Getting to the Roots: Forsythia tree Soil examination [Bonsai]
Looking back from the past, today I am sharing photos of this Forsythia tree I am training for bonsai.
On this day in early October 2019, I picked this tree to make an important decision. The big decision I had to make was, should I transplant this tree to a new pot with new soil, or not?
This tree has been in this pot for about two years now. After a few years, it is usually wise to check out the roots, and make sure the tree is not running out of space inside the pot. A tree that appears weakened might be overly root-bound.
The moss has grown into a mounded tuft. Now the moss is brimming above the rim of the pot. This is causing water to run-off from the surface instead of down into the roots and soil. The moss is receiving more water than the tree, and this can negatively affect the tree.
In hot tropical regions, some people grow their bonsai trees in pure sphagnum moss to keep the roots moisturized so it does not dry out.
In my climate, we have the opposite problem. It is recommended to grow bonsai using almost no organic matter in my cold/wet climate. With all of the rainfall we receive, the moss and mold grows very quickly. Soil must be changed when necessary to ensure it always has perfect drainage, allowing water to quickly pass through.
I usually save the old soil I remove, but I have not found a good way to clean the rocky bonsai soil free of the mossy organic material. If anyone reading this knows how to do this easily, let me know in the comments below. Maybe soaking old soil it in a bucket of soapy water would work.
I decided to do a scratch test on the soil and find out how much mossy soil can be removed. It is safe to scrape away all of the surface soil until you find live roots and a good quality layer of bonsai soil.
Many golden yellow live roots are threading through a quarter inch underneath the moss. I discovered this tree had healthy roots under the entire moss surface.
This is a good sign of health for the tree. These water roots are allowing the tree to quench its thirst whenever it needs to. In a way, the tree has adapted to find water just under the moist moss layer.
I am not sure if the deeper roots of the tree are receiving enough air and water, but the soil underneath the moss seems to be filled with plenty gravel, and the tree appaers healthy. I think it will be okay to leave the rest of the roots undisturbed.
This tree does not need to be transplanted so long as I clean off all of the top layer of moss.
A layer of pure pumice gravel is filled over the exposed roots on top. No akadama clay was added, because I want to discourage more moss from forming on top again.
The tree was watered daily for the next week or so, allowing the roots to start to adapt to the additional air and lack of moss covering on top. With winter on the way, this will allow the lower protected roots to kick into growth action after the leaves fall off, and the tree goes into dormancy.
Roots continue to grow when a tree is dormant, and a good bonsai pot with good bonsai soil can encourage a tree to grow many small roots to fill the space. Smaller roots will also encourage smaller leaves and smaller branches to form.
The new layer of pumice I added is very flat and even. Water should irrigate into the soil easily.
The trunk nebari is visible and developing into a interesting ball shape. With strong roots, this will become a deep and wide base for the tree.
To me, my tree resembles an exotic tree from a desert tropical Asian climate, while in truth this tree is native to cold and wet regions. It has a little Buddha Belly. The bumpy, wiggly branch and the growth ridges on the trunk are giving the young tree and aged appearance.
That's it for today's show-and-tell. Thank you for joining me in this fun hobby demonstration.
Photos in this post are all #originalworks by 
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