Pinching Elms: a beginner's primer

by Andy Rutledge, USA

Pinching is the last technique in a sequence of operations used to develop an elm bonsai. It is the pinching technique that produces the outer layer of fine ramification. There is a right way and a right time to apply this technique to your bonsai and the information in this article should help beginners learn when and how to pinch back the foliage.

When to start pinching

It is not uncommon for bonsai enthusiasts just starting out to begin pinching shoots on elm bonsai either too early or late in the development of the branches. There is a perfectly understandable reason for this, for in order to properly develop elm branches we have to let the branches get a bit untidy and out of shape. Most of us want our bonsai to look "good" all the time, but this is not possible when properly forming the branches.

Don't pinch these shoots yet!

In the photograph above the foundation for a good branch structure is just beginning to emerge (image looking down on an undeveloped foliage pad). The primary and secondary branches are only 1 to 2 years old and the basic structure is not yet established. For now, just pinch the terminal shoots occasionally, but let the interior shoots grow freely until the end of the growing season.

First you cut…

When developing branches for elm bonsai you have to first let the main structure grow without pinching and then cut back late in the winter to establish the form. Early on in the branch development you should work to establish the larger branches and shoots and wire them for shape. They will hold up the outer, more ramified growth that will come in later years.

During this period, let primary branches grow unrestrained until they have the diameter that is close to what you will ultimately want. At the same time, let secondary branches grow in a similar manner. You will not pinch, but will cut back with scissors as necessary.

The image sequence below illustrates a typical example

Above: Here is a typical immature branch structure on a Chinese elm. It includes a number of actively growing terminals and some dormant buds.

Above: In late winter, cut back each of the existing shoots to an appropriate bud; one that is pointing in the correct direction for future growth. Don't trim the tiny shoot closest to the trunk. It first needs to grow larger.

Above: Let the new shoots grow unrestrained during the growing season. Shoots may grow longer than they appear in the illustration above. The appearance will be rather messy. That's okay, just let them grow. No pinching.

Above: In late winter, cut back each of the shoots to form a basic structure and wire the new shoots for shape. Here, the terminal shoot is left longer so that it will grow a bit larger than the others. In the coming growing season, pinch only the terminal shoots, but not the interior shoots. Don't pinch the terminal shoots too often - it's not yet time for that. Pinch perhaps twice during the season.

Above: Continue with this regimen for 3 or 4 years, leaving less of the new shoots with each late winter trimming. Now, with the structure pictured above, pinching can begin. In another year or two, the structure will be mature and very appealing.

…Then you pinch

When the underlying structure is complete, it is time to begin pinching in earnest. The purpose of pinching is to stimulate the dormant buds at the base of each leaf near the tip of the branch, and some buds further back as well.

This sequence of images illustrates how to properly pinch a Chinese elm (Ulmus parvifolia).

Here (above) we have a shoot that needs to be pinched. It has developed 7 or 8 leaves and the stem is still green and soft where we need to pinch.

Important first is to decide which direction you want the new shoot to grow. The last leaf you leave on the shoot points in the direction of the new shoot to come. Generally, you want the new shoot to grow toward an open area away from the trunk.

Grasp the portion of the shoot you will remove with your finger and thumb and gently pull. Do not pinch with your fingernails. If the shoot is already lignified and is so hard or strong that you have to try and cut with your nails, you should not pinch. In these cases get your trimming scissors and cut the shoot instead of pinching.

The tender young leaves and shoot should come off easily. Make sure to leave a bit of the shoot beyond the last leaf that remains. If you pinch too close to the remaining leaf you could damage the bud at its base.

In the image above, the shoot was pinched where the line indicates. While the terminal leaf buds have not yet sprouted, two dormant buds further back on the shoot have begun to grow. This is a very good thing: one shoot becomes three shoots and a more ramified structure results.

When you elm bonsai is developed to the point that you need to pinch, you must not let it grow too quickly and you must be diligent in your pinching. At this point you should fertilize less (perhaps half your normal regimen).

A mature elm bonsai needs daily attention during the growing season - or at least attention every other day. All of the shoots will be at different stages of development, meaning that you need to address the pinching needs almost daily for different areas on the tree. If you neglect pinching for a few days you may jeopardize the proper formation of the fine structure, inducing too-large shoots in the outer layer. Be diligent.

In the image above (January 2004), the elm is a bit out of balance in development. Portions of the structure are ready for constant pinching and other areas are not. In particular, the mid-level portions of the far right and left are still too undeveloped for an overall pinching program.

Here is the same tree the following spring (March 2004). In the areas highlighted above, the branches lack development. This year they will only be pinched a little bit on the tips of the main shoots. Next year they will be ready for the detail that continuous pinching will bring.

With proper care and technique it is very easy to develop highly ramified growth on elms, as in the photograph above. The key is in not starting to pinch too early in the development process of the branches. Once the underlying structure is well defined, the last layer of structure can be produced by an ongoing regimen of pinching the soft growth throughout the growing season.

Note that by pinching all through the growing season, you will have to do some "clean-up" trimming at the end of the season or the shoot tips will be overly clogged with tiny shoot. Be sure to thin those out or your bonsai will have knots on the ends of the fine shoots. If this happens, just cut them out of the structure and remake that area. Elms grow fast and this kind of repair is quickly accomplished.