Many bonsai lovers appreciate and find joy in working with deciduous trees. They offer year-long delight, with lush growth in spring and summer, vibrant autumn colors, and subtle beauty in the pattern of bare winter branches.
There is no more prized species of deciduous bonsai in Japan than Zelkova Serrata, or Japanese Gray Bark Elm. Their popularity has grown in the United States as well. Zelkova are often grown to be enjoyed in all their detail in winter.
Zelkova are generally easy to care for. They are deciduous trees in the Elm family (Ulmacae), with alternating leaves, one per node. They will back bud copiously and are well-adapted to root work. To develop Zelkova, allow new shoots to run to 5-8 leaves and then cut back to 1-2. As the tree’s silhouette fills out, keep shoots in check by pinching vigorous branches before they elongate too much.
Zelkova is one of our favorite species to grow as bonsai. Depending on the season, we offer bare root, potted starters, copse (basically a small stand-alone forest), and broom-style Zelkova bonsai.
In his personal collection, Eric has been working on this Zelkova forest for a few years. It’s close to looking like a forest [and not just a box full of twigs.] The forest was originally a seedling flat that Eric intended to make into small broom-style trees. But after a few months he decided to trim them back to be the start of a forest. The natural spacing and the way that the trees have grown together since they were seedlings lends to the genuine feeling.
Each May in Northern California Eric performs a cutback on the forest. There is always uneven growth among the trees. Some of them are barely starting to leaf out and others are already going strong. To maintain some balance and to ensure there's not too much shading of the lower growth in a forest planting. remove all the long shoots and thin everything out.
Balance the twigging on the stronger trees to ensure they don’t get too coarse while working on the ramification on the other trees. Don’t wait until all the trees have leafed out to begin this work. This will lead the twigs in those stronger trees to get too big. Working on the trees in a forest composition as they are each ready helps to create more balanced growth over time. The roots from the more vigorous trees don't overtake the weaker ones because they are being kept in check.
To avoid swelling at branch junctions, remove all the excess buds that occur where multiple branches already exist. This portion of the thinning can be time-consuming due to the need to analyze each branch junction.
After completing the thinning work, move on to the shorter trees and branches at the bottom of the composition. Look for the biggest leaves and begins with pruning those shoots as they are usually the stronger shoots. There is a lot of scissor work to be done with Zelkova forests!
Once the cutback is complete, Eric places the forest in the greenhouse for a few weeks. Even in spring and summer nighttime temperatures are cool in San Francisco; using the greenhouse helps the forest keep growing vigorously. If a greenhouse space is unavailable, keep the forest on a heat pad overnight. With this forest, Eric will work on the composition again later in the spring. The focus is on defoliating, either the entire forest, or just the upper half if the interior and lower growth need more time with more access to sunlight.
Whether it’s a forest or a single little broom, working with Zelkova means a lot of pinching and cutting back, especially in the spring. In hotter climates, Zelkova will need more frequent cutbacks throughout the year. We have a playlist with more than a dozen videos on Zelkova over on our Bonsaify YouTube channel, where you can watch this work in action!