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Chinese Elm - Potential Mold / Pruning Tips

Hi Everyone,

I got my first Bonzai tree (Chinese Elm) at Christmas and have been gradually reading up on how to take care of it. I am wanting pointers on two points:

1) I am concerned about a green moss / mold that is growing on the surface. I don't know if this is good or bad - keep or remove? Please see pictures for further information:

And zoomed in:

Apologise if the images aren't entirely focused. I can try to retake if it helps?

The soil feels damp if I dig down a little, and try not to overwater. However, when I do I give it a good drink so that water is emptying into the water tray.

2) Pruning / shaping. I want to train the branch on the upper right as per picture below:

I haven't done any wiring before so not exactly sure how to go about doing this. Any general tips would be great! Can I use any grade wire or will certain ones damage the tree? The branch is roughly 4mm wide.

Following on from this, when I have pruned some of the branches they seem to be struggling to create new shoots - with any existing shoots dieing and drying out. Any tips how to encourage new shoots to grow again? This has mainly only happened on the branch in the bottom left as per the picture above.

Thanks for any advise in advance, and apologies if these are common questions!

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Super Green Thumb
Posts: 5122
Joined: Wed Jul 05, 2006 12:17 am
Location: Western PA USDA Zone 6A


The moss indicates that the soil is staying damp. Search the forum for something referred to as 'the chopstick method'

Since you have this in the indoor section I assume you are keeping this indoors. Slow, weak growth is probably due to low light conditions. Most of our homes are too dim to sustain good growth inside. If you are unable, or unwilling, to grow this as an outdoor tree supplemental lighting is pretty much a necessity.

I would forgo any attempts at training until you are seeing better growth. Re-potting is also in its future.


Super Green Thumb
Posts: 2661
Joined: Sun Apr 10, 2011 2:52 am
Location: SE-OH USA Zone 6-A

The roots of modern plant designations grew out of 18th & 19th century clerics, who started with the doctrine of signatures.

Things growing closest to the earth were the least divine, and thinga that were tall (or better yet flew) were the most exalted.

All that lowly green stuff is moss. It signifies that your soil is at least slightly acidic (likely good).

In the teaspoon sized biome of a bonsai pot anything that gets in the way of air penetrating soil after watering, makes it harder to tell when your trees needs are met.

Can you poke through moss (with your chopstick) and check that way? Um, yes sorta. Will it (the moss) bestir itself at night and kill the ivy plant when your not looking? Probably not.

It (the moss) is just in the way...

Worry about pruning and wiring after you've got more tree.

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