Root over rock training

I am training a few root over rock trees. I have a trident maple, a gingko and a yew.
They are all in plastic tubes (plastic pots with the base cut out) with a tray beneath to allow roots to establish.
Little at a time, I am trimming the plastic pot to expose the roots on the rock.
My question is, what is the best time of year/ season to be removing sections of the plastic pot to expose the roots on the rock?

I plan to do some of mine after the spring growth hardens. The tree should be back in an energy positive state so it can handle the loss of a few feeder roots. This is a plan and not what I have done.

What i have done is to remove the soil when I repot. In fact, I often repot to inspect and correct the roots over the rock and then recover them with soil. This often involves using some cord or raffia and small blocks to push them back against the rock or to rearrange them a bit. When I finally start to uncover them during the repot, most of the feeder roots are down at the base of the rock and under the rock so I cover the newly exposed roots with sphagnum moss to keep them from sunburning.

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I had success with trident maple during repotting season (early March) and even after Spring hardening.

Also, I would not remove the soil little-by-little, maintain as many roots as possible and reposition the main ones you want to be part of the composition during each repotting. Bury the whole rock along with the roots. Check every year or other year to see if they have reached the desired thickness. Once they reach the desired thickness remove the top soil to expose the top of the roots. The roots will stop growing considerably if you expose them too early. Attached are some progression photos so you can get an idea of the technique.


What kind of material are you using to bind the roots? Grafting tape? Or just some plastic tape?

The white one was Plumber’s Tape, the clear one was Parafilm M ordered from amazon. I used broken pieces of pottery to push roots closers to the large crevices on the rocks before wrapping it in parafilm. I felt the parafilm was easier to work with.


I was thinking the best time would be at the end of summer?

I like a bit earlier in the year for the tree to put some of its energy into converting the surface of the roots from soft and soil covered to more bark-like. They will then be prepared to truly bark up during the fall vascular growth phase. However, I don’t have any real data or even experience to back that up.

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