If you haven’t read Parts 1 & 2 of Air Layering 101, please use the above links.
Now you have the basics down, you understand what an air layer is, why it’s useful, and how it works. I’d like to go over a few scenarios you may run in to that weren’t covered previously. Our first example, a Rhus copallina, or shining sumac, is a great candidate for an air layer.
our air layer host, this sumac is between 12-15 feet tall
The shining sumac is a large bush or small tree. Characterized by shiny narrow feather-shaped opposite leaves, the females bear dense clusters of red fruit during the summer which is an important food for wildlife. Sumacs are somewhat rare in the bonsai world, as they tend to produce vine like branching with long internodes. The skinny leggy growth means finding a specimen with a properly thick trunk suitable for bonsai is somewhat difficult. This is where an air layer on an older established tree is recommended. With a little patience and proper training, the sumac can make a stunning bonsai.
gorgeous sumac bonsai displaying its autumn foliage
I chose this example because I’d like to show another characteristic to look for when choosing a branch for layering. As I touched on in the previous parts of this series, taper is extremely important In fact it’s the most important aspect of bonsai. In order to give the illusion of age and scale in a bonsai, taper must be ever present. Using the bonsai above as an example, taper begins at the base. Wide at the bottom, the tree narrows as your eye follows the trunk line to the foliage. Even at the foliage canopy, taper still is present. The lower primary branches are thickest, and as your eyes follow outward and upward, the secondary branches narrow and split into two, then two again, until the thinnest branches terminate at the exterior of the canopy.
sumac branch with nice movement and rough bark
Notice the sumac branch above. It has great movement, nice aged bark, and a strong foliage mass that’s just out of frame, but after peeling away the lichen to get a better look at it I notice a couple of things.
this sumac has formed a callous to cover earlier damage
There are two things I’d like to point out here. One is the scar on the bark to the right. This usually happens when the tree is damaged or loses a branch. The tree heals itself by growing wood over the damaged area and forms a callous. I would really like to showcase this natural feature on my tree as it would give it character and further the illusion of age. The other point I’d like to make is the raised lump under my index finger. If I rotate the angle slightly, it appears more prominent.
reverse taper showing under my index finger
Why is this worth pointing out? Recall my mentioning taper before and this is why. Taper is the goal in bonsai. Although I would like to have the natural hole-like callous on my tree, I would then have to deal with the large lump directly above it. The lump on this tree would give it reverse taper, which is the exact opposite of what I want. The base of the tree would no longer be the widest part, instead this lump would be the thickest aspect of the trunk. Although I could carve off the lump, I would then have to deal with the resulting large scar which may never heal over completely in my lifetime. So I have to make a decision. I could keep the natural callous feature of this tree and find a way to deal with the reverse taper, either by carving or changing the angle that the tree is viewed at. Or I can forget the callous and use the protrusion as the base of my tree, giving it the correct taper, widest at the bottom and gradually narrowing towards the apex. Since taper is the goal here, and is involved in every aspect of bonsai, I will have to do away with the interesting callous for the sake of a balanced wide to narrow trunk, and create my layer just above it. Even though the protruding lump doesn’t seem that large or significant, I can’t stress enough how important taper is when conveying the illusion of a large tree in miniature form. I won’t go over the air layering process again in detail as the steps are the same. I mainly just wanted to bore you to death with the concept of taper.
the bark is scored below the protrusion and again on the other side of the scar
enough bark is removed to prevent the tree from bridging the gap and healing
- the layer is wrapped with plastic, stuffed with moss, and sealed at the ends
Next I’d like to demonstrate an air layer on a tree that’s already been potted and is too tall at the moment. Below is a dwarf pomegranate, Punica granatum, that was won in a small raffle last month that our local bonsai club holds every so often. It’s still fairly young and currently is being allowed to grow freely. The trunk is still rather thin, and though I could put it back into the ground and allow it to thicken up, I felt using it for this demonstration would be a fun way to point out another scenario you may come across since I don’t really have any plans for it at the moment.
pomegranate that is too tall for its width
As you can see, it looks like a young plant rather than a mature tree. Although this is partly to do with the branching being untrained and growing upwards, the largest culprit here is the thickness of the main trunk relative to the height of the tree. Using nature as a guide, younger trees tend to be long and narrow, spindly with very little taper. Older trees are significantly wider at the very bottom, and gradually narrow as your eye travels to the apex, displaying much greater taper.
notice the difference in taper between the young and old tree
The distance from the bottom to the top relative to the trunk’s widest diameter can be expressed as a ratio. In bonsai, a common ratio that is pleasing to the eye and most mimics a mature tree growing in the field is around 6:1, where 6 represents the height of the tree and 1 represents the diameter of the trunk towards the bottom at its widest point. Measuring the width of the pomegranate, I get a diameter of approximately 1.5 inches. Using the 6:1 ratio, this would give me an ideal height of around 9 inches.
the width of the diameter is around 1.5 inches
Measuring the height, I have a distance of well over 12 inches. Because of a relatively long height to width ratio of this particular tree, I am left with the appearance of youth instead of age which is not a quality that I want.
a height of 14-15 inches is undesirable for this tree
Most of the time in this circumstance, a simple trunk chop would be in order, removing the top most part until a satisfactory height is attained. In this case, because I am quite fond of the nice amount of movement of the upper portion of the tree, I will remove it with an air layer and pot it to make a separate tree.
Luckily there is already a branch in place which will be my new leader. Counting the trunk plus a few inches of the new branch leader which will become my future apex, my tree will be approximately 9 inches tall. The leader branch on the right will be allowed to grow freely until it thickens considerably, then chopped back to a satisfactory height. This will further the illusion of taper in the pomegranate.
the top will be removed at this point, the right branch becoming the new apex
The steps for creating the layer are identical to the process I’ve outline previously. The main purpose of this small air layer demonstration is to point out how taper and the ratio of height to width can produce the illusion of greater age of your bonsai.
the bark is scored just above the new leader branch
the bark, phloem, and cambium are completely removed
the wound is wrapped with damp moss and plastic
Once the bag has filled with roots, the top will be removed and placed into a pot of its own. There is no need to use special soil with newly rooted air layers. Use standard bonsai soil, a recipe for which can be found on the soils podcast. Make sure the new layer is very secure in its pot, as the delicate young roots will be quite fragile and susceptible to damage by any movement until they are established.
That concludes this tutorial. Remember to always keep your eyes open when in the field. Nature will provide you with countless opportunities to create the perfect bonsai from her raw material. Whether from an entire tree, or an air layered branch, art exists within the wood all around you. And don’t forget your doggy.