Zelkova are fun! I started a group about ten years ago, planted in my garden on a tile.
Trucks/roots are fused by now. Takes time! In your rock your trees will probably not grow fast and big enough to fuse!
Have fun with your project!
Quick update. Pines aren't doiing well.
I repotted two in a small bonsai pot. The buds were about 4 cm long, little under two inches. Then we had -15 degrees (celsius). Buds didn't grow anymore. Late June I pruned th buds as if I was candle cutting. On one of these two there are new buds...
This is a small larch. After three years in a small showpot and presented in our club show,
I potted this tree in a somewhat bigger pot to regain strength, spring 2020. It hardly grew last year.
Now it seems to be really taking off!
The new leaves of this young Hawthorn are suddenly turning black. Can this be because of a couple of frosts in the night or is it something else. It's just this one. Don't see this on my other Hawthorns.
Others are doing better. Although growthrate is so low that I will definitely go for mame size trees.
I'll be repotting them in small bonsaipots soon, and let them grow for 3 years, the remainder of our competition.