For all the content out there about bonsai, we continue to have limited access to information about root work. Let’s call it poetic irony that the unseen content aligns with the unseen part of our trees.
When we select a plant for bonsai, the roots are the one area we (usually) can’t inspect. Sure, we can check out the ever important nebari. Some of us have even been known to dig down into nursery pots with our bare hands to try to find the root base, but what can we really know about the root structure before we actually have the plant out of the pot and start working into the root mass?
Here’s a fir that I knew needed some root work when I got it. Visible above the soil surface was a root circling the trunk. This tree came into my care a year ago and I let it grow for a year so I could make sure it was strong and healthy before repotting and tackling that problem.
What the heck is going on with these roots?
To my surprise, when I got it out of the pot and pulled away some soil the situation was something different entirely from what I was expecting. Far worse than a long, runaway, circling root, what I found was a very thick root that emerged from the trunk well below the soil level, travelled UP along the trunk, split in two like a T, and then each bar of the T wrapped around the trunk in opposite directions.
Luckily, and perhaps partially because of this bizarre structure, there was a somewhat bulbous trunk flare below where the T root was strangling the trunk. this is the start of the tree’s new base.
The whole T root had to come off, and I am fairly confident the tree will recover well. It should be MUCH better off with this root removed, and it should turn its root growing energy to the much smaller radial roots that now sit just below the soil surface.
Problem root removed and replanted.
The cut is visible in the photo above at soil level on the left side of the trunk. Just to make sure you can appreciate how weird this was, I have drawn an orange line in the photo below to show where the root had been before it was removed.
Orange line shows where the root had been.
This tree is on its way to a much brighter future. With a little time the remaining roots will develop into a mature root mass that is much better organized and better looking.
Let’s do some science – a very straight forward experiment. All other things being equal, what difference do a few weeks make in terms of when you choose to prune spring growth?
Bonsai teachings say we wait to prune new growth until the spring leaves are hardened off. This is a gray area at best for most species, so what is it that we are really waiting for? Or put another way, what does hardening off signal that makes this a good time to prune? Ryan Neil speaks in terms of the tree being energy positive, having regained the resources spent through the winter and the spring flush. If waiting to prune allows the tree to build energy, might waiting longer result in more energy stores that can be measured in stronger growth the following year?
The subject of the experiment will be two boxwood trees, genetically identical, very near the same size and planted in pots with similar dimensions. Growth on these boxwood clones was very consistent and well balanced in spring of 2021 with most spring extensions having 6 leaves. In the year leading up to this baseline, the two trees were treated in a similar fashion including the timing of spring pruning for both plants done within a three day window in May 2020.
In 2021 I applied the same pruning approach to both trees — most spring shoots were reduced to the first pair of leaves, some older leaves were plucked to allow more light and air into the foliage pads, and relatively few other branches were reduced or pruned to improve the structure. The only difference is that they were pruned 5 weeks apart — the twin trunk was pruned on May 16 and the single trunk on June 19.
Will the extra time with hardened leaves provide any notable benefit?
Before pruning May 16, 2021After pruning May 16, 2021Before pruning on June 19, 2021After pruning June 19, 2021
Over the year that followed these trees were treated consistently – water, fertilizer, exposure, winter placement, everything. Both trees are healthy and have shown no signs of pests or disease. As mentioned above, these are genetically identical. In fact, the two trees were split apart at the base from one plant over 15 years ago. Relative to my other bonsai experiments, this all adds up to some pretty strong controls.
June 11, 2022 with no pruning since 2021.
Both trees pushed reliably in 2022. I let them both harden off with no miscellaneous pruning. Now it’s just a matter of measuring this year’s growth. What do you guess the results will show?
I randomly selected a couple dozen shoots to examine on each tree and counted the new leaves. The current year’s leaves are still quite easy to distinguish from last year’s growth which is a much darker green.
The twin trunk tree had 8 leaves per spring shoot.
The twin trunk tree, the one that was pruned earlier in 2021, had eight leaves on the vast majority of new shoots with just a few having ten.
The single trunk tree had 6 leaves per spring shoot.
Almost every shoot on the single trunk tree, the one pruned later, had six leaves with just a few having eight leaves.
This is not what I expected! My hypothesis had been that more time before pruning would result in more stored energy leading to stronger spring growth. I would not have been surprised with no apparent differences, but instead I got the opposite result!
Obviously, there are differences to acknowledge which could explain the measured difference. The pots are both shallow rectangles, but they are not identical. The single trunk vs double trunk makes for easy visual distinction of the subjects, but more relevant is the exact amount of foliage on each tree. I estimate that the twin trunk example carries 20% more foliage just as a factor of its design. Whatever the differences, I am reminded that I had nearer equal growth in spring of 2021.
