Sidesummy's JBP & JRP Ground Growing Progression

[Sidesummy]

I have done something similar to Option 2 above with a shovel to slice through the ground/roots around the trees. However my trees (JBP) were only planted 2 years prior, so the roots presumably weren't as thick/advanced as what I am imagining you will have. The results were good. I left them for a further 12 months and successfully transitioned them from the ground into shallow plastic training pots with a nice amount of finer roots close into the trunk. I didn't lose any trees in this process. I feel you might have a potential issue with thicker roots extending out quite a way before the finer feeder roots emerge from them. The only way to resolve that is to cut back so I think any plan to reduce the root ball while they are still in the ground is better than nothing. Healthy fine roots close to the trunk/nebari are key to giving the trees a solid future as bonsai. I absolutely think there is a good chance you can still achieve that ... good luck with them!

Any suggestions on timing from your experience? I had though early spring made the most sense to me. But here's some of my rational:

-Early Spring when buds begin to swell? This would be similar to a repot I suppose where root work is being done and roots are being cut.
-Middle of the growing season? Tree is vigorously growing, might be able to send out new roots easily because everything is growing right, why not the roots too?
-Autumn after needles have hardened for the season? Seems like the worst possible time if the tree has sent all it's resources back towards the roots for safe keeping during the winter. Probably shouldn't go cutting them at this time as I feel it would weaken the tree for the next season.

I guess I just feel torn, should I do it in spring or in the middle of the growing season.

 

[Ryceman3]

Ideal timing would be when you usually root prune. For me this is mid/late July (as things begin to move after winter) and that is when I did the shovel work. The other time I would consider it is early autumn, because in my climate there is plenty of time for new roots to grow and strengthen before winter (which is pretty mild for me anyway). Being from Australia, I don't really understand/relate to the USDA zoning, but I am guessing Zone 6a is a fair bit different to 9, so you would need to take this into consideration and use your own judgement. In the middle of the growing season, I can expect temperatures of 40degC (104F) so I wouldn't be overly keen to cut pine roots then, but this may not be the case for you...

 

[JeffS73]

Only just seen this thread, very interesting and great job so far!

Like Ryceman, roots would be what I was thinking about. If you're giving yourself 2 years from digging up, why not dig the trench 180 degrees instead of 360 in year 1, then do the other side year 2.

My experience of repotting JBP so far is that although they are vigourous, they aren't as robust as some other species. When I've trimmed half they've recovered much better than doing the full 360 in one go. I feel like I'm still a ways off understanding them in my climate, UK, zone 7-8.

 

[tanlu]

Great Question. I'm somewhat embarrassed to say that they remain untouched since they were moved from their seedling beds up until today. In my growing beds I was able to thread my deciduous material through some tiles which I drilled a hole through, but with all of the pines being 2 years old by they time they had side shoots and I couldn't get them threaded through the tiny holes I put in my tiles. i.e. all the pines "probably" have a nice big tap root going down into the ground which I'll have to contend with someday. Over the years I've thought to myself about how best to address that root situation in the future. To my credit I did amend the soil with a large amount of haydite mixed in with the native clay'ish soil. So the digging a trench around things when I want to lift a tree should go fairly easy. In fact, when I moved to my new home 2.5 years ago I dug up 1 tree which I felt wasn't going to be great for bonsai but might be nice as a garden style niwaki tree (it happened to be a black pine) and it came up fairly easy. For the life of me though I can't remember exactly what the roots looked like and I didn't take photos. What I do recall though is that the haydite/clay soil mix was more-or-less falling right away from the roots and I was doing my best to be as gentle as I could so as not to bare root the whole things. My goal at that point was to disturb the roots at little as possible and keep as much soil on the root ball since I was just trying to move it, not shrink it down into a bonsai pot or training box.

As for my plan with all the pines in the future, I'll tell you what my current thinking would be, and I'll welcome any and all input from those who might have some experience or a hunch as what might work best. But here's my idea:
-2 years before I plan to dig up the tree and put it in a bonsai pot/box I plan to roll back all the ground cover around the tree.
-I'd do one of the following:
1. Go roughly 12" radius from the trunk of the tree and use a reciprocating saw (saws-all) and hold the blade perpendicular to the ground and just walk a circle around the tree cutting straight downward into the ground. Basically severing any roots growing horizontally within a foot of the tree, but do nothing to anything deeper than say a foot from the surface or underneath the tree. (i.e. continue to ignore any tap roots) until the time to fully dig the tree comes.
2. Go roughly 12" radius from the trunk of the tree and use a shovel/pickaxe/other to dig a trench at a downward angle towards the area underneath the tree in the hopes of finding and severing the tap root. Basically making a big old root ball like those you might see wrapped in burlap at a garden center. However instead of lifting the tree at that point refill the whole trench with the soil. This method I figure would allow me to know that there are not roots uncut outside the size of my digging, and would allow the tree 2-years to rebalance its root ball mass that will likely be more densely filled and compact that what it currently is.

In all likelihood I will probably do a few trees with each method on lower quality trees (the benefit of planting so many) and seeing how the trees respond. Hopefully neither results in all the trees dying, cause I'm hosed if that's the case... *nervous laugh*.

First off, hats off to you for this effort. I’ve grown half of my trees in the ground, (although we’re talking just an handful of plants…nothing compared to the scale you’re doing) and have learned a lot from that process. The benefits are obvious and with a bit of logic and foresight, the transition to pot life isn’t that challenging.

I also went with something similar to option 2. I’d recommend this method to others interested in ground growing pre-bonsai because it’s easier for any able-bodied person to do and doesn’t require specialized tools or skill. Although, my timeframes were different.

My trees have been in the ground since 2011 and were planted as seedlings. I had less control over their care since they were planted at my parents house (I’ve been an apartment dweller until 5 years ago) and I was flip-flopping on the hobby while still in school. I was also growing a few non-grafted JWP that I wanted to grow out and develop a bit. I potted 3 of those trees in spring 2024 and 2 of the 3 are going well in bonsai soil. The JRP has progressed much more quickly it its pot, but while in the ground, interestingly, both the JWP and JRP seedlings progressed at a similar rate.

I may put in the ground at least a few more young trees since I still don’t have a lot of growing space or a plan for them. As a bonsai hobbyist with a busy schedule, I find ground-growing allows me to continue to improve my trees and grow my collection in a sustainable way.

I’d be interested to see how your trees progress once they’re ready for pots and what approaches you take, as I certainly could learn from that.