While the climate in San Francisco doesn’t encourage the type of summer-long unbridled growth in Elm trees that might happen in hotter areas, for a few months every spring we get some pretty good bonsai weather. Elms are similar to many other deciduous trees in how they can be worked in April and May, taking advantage of Spring growth. You will find multiple opportunities to improve the structure and fill out the silhouette of a well-growing Elm.
The Elm I'm focusing on in this case study had been hanging around my yard for a few years without me giving it much attention. Initially I hadn't been able to get started on the branching because I needed to add a trunk section. The tree is an air layer – there was a lower section of the trunk that had no additional taper and was layered off the base. Unfortunately, I don’t have any photos of the process.
The tree had about a 4″ girth which ended abruptly with a large chop followed by a short trunk section that was less than an inch in diameter. It made for an awkward transition, so for two growing seasons I planted it in the ground and allowed the top to grow without pruning. When I dug it up and put it into a box, I cut off all the branches and chopped the trunk down to the point where it would provide the best taper possible, leaving only about two inches of the new upper trunk that I grew.
March after a trim and wiring the branching.
Even after two years in the ground there is still work to be done on the trunk taper. I used a large sacrifice branch to fatten the next section of the top to further smooth the taper out. The wound from the last cut also needed to heal, which happens most quickly when a large branch or the top is left to grow out.
I find elm branching in it’s formative stage to be a frustrating thing to work with. The tree seems to make pretty large bulges whenever you make a cut larger than just a small twig. To me that means that I can’t make a mistake from the very first time that I start working on a branch. From a strong cut point the tree will frequently put out three shoots, all of which are too vigorous to really make good branching. Those three are typically removed in favor of slower-growing shoots that are further back.
One month later, at the end of April.
When initially wiring the sprouts that come from the trunk after cutting off all the branching, I was careful to set them at the correct angles based on the design of the tree. If the angle and movement directly from the trunk aren’t correct then the branch will have to be removed years later and much of your effort will be lost. Since the tree wasn't planted at the correct angle in the box – it’s leaning over a bit too much – each time I work on it I have to prop it up at the correct angle to make sure that as I’m positioning the new branches they are at the correct angles relative to the trunk. I deduced the correct angle by the relationship of the branches to each other – the correct angle for the trunk is when all the branches have about the same angle to the trunk.
January: (Left) This front doesn’t have quite the flare at the base but the movement seems better to me. (Right) This potential front shows a wider base but slightly less movement in the trunk.
Once I set the main branch angle and added some movement with wire, then the tips are allowed to run, to fatten the branches. The cut points should always be facing downward; plan a section of the branch where the movement goes down, allowing you to cut to an upward growing bud that is sprouting from behind that section. Elms bud out pretty reliably but they don’t bud everywhere. I’ve found that on this tree it was a mistake to wire out the branches with all the leaves on the sides of the branches. Instead, I used the wire to make them rather rumpled and twisted with leaves going in all directions. The buds come out at the same angle that the leaves are facing; without any leaves pointing upward, you will only get branching going sideways. To build a good branch structure you want buds going upward that you can then wire down to create good movement and further refinement. If all the branching is sideways, the result is a fishbone pattern – flat and no upward growing branches to fill out the height of the pad of foliage.
Building the branches follows this sequence:
- Remove any old branches; while this can be done any time I find it easiest to decide about design in late winter or spring.
- Wait for new shoots to elongate at least 4 inches but as much as 12 inches depending on the size of the tree; thin to one per site, select for spacing, and position along the trunk.
- Wire the remaining shoot at each site and set bends into it. The angle of the branch coming from the trunk should be slightly upward and the first bend should be downward. Alternate up-down and side-side, not down-side, up-side to avoid corkscrew shapes.
- Allow the tip to grow unrestrained. Watch the wire to make sure it doesn’t dig in, and remove once the branch is set. If the wire digs and you take it off and the branch springs up, rewire it.
- Cut the branch back to roughly 1/3 the length of the finished branch; estimate based on what the silhouette should be.
- Wait until new shoots elongate to 4-5 inches before wiring and repeating the process.
- Once all secondary branching is set the process of wiring is mostly completed. Some of the new branching can be wired to add branching or replace branching that gets too coarse.
- Grow tertiary branching by shortening the growth cycle and by removing strong shoots in favor of weaker interior buds. The tertiary branching will normally not be wired as it is too small to easily do so. Control the growth in spring, allow to elongate somewhat in summer (trim the ends if getting more than 4-5 inches,) and then trim to silhouette in winter.
April: the branches already elongated as much as 12″ for the spring.
I tend to look through Kokufu albums and other Japanese show books as inspiration for how to style some trees. I sometimes find really good inspiration for Elms, but since they are not a particularly popular species with Japanese professionals, the styles I tend to see in the books have a very flat branching pattern. For this tree, my goal is to have a natural-looking elm branching pattern, similar to my Kifu Elm bonsai.
After some cleanup, removal of the shoots that were too strong, and wiring. Some of the branching is already past where I’ll want the silhouette to be, and there's quite a bit of development left to do in the crown section. I’ll likely remove the sacrifice at the end of the growing season if not before.