Happy Fourth of July! There’s nothing like grilled meat, potato salad, watermelon, and the rest of the fixins followed by some fireworks. Except for bonsai, of course. Today I want to tackle what makes a lot of bonsai folks cringe, but which when you master it will pay awesome dividends. By that I mean making roots where there are none and you need some.
When you’ve been in bonsai long enough you’re going to encounter one of the banes of the bonsai artist, namely, bad or no roots. And by this I mean those nice surface roots, what is known as the nebari. Ideally your bonsai, being a tree after all, is supported by a stable and attractive set of roots. There should be at least three, the minimum to produce an impression of stability. But what happens if you have an otherwise really nice tree but the surface rootage is bad or AWOL?
Here’s a classic example of this phenomenon, an American hornbeam, Carpinus caroliniana. What I liked about this tree when I collected it is the rough bark, which is not normal for American hornbeam. With good taper and an unusual growth habit, I thought and still do that this tree has the makings of a great bonsai.
The problem with this tree is that it has an unstable nebari. There are flaring roots on the sides and in back of the tree, but across the front it’s just totally flat. While this can be overlooked or covered with extra soil, that’s really not the solution to the problem. The solution to the problem is to put roots where there are none. That’s right, it’s time to partially layer this tree (*shudder*).
Now, you may be like some when faced with this chore and just avoid it. Truth be told, many years ago when I was new at bonsai I avoided it like the plague. I mean, they make it look so easy in the books and articles. Well, sometimes in order to get better at something we just have to tackle those chores that seem more trouble than they’re worth, rather than avoid the issue altogether. I hope to make it seem a little less daunting to you with this step by step lesson.
So, the first step in the process is to remove the soil from the area to be layered. You can see the flat area I mentioned above. The trunk just goes straight down into the soil, which frankly is ugly. What we need is one or two roots that emerge from this area, ideally not coming straight toward the observer.
Now that I have the area where I need roots exposed, I’ve peeled away a section of bark all the way down past the cambium layer and just into the sapwood (or xylem). It’s important to make this area wide enough so that when the growing callus begins to form it won’t be able to heal over before roots emerge. This is true, by the way, whether you’re doing this type of operation or air-layering to make a new plant.
Notice one more thing in this photo. The top of my cut is made just under the point where the flaring roots to either side begin to flare away from the straight part of the trunk, so they will look like they match up with the others. The new roots are going to emerge from the top edge of this cut. Remember how a tree works. Roots are fed by nutrients that are transported down the inner bark (or phloem) from the leaves. Roots are not made by an upward flow of nutrients, so nothing is going to happen at the lower edge of this cut.
Mix a little water with it to make a paste. And for God’s sake, don’t be as messy doing it as I was.
Next, steal a small artist’s brush from your child or grandchild and “paint” on the rooting powder paste under the top edge of the cut, where you want to stimulate root growth. (You can return the artist’s brush later, when they’re not looking.)
Thoroughly wet some long-fiber sphagnum moss and pack it up against the whole area you skinned.
Wrap the trunk of the tree with plastic film – Saran® wrap works well. You can buy some fruit at the grocery store and put it in one of those handy bags, then when you get home toss out the fruit so you have a bag to work with (just kidding; fruit is awesome). No matter what you use, make sure it’s placed tightly against the trunk.
Next tie above the layered area with some twine, to help make sure it remains moist. Water can flow down the trunk during watering to help maintain the moisture level.
After trimming off the excess twine, add some soil over the edges of the plastic wrap to finish the job. Now it’s time to set the tree aside and ignore it for a number of weeks.
About eight weeks, to be precise. You can usually figure on about this timeframe when layering a tree. Carefully unwrap the plastic, at which time you will typically see new white roots emerging from the sphagnum moss. Just like here!
Another angle and a little closer. Don’t remove the sphagnum moss at this time. Keep it in place, which will help the new roots stay moist. It can be removed at the next repotting.
The final step is to add soil to cover the new roots fairly deep with bonsai soil, which will help keep them moist. You can also add some surface moss to the soil over the spot where the new roots are.
I hope this encourages you to try your hand at layering. It can make such a big difference for your bonsai.