Burying future nebari to encourage growth

[pandacular]

I saw @leatherback mention in a video (don't recall which one, but I think it was about japanese maple) that he had buried the nebari. I believe the reason was to encourage growth. Is this a common technique? What are it's primary goals, just so I don't mis-state them? Are there specific species that this should be done with, or ones that should avoid it?

I've seen lots of discussion on how to prepare roots for a repot to promote good nebari, but not much on how deep to plant them. Thanks!

 

[yenling83]

Yes, you want to keep the nebari under the soil and slowly expose the nebari over time and once the roots have hardened. If you expose too soon the nebari can die or at least greatly slow down, they will develop much better under the soil.

 

[leatherback]

I saw @leatherback mention in a video (don't recall which one, but I think it was about japanese maple) that he had buried the nebari. I believe the reason was to encourage growth. Is this a common technique? What are it's primary goals, just so I don't mis-state them? Are there specific species that this should be done with, or ones that should avoid it?

I keep the nebari covered as long as I can. New roots will only form on parts that are below-ground. And more often than not do I wish for more roots in the rootspread. Also, planting as deep as you can of course reduces the space below the trunk for roots to grow, but that can also be fixed with shallow containers.

 

[pandacular]

It makes a lot of sense! I've only got this one spring of bonsai under my belt, so I'm not sure I really understood much about developing roots when I was repotting. I thought my dinky little surface roots looked cool, so I left them above ground. I'll be top-dressing some of my trees this weekend, and I'll think I'll raise the soil level above some roots in that time.

Also, while I have your attention, I want to personally thank you for your videos. You do an excellent job at presenting, your trees are lovely (without feeling too intimidating), and you cover a huge variety of topics.

 

[Shibui]

Growth can be misconstrued. Growth may mean existing roots thickening or growth may mean more roots emerging.
The 'roots thicken more when buried' concept was very prevalent when I started bonsai many years ago and still seems to have some traction. The more I consider it and the more experience I have the less convinced I am. Trunks and branches do not thicken less because they are exposed. We are all pretty comfortable that trunks and branches thicken in direct relation to how much growth is above them or how much sap flows past from roots to leaves. It seems to me that roots grow and thicken in exactly the same way. Many times I have noticed a correlation between thickest roots directly below a thicker branch or branches and that also applies to roots that are exposed.
ROR with exposed roots do not seem to have thicker roots below soil level. The entire length of root thickens at the same rate.

There is a case for covering nebari if we need more roots to emerge. New, tender roots do not survive if exposed to sun and dry air so new roots will rarely emerge in the nebari is exposed.
That does not mean that more roots will develop if the nebari is buried though. For some species roots can emerge voluntarily (trident maple, juniper) but with many others the tree seems happy to rely on what main roots are already present.

In my experience root pruning from an early age is the single best tool to develop better nebari. That includes root ramification - the majority of new roots seem to grow from the cut ends after root pruning established roots so cutting short is important, which is also very similar to branching above soil level. Significant and regular root pruning also develops taper in the root system and keeps young feeder roots closer to the trunk where you will need them when transferring to a bonsai pot.

 

[Mikecheck123]

I heard Tony Tickle say you should bury them, so I do.

 

[leatherback]

I heard Tony Tickle say you should bury them, so I do.

I think he meant, bring bonsai roots to Bury, where he lives