Thursday, January 24, 2019

Bud Grafting an old Japanese Boxwood

Japanese Boxwoods are such a ubiquitous planting in the urban environment that many bonsai people tend to discount them as being great material for our art. Others have tried collecting older specimens only to find them frustrating to coax into a bonsai form.  Older Japanese Boxwoods (Buxus microphylla), at least here in Central Texas will typically only bud out on places with active green growth or from dormant spear-shaped buds clinging but sleeping inside the canopy. I've already posted about his problem before with an early solution, thread grafting.  This is a successful way to introduce new growth to barren spots, but since about 2014 or so I have had success with a much quicker way: Bud Grafting.

Here we have our older "urban yamadori" boxwood.  I collected this approx 45 year old plant as part of an Austin Bonsai Society club dig in Spring 2018 and have let it grow all it can in the 8 months since then.  It has a good shape, and from this angle it looks full, but those looks are deceiving.  It has many branches which are totally bare except a little puff of green out on the tip.



Let's start with this bare spot on one of the branches which needs a foliage mass to break up the straight line and to add some future twigginess in the region


Next we select a good scion from a Boxwood mother plant. Successful bud grafting is done when these emerging buds have begun to swell but they still have the familiar brown lance shape and have not opened into leaves. Here are some ideal ones, and the ones we are after are the pait which are 2nd from the top:


Here is the look of the scion branch I harvested. Note that it is a strong thick stem with rigid leaves and is pest free.


We begin by stripping the lower leaves under the buds we will be using. This is the front side of the twig.


Flip it over to the back side of the twig for this first part.


With your grafting knife, make a low angled long slanting cut from the base of the leaves/buds to the next joint.  Cut against a clean cutting board or even better, on a piece of glass.  Be sure to sterilize the board and your tools in between trees so as not to spread germs from one plant to another.


The bottom should now be separated


It should look like a long slanting cut along the back of the stem


Flip it over and on the front side make a short slanting cut down to the tip to put an angle on the end of this side


It doesn't have to be very long, but this slice needs to be cut well to fit it in later. If the end looks ragged after cutting, recut it so that the end is clean.


Looking from the side you can see this shorter slanting cut.  Do not touch the exposed cut areas. Skin oil and other contaminants may cause the graft to fail.


Next with a sharp pair of shears cut the top from your bud scions.  We only want to use two buds and two leaves.  More than that and it can be too much for the graft to keep alive while it is bonding and the chances of success are lessened. We are keeping the bottom part here:


Next take your grafting knife and make a shallow slanting cut on the area you would like a new branch to grow.  Always have the open end of the cut towards the top of the tree, never upside down.  You just have to go deep enough to separate the outer layers from the inner wood. If you try to go too deep the knife will just get stuck in wood.  If  you go too shallow, you will quickly carve off this piece of living tissue.  It may take a few times to get the hang of it.


Looking at the inside of the cut you will notice a few things.  The dark center is the inner wood of the tree (Xylem and heartwood). The inner green band is the cambium and this magic layer is what we are looking for.  You'll see it looks like a upside down horseshoe. You have to line one of these sides up with the scion


Here the scion is placed inside, along the lower part of the green cambium band.  Notice it is facing forward (backside to the branch). Slide the graft into the opening, pushing it down until the point is at the bottom. Then carefully close the flap.  It will hold itself in a little if it is a good fit.  On a molecular level, the two edges of cambium are now beginning to bond.  This is why you really need to get it in there in one smooth motion and not reposition it. If there is too much movement or if you have to take it in & out several times, the chances of success are reduced.


There is a wonderful material used in the medical industry called Parafilm.  It's basically a stretchy waxed film.  I buy a box like this and use it for years and years.  I cut a section that is about 1 inch wide and use the 4 inch length.  One of these for each graft. If you don't have this, there are many types of grafting tape online and I have even known people to use plastic stretch wrap (like the stuff used in the kitchen).


Start at the front and wrap it around the cut area to hold the base area tightly together. Notice the entire stem is under the flap of wood we made on the branch, and the buds are sitting right at the top as if they grew on the branch from the beginning.  This makes a very smooth graft transition.  Many grafts we see are for fruit trees and such aren't concerned with aesthetics, but in bonsai it's paramount.


