Training Black Pine for Bonsai

by Brent Walston

Introduction

I discourage beginners from working with Black Pine, Pinus thunbergii, because it takes so long, and you need to know so much just to begin. I started with Black Pine, ignorant of this fact and massacred a lot of plants learning how, even with John Naka's book, Bonsai Techniques I. I bought about 100 of them in one gallon cans, old root bound plants that appeared to have potential. Some of them have turned out to be really nice trees, but ten years, later the best are still several years away from being finished bonsai. Not a subject for the impatient. So when beginners ask me what to do with this seedling pine they just bought, I just roll my eyes and try to talk them into a nice deciduous tree.

Getting Started

Growing pre-trained material from seedlings has turned out to be even more difficult than styling and maintaining larger material. It is imperative to get that first whip to break buds, or already your first branch is a foot off the ground. Then there is also, in my opinion, the importance of getting some movement and taper to the trunk without losing all the low branches. It takes me about five years to get a good starter one gallon plant suitable for small bonsai or for growing on. This is about twice as long as deciduous material. Unlike deciduous plants, pines need to be developed from a very early age for a particular style and size. You need to have this image in your head. Of course larger nursery material can be used but the possibilities are always severely limited by the existing branches. To change this you must cut back most of the tree and grow a new top for the tree from an existing branch.

Aside from the styling aspects, which I will leave for later, the two rules for branch development are very simple, but the full ramification of these rules took me three years of experimentation to truly understand. These are Naka's rules for branch development:

Pruning Rule One: Remove All the Candles

Remove ALL the candles in spring that are longer than one inch. Can't get much simpler than that. I have added a corollary, remove even the one inch candle if it is a terminal bud unless you simply want a branch extension. Removing it will force side buds and a continuation of nice forked branches that are angled outward from the apex of the joint.

OK, what's spring? The whole timing issue is extremely important. The timing is exactly the reverse of what common sense would tell you. You should candle vigorous growth LATE and weak candles EARLY. Why? Because the whole point is to force secondary growth that will be smaller and tighter. This growth will become the branches that you will keep and the best branch forks are not pruned to the right length, they are GROWN to the right length so they end in a terminal bud as a site for next years growth. Candle too early and the secondary candles will have too much time to develop and become too long, none of it will be usable as the branch extension. The longer you wait to candle the shorter the secondary candles will be. Very long candles may be broken early in the season to keep them from extending fully, then removed entirely, later, when the timing is right for their removal.

This timing varies greatly with the climate in which you are growing. In warm climates with long seasons the candling should occur much later to ensure that the secondary candles don't have much time to get too long. I have a very long growing season here in Northern California, so I don't candle until the end of June or the beginning of July. Only experience will show you what is the right time. You just have to jump in and watch how long those secondary candles get. The vigor of the tree and the location of the branch on the tree will also affect the length of the candles and you have to factor that in too. Candle weak trees earlier to give them more time to push. Candle vigorous trees later to slow them down. Candle lower, weaker branches first, more vigorous top branches last.

Why not just whack candles or new branches that are too long? By removing the terminal bud on a new branch (candle) you will stimulate the adventitious buds at the base of the base of the new needles, this will result in coarse atypical growth since they won't occur in a whorl (node). If you have to do it to make an older branch break buds so be it, but it will take several years for this growth to take on normal characteristics. By growing branches the right length and leaving the terminal bud intact, the new growth the following season will be normal, that is, from the tip and the whorl of secondary buds at the base of the terminal bud. This will produce nice short fat little branches normal in every way.

Needle length as well as candle length is also affected by this procedure, and for the same reason. Most pines (and I see many of them) have needles that are too long. This is usually the result of removing candles too early, or removing only part of the candle instead of the whole thing. The needles at the base of a partially removed candle will be full length. Needles on a properly grown short secondary candle will not have sufficient time to grow full length and will be nice and short.

Rule Two: Reduce the Whorl of Secondary Candles to a Forked Branch

In fall, remove all the branches that formed from the whorl of SECONDARY candles except for two. This rule is much more straight forward and easier to understand than rule one. The two branches (that were candles) will form the next fork in the branch. Here you can choose which to keep according to your design parameters. Usually you will want the two that are in a horizontal plane, if they are the right length. The secondary candles will rarely all be the same size so you get some choice for the branch extension. You can keep the nice short ones if you are at the end of a proposed branch or longer ones if you are just beginning to develop a branch. Make sure they have a good angle between them and you will not be necessary to wire.

There is also another design aspect to be considered. You can choose candles of approximate equal length to form a sort of network of secondary branches, or you can choose a short one for the side branch and a longer one for the branch extension. This will give you a MAJOR or main branch with alternating short side branches (you must choose alternating short branches).

The timing is not quite as critical for this aspect of pruning. Give the tree the entire season to grow to strengthen it, but don't prune too late or there will be insufficient time to set new buds for spring in areas where you want options for changing your mind. I usually do this work in November. The other consideration is that the tree is very naked after fall pruning, and you can enjoy it longer by delaying it.

And finally

For more on how to prune and grow Japanese Black Pine see the companion article to this piece: Growing Black Pine for Bonsai