What could this mean? There are two possibilities that seem most likely:
The differences between the trees are enough to result in the difference in spring growth and the time of pruning was not a significant factor.
Pruning earlier positively contributes to the strength of next year’s flush by allowing the tree more time to build energy into the buds being set for the following spring.
Let’s consider that second possibility with a comparison to the second flush on decandled black pines. We know that JBPs decandled earlier have more time to grow a second flush before the end of the growing season resulting in stronger growth and longer needles on the second flush. JBPs decandled later will have smaller, shorter growth in comparison. Pine growers use this knowledge to time the pruning of trees based on size (larger trees earlier and smaller trees later) or to help balance growth on a single tree by decandling in carefully timed phases.
The boxwoods in our experiment didn’t push a second flush (though boxwoods sometimes can), but could it be that the timing of pruning impacted how much energy was stored in the buds being set for the next year? If bud development is happening between mid May and mid June, could it be that the twin trunk tree was able to store more energy in just two buds per growing tip (at the base of the two new leaves left on the shoot) while the single trunk tree was expending energy to build six buds per tip? …only to have four of those six removed a few weeks later?
This is only a theory, but I am inspired to continue making careful notes about the timing of pruning on these trees as well as other specimens and species in my collection.
I collected this holly a few years ago. Did some hard root pruning in spring 2020 to get it into this pot, and have let it grow wild since then. Read about the work from last year here. As you can see, it is big and hairy and needs a trim.
Big holly before styling, June 2021
Don’t be fooled by this front view though. The crown is coming toward you, and back branches need to be positioned and developed to catch up. Here’s a view from the side so you can see what I mean.
View from the side to show how undeveloped the back of the tree is.
This holly has proven to be extremely vigorous, and after this styling I will have to keep on top of it to develop finer branching. I am confident in its ability to back bud and fill in, though. In fact, the first thing I need to do is remove several suckers growing from the base of the trunk.
Removing suckers that will grow all around the base.
The next step is to analyze the structure and remove whole branches that don’t serve the future of the tree. I remove branches that are too thick, in a poor location, pointing the wrong direction, or conflicting with a better branch in the same area. The goal is to leave a better primary structure to build off of. In the image below you can see where several branches have been cut.
Holly showing where several branches have been removed.
The remaining branches were far too long. I shortened them by selecting cuts that would leave a better taper as the branch moved away from the trunk.
A few guy wires were applied to pull primary branches down into position, and a nice shape for the silhouette was my goal for the final length adjustments.
Do you name your bonsai? I don’t necessarily “give my trees names” as such. In my notes I often give descriptive names to individual specimens especially when I have multiple trees of the same species, but those are usually names like “concord” for a tree I found on Concord Drive, or “monster” for that particularly large tree. The closest thing I come to giving a proper name is when I refer to a tree by the person I got it from, such as “Acer palmatum, Sandi” for the Japanese maple that I got from Sandi’s collection.
I purchased this Satsuki azalea from a local grower last summer. There seems to be a bit of uncertainty regarding the cultivar. Is it Row Koku or Kow Koku?
A better title for this post might be, “I Hope These Steps are Moving my American Beech into Refinement,” but that is a few too many words.
Most available literature on beech bonsai addresses European beech, Fagus sylvatica, but I have been experimenting with its larger-leafed cousin, Fagus grandifolia, to see what bonsai methods are effective for this American native species.
Boxwood is one of my favorite species to work on. The work is precise, detail oriented, and rewarding… if you are patient.
The work I’m doing today should be done only after the current year’s growth has had time to harden off. My preferred way to determine whether boxwood leaves have hardened off is by feel, but that’s hard to show in a blog post. Slightly easier to show is the color, another indicator of hardening.
Boxwood branch showing tender new growth and older, darker colored leavesContinue reading →
Bonsai is an art of patience. Sometime around four years ago I found a Japanese holly growing wild in area where I knew I was able to collect. It was overgrown, but I saw potential for not just one, but at least two trees. I waited until the following growing season to take an air layer (which you can read about here), and then until the spring after that to dig the parent plant (which you can read about here). It has been recovering in a planting box for the last couple of years, so we are four years in and we aren’t even to the fun part yet!
Have you ever taken a bonsai to a club meeting or a workshop just to get everyone’s unsolicited advice about how you should style it? We have an often repeated joke in our local club that if you ask ten different people you’ll get twelve different answers. That’s especially true when you have an unkempt tree that is in desperate need of styling. And apparently also true if you don’t even ask.
Bonsai Iterate 