Root Grafting Pines

Root Grafting Pines

Japanese White Pine, Pinus parviflora, make particularly bad grafts, especially the dwarf cultivars since the understock soon outgrows the scion portion and necks down abruptly. Sometimes they are grafted onto Japanese Black Pine, P. thunbergii which of course has totally different bark. If this is done for effect it is usually grafted about four inches up and the trunk bent at the union. It gives the appearance of great age but the abrupt transition of bark types has always bothered me.
Other than this style, the grafts should always be low. It is very difficult to obtain low grafts. 99% of the pine grafts are made for landscape and not bonsai, so it takes a nursery dedicated to bonsai or one which is sensitive to the needs of bonsai enthusiasts to produce good bonsai grafts. A few large nurseries that produce the bulk of grafted pines in this country have been persuaded to produce some grafts for bonsai, so things are beginning to change.
The very best grafts are 'root grafts'. The scion is not actually grafted to the roots, but rather to the stem tissue below the 'crown' that forms when the seed emerges from the shell. This is a small ring of tissue on the stem that clearly marks the division of root type tissue (was the radicle of the seed) and the true stem which is capable of producing foliage. On pines and cedars this 'root' portion of the stem can be very long, as much as six inches or more before actual roots appear.
For bonsai the seedling understock is potted up high so that the root portion of the stem stands several inches above the pot. This makes is easy to do a low graft. The graft can be placed just below the crown ring and after the graft takes, about a year later, the whole thing buried so that the graft sits right at the soil line. Since the buried stem portion is root tissue it can stand this procedure and has the possibility of forming roots. Grafted in this fashion the union will blend perfectly into the nebari (crown and surface roots). Also, since there is usually a bulge for dwarf cultivars, what was once a liability now becomes an asset since the swelling will be right at the crown.

If your graft is below this ring of tissue, you may bury it up to the graft. If it is above the crown ring you can still bury it, but you must be much more careful. It is akin to air layering. Bury the stem section in sand after making some vertical slices in the stem where you want roots and treating with hormone. This will work for all pines that are 'low grafted', that is have a graft only an inch or so above the crown ring. If the pine is 'high grafted' it will have to be air layered.
I recently went to a local bonsai nursery and checked out the potted up White pines and the grafts were hideous. Very nice little styled trees, a dwarf cultivar, grafted onto white pine with the understock about twice the diameter of the scion with no effort to conceal the graft.
This procedure also applies to Japanese Black Pine cultivars, Pinus thunbergii, as well, and is especially important for the rough bark ones. There is nothing more ludicrous than a nicely styled Nishiki Kuromatsu with two inch bark wings floating above a relatively smooth lower understock section. To get really picky, the very best rough or cork bark black pines will be grown from cuttings so even the surface roots will show the corking. I have a rough bark Japanese Maple, Acer palmatum 'Arakawa' that has such corked surface roots (cutting grown). It is quite amazing.