A Case Study for Applying the Water and Sugar Equations - Repotting the Risky Rose

Source material: 3/19/2021

            Hola bonsai amigos! Today is a great day because not only does your friendly neighborhood microbiologist (me!) receive his second Covid vaccine dose, but my immunized arms also come bearing another present to the bonsai community. As spring continues to march on, so too does the blog's coverage of my giant rosebush bonsai - this time the rose's latest repot reveals two fundamental equations of life to consider when manipulating bonsai or any plant.

            The "Risky Rose" was the second major repot I did this year; returning readers will recall from last week's post that this operation involved another of the largest trees in my collection - a yardadori/landscape origin rosebush turned bonsai. As discussed in the previous post, now that the tree has recovered several years after its initial transplanting endured a cross-country move and survived its first Ohio winter, our rose has definitely earned renewed attention this year. For now, I'm calling it the "Risky Rose" because it needed severe root reduction in order to change its planting angle and lift the upper half of the trunk out of the pot. Read on to understand the motivations behind this bold action, including what steps were taken to ensure this radical root reduction could be done safely.

            As with my last repotting post, "Repotting The Monster Mulberry - Revisiting the Basics", this repot was done with the help of my friend in the Columbus Bonsai Society, Kevin. Thanks, Kevin!

Sections

1. History of the Risky Rose (Last post)
2. Current Repot Operation
   2A. Repotting in Action
   2B. The Water Equation
   2C. The Sugar Equation
   2D. Applying the Water and Sugar Equations
3.  Blog Announcements

Here you can see a teaser of the rose's chunky trunk in its new position after its 2021 repot.

1. History of the Risky Rose

            As this post is already a long one, I won't rehash the details on the history of this tree. If you want those details, go read last week's post "Origins of the Risky Rose & Steps for Transplant Recovery". Here I will only reiterate the tree's starting point. We initially had very few fine roots and I was concerned for its survival. This temporarily limited our style choices... The health of the trees always comes before styling considerations, but with time and patience, we can move our tree towards the ideal we hope for them.

The Risky Rose's condition, as first found in February 2018.

2. Current Operation on the Risky Rose

2A. Repotting in Action

        As mentioned at the end of last week's post, our Risky Rose grew moderately while adjusting to its life as a prebonsai. Given its good health and multiple years of transplant recovery in a pumice soil mix, the tree may now finally have enough fine roots for me to place the tree closer to the planting angle I envisioned 3 years ago. Evaluating this possibility involved first uprooting and bare-rooting the tree so I could see the current situation of the roots and our likelihood of success. I'll let the pictures tell the story from here.

Risky Rose pre-repot. March 2021. The buds were swelling but not yet opened a the time.

Opposite view of the Risky Rose pre-repot, 2021.

The magnitude of the trunk on full display. Kevin for scale.

We had to prop the tree up with a board so the old soil would fall away more easily.

The rootball starts to show as the soil is removed. You can see there are many more fine roots than when I first found the tree! Progress. We love to see it.

Another view of the fine roots. In this picture and above, you can see the fine roots are over the full length of the trunk.

            During the course of the repot, I did remember vaguely my desire to raise the trunk to a new angle. In hindsight, Kevin & I arrived on roughly the same final planting angle as I proposed in the pictures I took way back in 2018. Unfortunately, at the time of repotting, I did not think to take an overhead picture of the fine roots to show the current root status of the critical lower end of the trunk. However, while testing planting angles once again, it was clear to me that while a substantial amount of roots would have to be removed to achieve the new angle, it was also true that the lower roots had made dramatic progress and should now be able to support the tree. As my bonsai teacher Dan Robinson would always tell me during repotting season - "It's not about how many roots you take off, it's about how many roots you leave behind."

            Despite the progress of the lower roots, our Risky Rose is still not placed at its final planting position. Part of the lower trunk is remains buried, one long root coming from higher up on the trunk was allowed to stay feeding the tree, and structurally the lower nebari is not ready to support the full weight of the tree - braces had to be added for now. These steps allow for the planting angle transition while saving as many roots as possible to reduce risk. Shifting the burden of water intake to those remaining lower roots is a step in the right direction and will allow us to take further action towards our goal in a few more years after the tree concentrates its root growth in the area we have selected for it.

Here you can see our final planting angle and one of the temporary wooden struts. Kevin helped me place it against the existing nebari to help hold the tree in place while the lower rootball improves its structural stability.

In addition to the one wooden brace placed directly against part of the buried trunk/nebari, the excess area of the pot was walled off. This was done because the limited lower roots would not find themselves easily able to use (dry out) the whole volume of the soil at first. If the soil remains too wet as opposed to drying out in between watering, then root growth and overall health will be depressed. It's the same idea which tells us not to put a 1-year seedling straight into a giant 10-gallon nursery pot and instead gradually increase training pot size. As the lower roots grow, perhaps this brace will be removed in the future to give them more space.

2B. The Water Equation

            If you've ever seen a tree that has half uprooted itself in a forest yet continued to live, you have seen firsthand evidence that trees often have unnecessary redundancy in a healthy root system. That is to say, trees and plants make more roots than they typically need because it offers security through more avenues to import water in times of drought. Given that the Risky Rose's root mass was reduced by about half or more in this operation, we may be fine if we only cut through redundant roots, but just to be safe, I thought back to the "Water Equation" I first outlined in my musings on the Mulberry repot post. There's no way to tell for sure if we removed too much, but we can guesstimate the effects of our actions and try to take counterbalancing steps in cases we deem it necessary. Let's first refine our understanding of what the Water Equation is in its totality.

The Water Equation:

The Water Equation is my own personal way of thinking about one of several conditions which any plant must always meet in order to survive. Let's break it down a bit further.

