The Nebari
I was listening to a bonsai podcast on my way home the other day and the discussion turned to the nebari and the importance of it to making a quality bonsai. The nebari, or surface rootage of a bonsai is, in my opinion, the most important and determining feature on a bonsai. After the initial outline or silhouette of the tree, it is the first place most of us will look to when we first gaze upon a bonsai.
The Japanese word, nebari, simply describes the surface roots of a bonsai. The nebari gives us a sense of age, stability and maturity in our bonsai. Young trees that are growing in the ground will not have surface roots visible,et as time goes on and the tree grows soil around the base is washed away, the roots thicken, and the nebari of a ground grown tree will start to show. As more time passes, these surface roots show more and more, fusing with each other and thickening. Some of the giant figs in the Royal Botanical gardens in Sydney have extreme buttressing nebari, which rise well above the soil surface. Some trees have more prominent surface roots than others too, with junipers and some of our natives having deep set roots rather than surface roots.
The roots should radiate evenly around the base of the tree and should not stick up out of the profile created. Having them all at one height not up and down the lower trunk makes for a smooth transition into the soil substrate. We only want to see the top part of the roots. The roots should be evenly thick as well, as like branches, they can become out of proportion to the tree. They will overpower other roots and take over, ruining our ‘even’ nebari, therefore we need to cut back heavier roots when repotting to allow other roots to catch up. In saying this, roots that have no variance in thickness can seem boring or monotonous and so I like to have many sizes to make it more appealing. Just don’t let one or two dominate the rest.
There is a bonsai style, Neagari, that is known as ‘exposed roots’ style. This style evokes a tree that has been hit by flooding or some water course over time and this has washed out the soil and exposed the root system. The roots lignify with exposure to the sun and form a structure that holds up the tree. It is a unique and not commonly seen style that is very dramatic and thought provoking when done well.
The nebari is also the foundation for designing the tree. We are taught as a beginner to ‘feel’ around for the surface roots with our fingers when we are purchasing a potential tree. Whilst the ideal is an even radiating spread of roots, this is rarely the case, unless buying from a bonsai nursery that does work to their stock during the formative years of development.
Certainly trees purchased from commercial nurseries or garden centres will have had zero work done to the roots and the first few years of bonsai training will involve repotting to correct faults in the nebari. Trees with a more uneven nebari or ones with a prominent root can be styled into slanting, semi-cascade or cascade, or any one of the many other styles that we choose to design our bonsai as. Roots that show compression or extension give us clues to the future design options for the tree.
So how do we improve our nebari? Repotting. It is the number one time to sort out the roots. Roots growing down are removed in favour of lateral roots to promote a flat and wide nebari. Untangle any crossing roots and cut back strong roots to more evenly distribute the strength. This will make the roots split and ‘ramify’ on the surface further enhancing the look. You can wire roots into position if required or use bamboo or cork to manipulate them. Should the trunk have large areas with no roots, grafting is an option, either approach or thread grafting with stock material. Another method is to drill or cut out a part of the trunk where there are no roots and apply rooting powder or gel and then cover with sphagnum moss and wait for roots to grow. Some species won’t respond to this and so grafting becomes the viable option. I have also seen rocks used to fill the gap in a nebari which can be quite effective. Aerial layering of some trees is also great way to start from scratch when the existing nebari is not good. This is species dependent though.
Another podcaster mentioned that a nebari forms over many years and is not a ‘true’ nebari until the roots fuse and meld together to form more plate like surfaces at the base of the trunk. Certainly the nebari matures like the tree does with time and I can understand this point of view. The picture of the trident maple from Fuyo-en in Japan at the start of the article is taking it the extreme! This feature is either loved or loathed! I've heard the term ‘pancake’ nebari used to describe these large nebari spreads.
After all that, Penjing and Vietnamese Cay Cahn interpret and appreciate a good nebari very differently to the Japanese. Both styles highlight the nebari in different ways and it is often very dramatic and the prominent feature for the tree. What would be considered unusa- ble or grotesque root formations for a Japanese bonsai are sought after. Crossing roots abound as well as high and deformed ones.
However you choose to grow the nebari of your tree is entirely up to you. I have trees which I grow with a Japanese bonsai approach and others in a more Vietnamese/ Penjing style. Whatever you do, consistent and diligent repotting is the best way to improve it over time.