Tip of the Week  #22

Dan, a professional arborist with North Country Tree Service, sent the following question.  It contains some technical terms & issues, which you don't need to understand to get information from the response.   His letter follows, then my response.

Hello, I am an arborist with 22 years of pruning and removal experience. I have visited your web site because it is very professional and interesting. I thank you for your dedication to bonsai and the art and science it involves. I do not own a bonsai at this point but was wondering if a bonsai is similar to the trees I prune on a regular basis. For instance:
1. Is 'tipping' and 'topping' of the tree considered mutilation like it is in my profession? You achieve undesirable results and damage roots when internodal cuts are made outside the branch collars or when proper techniques like crown reduction, drop crotching or crown raising are not utilized.
2. Do bonsai have branch bark ridges and swollen collars? And if you prune these parts incorrectly do you risk non-compartmentalized decay and splits?
3. When wiring your bonsai are you concerned about branch or trunk girdling or damage to the bark and cambium?
There are many other questions but if these three situations are parallel to my profession than I'll assume bonsai have the same tree biology as my 100' specimens I work in and that the same rules for inclusions, epicormic sprouting, micro and macro elements, mycorrhizae, pH, apical dominance meristems, phloem, xylem... all apply???
Do you think they do? I would appreciate your expertise and it would surely be of interest to me and my profession. Thank you again for devoting your knowledge to a beautiful living thing. Trees were here millions of years before man and they remain a privilege for us all.

Dan,
A tree has the same environmental range limitations in nature as it does when cultivated as a bonsai (a Japanese White Pine won't survive the warm Florida winters, a Serissa won't survive the cold Northern winter outdoors, a New Zealand Tea Tree won't survive if the soil is dry, etc.) From there, they would seem to part ways. There appear to be parameters for pruning full sized trees that I was unaware of, in the same way as you are unaware of corresponding aspects of bonsai cultivation. The reason is simple. While we are both dealing with trees, we are dealing with them from diametrically opposed angles. You deal with them in their "natural habitat." I deal with them "in captivity." The same rules do not apply in all cases, but do apply in many.

A naturally developed, centuries old bonsai can cost as much as a house, and like a house, can be valued at well below a hundred thousand dollars, or well above a million.

By employing "artificial" methods of growing a tree, we can create a nice, aged-looking bonsai for 1/10th of one percent of the cost of a corresponding "natural dwarf." In bonsai cultivation, "tipping & topping" are a necessary evil, which, when done properly, have minimal impact on the overall esthetics of the bonsai. As you know, a tree has a genetic maximum height, which, in nature, is reduced correspondingly by the amount of available soil, the quality of that soil, the amount of available nutrients, the amount of available water, daily exposure to sunlight, wind conditions, the climate, and other factors.

In bonsai cultivation, we can control the first five, but it would be impractical for someone like myself who lives in New York City to raise a tree near the timber line of a mountain in the Adirondacks to expose it to the severe winters. I can't change the prevailing winds to create a windswept style, or the climate, which affects the overall growth, and ratio of wood to foliage growth. These are things which we do with wire, scissors, and other tools and methods. Decay in cuts is controlled by the use of things like cut paste and lime sulfur. Splitting is not a problem because you don't have branch sections of a bonsai that weigh as much as a car, and cause stress on the tree's structure. We usually make cuts just above the node, then later, as new bark begins to form, the "stump" can be trimmed & shaved to give a natural appearance In some cases, we "jin" the branch. That is where the bark and foliage is stripped from the branch. Lime sulfur is applied to give the whitish gray "blanched-bone" appearance of natural dead wood on a tree, and preserve the wood.

As for wiring, it is very important to choose the proper gauge wire for the branch you're re-shaping, apply it so as not to dig into the bark and cambium layer, wire the branch in it's natural shape, then bend slowly into the desired shape little by little over weeks , months, or sometimes years to avoid scarring and damage. The wire should be removed and re-applied periodically to avoid damage to the branch. A Japanese Maple should be re-wired every two to three months, where a Japanese White Pine can go six months or more without attention. The duration depends on factors such as the species of tree, time of year, thickness of the branch, wire gauge, etc.

As for the biology of trees you mention in the second part of question #3, they all exist to some extent in bonsai cultivation. Mycorrhizae (a symbiotic soil fungi that attaches itself to the roots of most trees, which help the host plants absorb more water and nutrients while the roots provide food for the fungi) is essential in pines, so you should never wash all the old soil away when re-potting. It's not too important in Maples, which will eventually develop new growths of it, so all the old soil can be removed, and the roots washed clean when repotting.
Soil pH is very important to proper health and development of a bonsai. That's why we offer three different meters to measure it.
In general, you want everything that is available to a full sized tree to be available to a bonsai, you just want to control the amounts to control the growth rate.