row of needles. In each sheet there are two needles, and in each row there are five sheaths, and the subsequent row under is slightly adjacent, which means the needles create a noticeable spiral pattern down the branch. We want to leave the top row, five sheaths; 10 needles. And a single black rocket shaped bud in the centre. If you notice there are more than one bud, remove all but the centre one. It is crucial you do this to the entire tree, sparing no bud. 

The next part is a very careful and thoughtful planning and executing of fertilising. It is well known and documented that nitrogen will dissolve in water, and thus, wash from your soil in around 4–6 weeks. Therefore, every four weeks, we need to fertilise with organic liquid fertiliser, with a rather high nitrogen NPK. Ideal NPK for pines would be 12/1/5. I use Seasol Power Feed (12/1.4/7) and I apply every four weeks leading up to summer. The last application will be in November, ideally around the 15th

During this time you don’t want to touch your tree. Leave it; don’t touch! Until D-Day (D for decandling–the practice of cutting every bit of new growth from the tree). The first weekend of December In Melbourne is perfect for decandling. Japanese Black Pine have evolved over millions of years in the southern part of Japan, where in summer Typhoon season hits, with extreme wind and rain. These storms often break trees down, and along with them, strip nearly all of the new growth from the tree. So the JBP have developed a second flush of growth in their genome to combat this. It’s not really understood why the trees produce more growth than before; however, we will take it! Summary: New growth is removed, second flush of growth is multiples of the first growth.

So let’s cover the technique in detail: each bud that was left untouched in Spring will now be a tall candle looking growth, and the needles, at this point, will be open, but the stem still grow, yellowing off slightly. There should only be one from each branch end and they will be delicate. Cut them off. Cut all of them–the big ones, the small ones, the ones that didn’t even grow, even those tiny little ones (Taiga called these “sleeping buds”).

Double check your needle count at this point. We want to make sure every bud has exactly the same number of needles; this will ensure each one will grow consistently. Now it’s time to sit back, water and enjoy the magic as, over summer, the second flush will emerge, small, rigid and plentiful. You’ll notice they will be a lot smaller than the first flush, but why?

Remember how you fertilised all spring and then stopped? Well, that whole time the tree was storing those nutrients up and then using them to grow the first flush. But we cut them off. Now, the surplus store of nutrients is running low, and the tree now has nearly three times the amount of buds to grow, maybe more! Not only that, but you made sure that each bud had the same amount of needles, so the nutrients are distributed evenly. Summary: more buds and fewer nutrients means less food for each bud. Everything is smaller, but don’t worry–we will fertilise again next year.

But why do the needles tell the plant how to distribute the nutrients? I hear you ask. Well, the needles are the photosynthetic material of the plant, and if each bud is producing the same amount of sugars from photosynthesis then the tree will consider each one as important as the next. 

Autumn arrives and you start wearing pants and a jumper, perfect! Let’s get into the fun part of pines–the dressing and preparing for the next wave. At each cut site, you will have watched one, two, three, four, or even five buds appear to replace the previous bud. It’s now time to select two to carry on to next year. This is a multilayered intelligent move. Firstly, it’s now cold, so the tree won’t do any reactive growing once you cut; no sun equals no growth. Secondly, the growth has stopped, so now that to reduce the foliage to two buds, it won’t effect the needle size.

So which ones do we select? Well we have a checklist for this:

1. Same size
2. Small crotch
3. Horizontally emerging

When we select the buds we want to make sure that the strength of each bud is the same. Pines want to be strongest at the top, because that’s where the most light is. We need to help the buds low down, or closer to the trunk, which may not get as much light as the rest of the tree. Buds closer to the trunk are really important to grow a new branch from when the current one gets too long (30 years down the track).

Some of the buds will be growing out of the cut site directly opposite each other, and others will be right next to each other. The ones that form the most acute crotch are the most desirable. 

Finally, buds facing either straight up or straight down are going to be problematic in the future, so ideally horizontal buds are selected.

At this point, you are free to wire and style the tree as desired. Everything is set in place and ready to go. If you do choose to wire, be careful not to snap any of the needles. Last year’s needles may be cut down to allow light into this year’s buds (aesthetically this is appealing too).

As winter sets in, it’s time to start planning your fertiliser program again. We would Ideally like to start fertilising in August and finish in November, bringing us full circle.