            If the Water Equation is not met for a short time, leaves on the tree may dry up and fall off. For a longer period, branches may be lost. And for an especially extended period, the entire plant would be at risk of dying. Any plant is constantly taking in or losing water - even in winter.

Water Intake:

Water intake in a plant can be broken down by its two main sources.

            For most plants, root import of water is the primary or only source of water intake. However, I've also heard it said in one of my college biology classes that giant sequoia and coastal redwoods have a unique ability to condense water from the high elevations of their uppermost branches. This adaptation would definitely explain how they grow taller than any other recorded tree species. Dan Robinson also has a hypothesis (he may have mentioned he got it from Walter Pall) that Ponderosa pines appreciate foliar watering because their large stomata could naturally use a similar process to take advantage of mountain dew in their otherwise arid native range.

Water Loss:

There are 3 main sources for water loss.

            Working conversely to water intake, water loss is primarily driven by evaporation from foliage (lumping in buds and branches here). Those who remember their biology classes will recall, plants have stomata on leaves and needles which can be opened or slowed to slow water loss during photosynthesis. Some species, especially succulents, also make thick waxy coatings on leaves to further slow water loss.
            With regards to wound evaporation, I'm mostly referring to large wounds that have not healed over. Trees also have mechanisms that impact this issue though such as compartmentalization and callouses to limit the damage and water loss from wounds.

            Lastly, with regards to new shoot elongation, the creation of new shoots, leaves, and other locations where the volume of wood is increasing all require water for these processes to happen. Any volume of plant material that is growing will be full of water-filled cells that are dividing while growth is occurring. Even for the plant vascular system, where new cells become empty vessels for water to move through the plant, water is initially required to create and maintain (fill) the system nonetheless.

2C. The Sugar Equation

            The Sugar Equation is the second model I've developed for thinking about the basic survival of plants. Here sugar is a euphemism for all sorts of energy because all energy starts as sugar for plants. Similar to water, keep in mind, the sugar equation's components fluctuate with the season. A maple capable of producing sugar today suddenly finds itself with no energy income in the winter. Then in spring again the plant invests stored sugars into new leaves so it can generate additional energy for growth once again. Sugars also move throughout plants - from the factories in the leaves, up to new buds, down to growing roots, and everything in between. On the whole, it is always true that a plant cannot spend more sugars than it creates.

The second fundamental equation of plant mathematics. I won't break down these individual components like I did for Water because sugar is much simpler. Sugar income comes only from one source - photosynthesis. Sugar expenses on the other hand come from literally everything else that plants do.

2D. Applying the Water and Sugar Equations

            Without thinking about it, our pruning and control techniques in bonsai regularly influence these equations. When we prune branches and reduce roots in moderation, the impact is not severe and we can do so without thinking. However, radical trunk chops, for example, rely on stored sugars to make new buds. Likewise, repotting in early spring relies on the fact that the trees aren't spending much water yet and have time to repair roots before water expenditures grow.

            In the case of the Risky Rose, given that our water intake has been significantly reduced, I also chose to prune some unneeded branching to reduce the demand for water. In doing so, I did remove some photosynthetic capability of the tree and stored sugars (buds) and therefore impacted the Sugar Equation and Water Equation at the same time. The sugars from the removed branches could be put to use in repairing roots, however, healthy plants have a supply of stored energy for such occasions. Judging the water loss to be a greater concern than the energy loss at this time for this tree, that is why I removed some foliage. It should be noted that under less extreme repot conditions, it isn't normally necessary to perform this counteraction.

Post-repot after some branch reduction (the ones with old leaves clinging on in the first 2021 photo)

            In addition to about a foot of unnecessary fine branching I removed (it wouldn't fit in the car anyway...), at some point after bringing the tree back from Kevin's I was possessed/motivated to remove some larger straight branching. See if you can spot the differences between the above picture and the below picture. I had been meaning to shorten some of these thick branches anyways. Too many taperless, straight sections make for a boring design! Pruning forces new buds that will change the direction of the branch! It's a long-term plan. Adding to my confidence when pruning back these select thick branches, last summer I experimented with pruning a few of the several big branches and observed roses have a great capacity for backbudding.

If you look closely, you can see the main branches that were reduced are midway on the uppermost trunk and some from the lower clump of branches too.

            While we've taken a dramatic step towards my final vision, I must watch our Risky Rose closely this spring and summer to make sure it can support itself on the remaining roots. With appropriate aftercare steps such as positioning it in a shady part of the garden, adding moss to the top of the soil, and closely monitoring its water levels, so far I'm happy to report the Risky Rose has leafed out in perfect health for the past month and is now booming with more backbuds than ever! I wouldn't be surprised if our dear Rose rewards our repot with a bumper crop of flowers this summer. 

Risky Rose all leafed out on a bright spring day - April 2021.

3. Blog Announcements

1. Submit your trees for critique or advice here. I need new trees for the next Bonsai Buds episode! Guest announcement TBD.
2. Contact me if you ordered seeds from me last year and they did not germinate. Now is the perfect time to plant!
3. Seeds and bonsai guide for sale! My Bonsai-From-Seed guide is freshly updated for 2021 - get your copy with one of the several new species of seeds that I am selling in bulk on Etsy. 
4. If anyone wants/needs someone to talk about the vaccine, feel free to email me. As the world just passed 3 million deaths from Covid-19 and many countries are experiencing third waves now, I thought I should offer my voice and my expertise as an open resource for anyone out there on the fence about the vaccine. I'm not an MD kind of Dr., but I am in the process of getting a Ph.D. specifically for microbiology in a vaccine development lab. Drop me an email if you'd like to talk about the benefits and risks of the covid vaccines! Here's to hoping for herd immunity worldwide soon.