Zelkova serrata (Japanese Grey Bark Elm) are a deciduous tree with smooth bark and delicate branching that are prized in bonsai for their winter silhouettes. They are typically grown as broom-style trees from small to medium size; and rarely into large bonsai. Zelkova are also particularly well-suited to creating small bonsai forests, bonsai copse, and bonsai clumps.
We we've received so many questions about how to grow Zelkova that we decided to pull the answers altogether into this article because the techniques used to grow Zelkova from seedlings to small mature bonsai are dissimilar to many other deciduous trees. Zelkova are best grown in a slow and methodical manner, avoiding large chops and cuts so as to create smooth branch transitions and no scarring.
How to Start a Bonsai Broom
To establish broom-style trees, the single trunk trees are cut back in their first growing season after the trunk reaches about 1/16-1/8" thickness. This first cut is to establish a V low in the trunk and also what will become the final height of the tree. Essentially, the bottom of the V - the point where you make the first cut - should be about 1/3 the height of the finished tree. If you want a tree that is 12" tall, you should have about 4" below the V, keeping in mind that the middle 4" will contain most of the structure and the outer and upper 4 inches will be all fine branching.
Once the basic structure is established, allow the tree to repeatedly grow out and cut back to two leaves. Thin any areas where multiple branches occur to avoid swelling. Select branching that angles upward properly and eliminate branches that have odd angles. In Japan, many growers clump young zelkova twigs together using raffia in winter to train them without the use of wire; this make the twigs more uniform in direction. But the wrapping material must be removed before the trees begin to leaf out.
How to Start a Bonsai Forest
A good bonsai forest has many subtle qualities and your eye knows when they are all in place. We have created copse and forests from three to over fifty trees in one container. Start with a variety of young trees and separate them into 4-5 size categories. The 2-5 largest trees will be the focus of the forest; think of the smaller ones as complementary and mostly to create branching and widen the scope of the forest. You can pair a couple of the larger trees near each other. Focus on "dis-ordered order" - using wire you can create small clumps of trees in mixes of the three smaller sizes, or just medium or small trees.
Place the largest trees first, and then use the clumps of smaller trees to complement them. Strategically leave some empty spaces while grouping trees together in other areas.
FAQ: Frequently Asked Questions About Bare Root Zelkova
Q: How should I protect Zelkova trees until repotting time?
A: The bare root should be "heeled-in" to a soil mix loosely - we use 80% perlite and 20% coco coir, but bonsai soils or even potting soils work perfectly well. Keep them protected from freezing temperatures, ideally maintaining them in the range of 34-40F until repotting time. This can be done in a cold frame, a garage, a refrigerator, or a greenhouse if you have one. Monitor the humidity and soil moisture as you would during the growing season, keeping them damp but not soaking wet.
Q: Should I put bare root Zelkova in an organic potting mix to promote more root division?
A: There are many soils that will work fine, but we prefer 70-80% perlite with 20-30% coco coir. Akadama mixes work well, and young trees can grow in standard nursery soil mixes before being transitioned later into bonsai soil.
Q: Can I plant bare root Zelkova as soon as I receive them?
A: You can do root work and create forests or broom starters in winter as long as you protect the roots from cold temperatures until spring. A bottom heat mat warming the roots can help after repotting, but keep the tree around 40F to ensure it remains dormant. If the trees begin to leaf before your weather is warm enough, ensure they receive adequate light and do not freeze.
Q: Are Zelkova a good candidate for clump style bonsai?
A: If you mean a small forest then yes - they do quite nicely as forests. If you mean a Kabudachi clump style with fused bases and multiple trunks - we have never seen Zelkova in that configuration but give it a try! If you mean more like a raft-clump (sinuous style is another term for this), it could be done without much difficulty, but it's not common.
Q: I saw your YouTube Video "Making a Bonsai Forest from Bare Root Zelkova (ASMR)". How many trees do I need to make a similar forest?
A: We used about 25 trees in the ASMR Zelkova Video.
Q: Do you sell the rocks in the video?
A: No, we would encourage you to explore collecting rocks from your local environment (with permission where needed!)
Q: I want to make a bigger forest, do you have larger trees available?
A: No, we would recommend that you use the bare-root we are selling, and then grow them into a larger composition. It can take 5-10 years to create, but the composition will be much better if the trees are grown together as a forest.
Q: What bonsai soil did you use in your video?
A: We used 1:1:1 Akadama pumice and lava sifted to a fine size. We also used a small amount of "Muck" when setting the rocks. Muck is a mixture of shredded sphagnum moss and the fine siftings of Akadama and can also contain clay.
For soil purchases we recommend BonsaiTonight.com.
Q: How can I find moss for my bonsai?
A: We applied locally collected wild moss. Look for moss that grows in the sun, not shade, and avoid moss that climbs trees as this can take over a small planting quickly. The smaller and tighter the texture of the moss, the better. You can grow your own moss by shredding some wild moss, mixing it with sand and shredded sphagnum, and adding a fine later to the surface of your pot. You can also apply the mixture to a flat containing just sand or fine soil. Be sure to keep it well watered (and use rain water, or low-mineral content water as moss doesn't like high pH water or high mineral content.)
Post photos of your Zelkova bonsai forest, copse, broom, or clump and tag us! On Instagram and Facebook: @bonsaifyonline. On TikTok: @bonsaify. Let us know how the process worked for you - post a comment to this article.