This article illustrates the technique of grafting a new root system onto a field-grown Field Maple or Acer campestre that had been developed in the ground for 5 years.
It is strongly advised that the article ‘Approach Grafting’ is first read and understood before applying any techniques described in this article. A second useful and related article is ‘Threadgrafting New Roots’; both threadgrafting and approach grafting new roots are equally viable techniques and should be seen as techniques that can be used individually or in conjunction with each other.

 

This Acer campestre started life as a pencil-thin sapling in 2000. It was planted into the ground and allowed to grow freely for 5 years to encourage rapid thickening of the trunk.

At the time of planting, the sapling had a tourniquet applied above its existing root system to encourage a better nebari (surface roots) to develop as the trunk thickened in the ground. (For more details of this technique please see here). When the tree was harvested from the ground in 2005 (see image above), the tourniquet had produced very mixed results.

 

 

Spring 2005: After pruning of the rootsystem. The tourniqueted roots had, as required, all appeared at the same height on the trunk and their appearance was acceptable. However I felt that they could still be vastly improved. Only three thick, untapered roots were visible from the front of the tree and roots were largely absent at the back of the trunk altogether.

The newly harvested Maple was planted into a nursery container to allow the tree to recover with a view to carrying out further work on the roots in the following Spring.

Spring 2006: A year later and the tree had recovered from the previous year's harvesting and root pruning well, and as is typical with all Acer species, had rooted strongly through the year.

The image above shows the back of the tree with its surface roots uncovered during repotting. The original wire tourniquet can still be seen embedded into the bark. Though there are roots at the back of this trunk, they are too low and new roots are needed in the middle of the area circled in red to create a radial root spread.

I had tried to prompt new roots in this area during 2006 by drilling holes in the trunk (these are then filled with rooting hormone and can sometimes prompt new root growth around the wounds). Unfortunately, in this case it had just prompted a sucker above one of the three holes.

A few months later in June 2006 I approach-grafted 2 saplings to the front of the trunkbase and a further one at the back of the tree.

Notice in the image above that I had also 'split' one of the original thick surface roots. By removing a large amount of wood straight down the centre of the root whist retaining its sides, I had divided it into two live halves that, as they healed, became two new individual roots. The purpose of splitting the root like this was to create some root taper and ramification.

Another year later in 2007 I approach-grafted a further 4 saplings to the back of the trunk in order to produce a complete uniform surface roots around the base of the trunk.

In the image above it is possible to see aroot that has been grafted but not yet sealed and the tiny brass screw holding the sapling in place while it grafts into position.

 

Spring 2010: 3 years later and the grafts at the back of the trunk have healed well. Having been allowed almost free growth since 2006 to encourage a strong graft-union, the graft stock was then pruned back hard in early 2009 to encourage the sap to flow into the main trunk rather than continuing into the top of each grafted sapling itself.

 

Spring 2010: with all but one of the grafts having taken, I removed all traces of the original saplings and sealed the wounds (pruning Acer species during the Spring can result in bleeding or sap loss and I prefer to use wound healer to prevent this). On the right of the picture above it is possible to see where one of the grafts had not been secured tightly enough against the trunkbase during the grafting process and had therefore not successfully taken. I will graft a new sapling into this area later in the year.

With the tree taken out of its training container, it was then bare-rooted so the root system could be pruned thoroughly. Notice that in the image above the tree still has some of its original rootbase.

Now that there is a sufficient surface root structure to support the tree, as much live wood as possible was then removed from the base of the rootball using a combination of knob cutters and a carving tool.

This technique encourages new roots to emerge from the existing surface root structure, in turn creating a flatter root system and better development of the nebari and trunkbase in the future.

Close-up image of the thick front root that I split into two in the Spring of 2006. The two approach grafts at the front of the tree back in 2006 have not taken 100% and have simply been pruned back hard for the time being and will be allowed to grow freely throughout 2010 to ensure they graft securely.

After removal of the base of the trunk and along with it, all of the original saplings rootsystem has produced a flat rootsytem

Spring 2010: Finally, the Maple was potted up into a large mica training pot while the branch structure continues to be developed.

Current height of the tree is 12"/30cm, with a trunk diameter above the roots of 3.5"/8.5cm