Advice Young Japanese Maple

[Mr.Dr.K]

I have this young Japanese Maple that has been in the current Root pouch for two growing seasons; it does feel like there is probably more room in the pot for another season. ATM, I am just allowing this thing to grow out and fatten up. There are a few larger lower roots/branches that I believe will help bulge the lower trunk. My question is, should I leave the roots alone another season, or prune this Winter?

 

[coachspinks]

You have a couple of options here. One, cover the roots and let it go another season. Those surface roots will thicken if they are covered. Two, work the roots now. The correct time to do this is when you repot as the buds are opening. This tree looks about ready.
A couple of thoughts, building the root spread is one of the important first steps toward building a tree. One way to help a tree along is "planting" the tree on a board. The Ebihara is explained very well in this thread by MarkyScott. The roots you have there may already be too big, maybe not. I'd probably try. If you wait another year, I feel sure they would be too think.
Someone may comment that this tree might be a good candidate for a ground layer. That may be true, but I would encourage you to try the Ebihara technique first. It is a good skill to learn.

FYI - that lowest branch is growing below the graft. I'd cut it off.

 

[Dan W.]

I agree with @coachspinks . It’s best to get the root structure set exactly how you want before allowing the tree to thicken too much. You can always layer later, but if the current roots can be worked in a way that you like, you save yourself an extra step.
This way you continue building the tree and the nebari at the same time. Historically, far too many pre-bonsai (in the US) have only had their nebari worked as an after thought. Much better to build it right the first time.

 

[liltrees]

Not much to add that hasnt already been said. When you repot, you can choose to trim a few of the surface roots. This will tell the tree to send out more (smaller) roots in their place. In time this will also increase the nebari.

Nice little tree!

 

[Dan W.]

FYI - that lowest branch is growing below the graft. I'd cut it off.

I could be wrong, but I don’t see a graft, and those low branches seem to have the same growth pattern.
I would guess that this is a seedling from a Mikawa type.

 

[coachspinks]

I could be wrong. From the difference in bark and the subtle change in direction, I assumed it was a graft. It may just be the natural progression of the tree developing bark.

 

[liltrees]

Not much to add that hasnt already been said. When you repot, you can choose to trim a few of the surface roots. This will tell the tree to send out more (smaller) roots in their place. In time this will also increase the nebari.

Nice little tree!

Just wanted to add this diagram from Yuji Yoshimura. It is a good reference/example of angling cuts when you trim surface roots so they will regrow properly and not end abruptly

 

[Mr.Dr.K]

Very interesting, thank you all for the insight and the link to the thread. It makes sense to start now and progress the roots with the tree. I'll see what I can find locally this weekend and maybe give this a shot. Cheers.

 

[River's Edge]

I have this young Japanese Maple that has been in the current Root pouch for two growing seasons; it does feel like there is probably more room in the pot for another season. ATM, I am just allowing this thing to grow out and fatten up. There are a few larger lower roots/branches that I believe will help bulge the lower trunk. My question is, should I leave the roots alone another season, or prune this Winter?

At this stage of development you should repot and prune the roots for improvement every two years. Set the structure in the early development for best long term results. providing the tree response each time and is healthy and vigorous before the next time frame.

 

[Shibui]

I could be wrong, but I don’t see a graft, and those low branches seem to have the same growth pattern.

I agree. I cannot see any evidence of graft on the trunk and the close internodes of those lower shoots are identical to the rest of the trunk. This is almost certainly a cutting or seedling.

There's very likely plenty of room in the pouch for another season but I agree that nebari is important for Japanese maple bonsai. @River's Edge put it very well - 'Set the structure in early development for best long term results'
Looks like this may have been simply transplanted into the root pouch without much thought to future roots and nebari. Now would be a good chance to set that right, before the roots get too thick, before the top has developed too much.
While the Ebihara board technique looks amazing to beginners, it does have some drawbacks in practice so not every attempt works as well as proponents would have us believe. We can achieve very similar or better results by good root pruning with less bother IMHO.

There are a few larger lower roots/branches that I believe will help bulge the lower trunk.

The thing I find bulges lower trunk most is a good nebari. When all the tree's resources come from lateral roots all around the trunk those roots and the lower trunk tend to swell much more than when the tree has down growing roots supplying some of its needs. Encouraging a good, well spread, all round nebari seems to be win/win.

I would encourage you to root prune this Winter/Spring.