Here it is wrapped a few times around the bottom.


Next take the wrap up and over the buds and also encase the leaves.  On your final turn, re-wrap the base again and pull and tear the Parafilm free while smoothing it down with your fingers. It should stick together for you here.  By wrapping the entire area up it cuts down on water loss and holds everything firm so it will not move.  Note: use several layers on the bottom stem section but only 1 layer over the living buds.  By using Parafilm, as the buds begin to grow and expand, they will usually burst free of the thin delicate layer by themselves, getting to light and air when they need it.


For the outer wrap I use a flat plastic raffia-like material which you can get from Asian grocery stores.  Really though, just about anything will work (ribbon, tape, cloth, raffia, etc) as long as it is a wide material to put pressure evenly along the length of the graft.  Tie at the base so that the Parafilm doesn't unravel and it also adds to the pressure to the graft union.  Don't tie so tightly it cuts off the circulation though.  I've done this in the past and all those grafts failed.  This will stay on for between a month and 3 months.  When the brown buds have opened into small green leaves and begin to expand, slit the top of the film down to the buds and gently fold back the flaps.  The next week pull the top section off but leave the tie and wrap at the graft for week.  Next remove the outer wrapping but leave the Parafilm for now.  Remove all of the film as the buds elongate and turn into twigs. 


One year old bud grafts. After about a year, the grafts will be alive and expanding, but are usually slow the first year.  Remember the old garden saying: First year it sleeps, second year it creeps and third year it leaps.



On the second year the base will begin to lignify and the melding of the scion and stock will be further along.


A few years in and the graft union begins to disappear as the camiums have merged into one.



Several years down the line and you will be very hard pressed to know which branches were naturally produced and which were grown by grafts.


Keeping a good "mother tree" of a plant you want to harvest graft scions from is a great idea.  This is an old Japanese Boxwood I have in my yard which is always free of disease and bugs and produces great buds.


In mid January here in Austin the wonderful fresh boxwood buds have swollen but are still tan colored and are ready now to be harvested and used.


Here's a good one.


And these buds right above my finger are the ones to use.  Such a tiny section, but to find healthy buds near the end, but not on the tip, on a section which is healthy and robust, but also not too early and not too late means that you may have to do a patient slow search for the best ones to use and harvest them only as fast as you can use them.  Old scions aren't the best for grafting. Fresh from the plant is the way to go.


Here is my collected boxwood again after dozens and dozens of bud grafts were applied.


Try to spiral around branches when grafting so that they aren't coming out all at one side or place.  Also basic bonsai design still applies: we want branches on the outside of curves and we want them to radiate from the middle, not to have branches start on an outside branch and go in. Also, do more grafts than you think you need.  Even in the best circumstances, the success rate is 8 or 9 out of 10 grafts will take.  Sometimes it is a problem with the scion, a weak section of the stock, fungus or germ attacks, dust or other contaminants get in the way, or just plain bad luck.


I'd like for the eventual outline of the "finished" tree to be something like this, so pushing growth further back will allow me to shorten these branches and to have more material to manipulate.

As you can see, the technique isn't too difficult at all, but you have to get used to the feeling of movement when working on grafts.  Be very careful not to cut yourself; never put your hand or finger in the way of the blade.  I feel that if more of us are armed with a way to overcome one of the big obstacles of Boxwood as bonsai, that more of the wonderful material out there being trashed by homeowners would find its way into our hearts and gardens.

2 comments:

  1. Joey,
    I just got the link to your blog entry on boxwood grafting from Dr. Hoe. On a Zoom presentation I made on air layering for the May 2nd virtual meeting of the Houston Bonsai Society I happened to mention my interest in promoting back budding on a boxwood I have. I think your blog tutorial is quite good... detailed instructions and excellent photos. Can grafting be done later in the year or is success limited only to early in the year?
    Thanks,
    Alan Raymond
    amraymond@suddenlink.net

    ReplyDelete
  2. Hi Alan! Thanks for checking it out. Grafting can be done anytime you have the correct buds on the host plant (tan colored, swelling but not opened). Spring is the optimal time with the highest success rate, but other times will work too. Sometimes late grafting will take but the buds will not open until the following Spring.

    ReplyDelete