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.
As I have worked on my ficus bonsai this summer, I have been considering a question. Who do we learn from? For a number of years I felt pretty good about learning about how to care for tropicals from folks who have lots of experience, but those experienced folks I’ve been learning from are bonsai practitioners who live in subtropical areas like Florida.
Ficus microcarpa before work, summer 2021
The approach I have been following for a number of years has been to do heavy work on ficus mid-summer including defoliating for easy wiring and styling, and I repot then as well when necessary.
I really started questioning these practices when I listened to a recent podcast from Bonsai Mirai. The Asymmetry interview with David Cutchin addressed how some of the habits of Florida bonsai practitioners may not be such a great thing for their trees even in Florida where tropical species are suited to the climate. Specifically, the regular practice of defoliating was called out.
Extra problematic, then, is those of us who live in more Northerly locations learning from and copying those practices that seem to work well in Florida.
Ficus microcarpa after defoliation, summer 2021
I am in Northern Virginia, and for my tropical trees mid-summer is when they have just started to show renewed vigor after recovering from six months inside. Cutchin suggests that regular defoliation is really hard on the continuing vigor of the trees. If that’s true in Florida, the lost vigor is especially worrisome to me when the trees can only enjoy being outside half the year and struggle to maintain vigor anyway.
The range of leaf sizes removed from the tree when defoliating.
Nevertheless, I wonder if and suspect that applying this technique might help to balance energy in the tree. The image above shows the significant range of leaf size that was cut from the tree during its recent defoliation. These range from a half inch to three inches. But if I suspect encouraging a full set of new leaves might help to balance the growth of the tree might some pruning or just a partial defoliation possibly do the same?
Just a bit of wire and pruned, after work summer 2021
One way or another, it’s a bit late for this specimen, but I decided to try different approaches with some of my other tropicals. A couple trees that have been defoliated annually for the last few years have just been pruned without defoliation this year to see if it makes a difference in the vigor and growth of the trees. The experiment is not very scientific since tree growth varies from year to year, but if all I am doing by defoliating is slowing down the growth and development of my bonsai, I am all for trying something different.
Ficus microcarpa two weeks after defoliation.
In the meantime I will enjoy watching this tree fill back in with a brand new set of leaves.
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.
Satsuki azaleas are named for when they bloom. They are known for blooming in May, the fifth month. Satsuki means “fifth.”
Azalea before work begins
This azalea decided not to bloom until June. And the blooms you see represent only about 50% of the flower buds. The others hadn’t opened yet when I decided to start work on this tree anyway. The first step was to remove all of the flowers and unopened flower buds.
Removed flowers at various stages of bloom
Once that was done the biggest task was to prune down to just two lateral branches of the whorl of branches (often 5) that grow from the base of each flower. It seemed easiest to show you this in a video. Check it out at on YouTube.
Azalea after pruning
A little wire seemed in order as well, and we are done for this season. I will let the tree grow and set buds for next year, and at most I will remove unwanted suckers or branches growing in the wrong direction.
This tree is just in its third season since initial styling and I’m happy with how it is progressing.
This privet was a landscape plant on my property until I removed it from the garden in 2015. Since then I have gradually selected from and reduced nine trunks to three, and reduced the root system to fit in an appropriately sized pot — if not a refined looking one.
Vicary privet, March 2021
Allowed to grow freely for most of last season, this (above) is how it looked in early March, still holing last year’s leaves. The dark green and sometimes purple cast of the leaves is it’s winter color. In spring the leaves are a bright yellow-green which is why I suspect this is a Vicary golden privet, Ligustrum x vicaryi.
Purple color of winter leaves.
The first step of many this spring was to remove the old leaves.
Leave removed.
With leaves removed, I could see what I was working with and apply wire without interference. I wired out most of the branches and set them into a rough placement before repotting.
After building strength last season, dense roots had slowed percolation, so a bit of root pruning and some fresh soil — two parts akadama to one part lava rock and one part pumice — set it up for continued growth and vigor. For now, it is back into the same unrefined pot until I can find or make a better one.
Roughly wired and roots pruned, ready to go back in a pot with fresh soil.
Once secured in the pot, I refined the branch placement a bit and used a couple of guy wires to set the design.
Repotted and wired, March 2021
Spring growth pushed shortly after, and below is what it looked like by the beginning of May. (Don’t mind the pink ribbon. This is just something I use to mark those trees that should be protected from frost if cold temperatures are forecast. I mark all trees that have been repotted this way until the chance of freezing temperatures has passed.)
Spring growth by early May
Many shoots had extended to 8 or 10 leaves marking a good time for spring pruning. Some were even developing flower buds, but flowers are not important for the tree at this developmental stage, so they were removed with pruning.
Flower buds developing at the tips of spring growth
I reduced strong shoots to just 2 or three leaves, and left weak shoots or branches that need to grow out or thicken (like the bottom branch on the left) with more.
I plan to stay on top of the growth, moving forward, to promote ramification and continue to fill in parts of the silhouette that need it.
That was a lot of work on one tree in just a couple of months, but it is on track to continue developing into a nice bonsai.
Once upon a time, on an very warm and pleasant December day, three Bonsai went to the bench for a winter cleaning. All three were Autumn Olive (Elaeagnusumbellata). There was a big, thick Elaeagnus; a medium, curvy Elaeagnus; and a tiny, shohin Elaeagnus.
Mama bear before pruning (Elaeagnus umbellata, 2020)
The three bears had been allowed to grow out for the last months of the growing season so each had long branches to be trimmed before hibernating for the winter. Despite being so late in the season, none of them had dropped all of their leaves. But this is normal for autumn olive in Northern Virginia. The oldest, inner leaves had fallen away, and a gradation of leaves from green to yellow-brown still clung to the newest growth on the outer branches. This is how I knew the time for a winter pruning was just right… not to early… and not too late.
A range of leaf colors which had not fallen.
Because the remaining leaves were at the end of the newest growth, there was no need to cut the leaves away individually. Pruning to two or three buds at the base of the new growth removed the remaining leaves, and setup the tree for spring growth that will improve ramification.
Mama Bear after pruning. (Elaeagnus umbellata, 2020)Papa bear before pruning. (Elaeagnus umbellata, 2020)Papa bear after pruning. (Elaeagnus umbellata, 2020)
The largest tree still needs the upper trunk line to thicken and improve the taper and transition from lower to upper trunk. To help this process along, I left one long sacrifice branch that I will allow to grow freely next season, even as I begin to refine the lower branching.
Baby bear after a hedge clip but before selective pruning. (Elaeagnus umbellata, 2020)Baby bear after pruning. (Elaeagnus umbellata, 2020)
All of the three bears need wire, but I will wait until late winter or early spring to apply it. For now, I will dress the cuts with cut paste and let them rest. Here’s hoping they will continue to develop, and live happily ever after.
This white pine, Pinus parviflora, came into my care last fall. It was a decade overdue for a repot, and as I discovered this spring, had a number of dead branch tips. Below are a before and after shot from removing those dead tips, and you can watch this short video talking more about this tree.
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?
The actions taken in the initial styling of an azalea combine to make one of the more horrifying acts of the bonsai art form. Horrifying to others, that is. I know this approach works, and it doesn’t bother me a bit! Here’s whatI mean…
Bonsai Iterate 