The satsuki azalea community decided long ago what their preferred top dressing would be – mountain moss.
Also known as yamagoke (“mountain moss” in Japanese), this moss is typically harvested in China and packaged in Japan.
It can be used interchangeably with white sphagnum moss, but there are three benefits that make it popular for species like azalea that require a top dressing year round: it stays in place when it dries out, it re-wets easily, and satsuki roots like to grow into it.
An additional benefit that both mountain moss and white sphagnum moss offer is that they have a slight acidifying effect on the water. As a simple test, I added water to a bowl of mountain moss and after one minute the pH dropped from 6.7 to 5.7.
Dry mountain moss
Wet mountain moss
Although not all azalea growers use mountain moss as a top dressing, all of the ones that I’m familiar with use either mountain moss or white sphagnum moss. This is because unlike other temperate bonsai, azaleas can suffer significant root damage after wilting just one time. And if an azalea wilts several times during the growing season, there is a good chance it will be harder to keep the tree healthy until the roots recover.
I apply a fresh layer of moss to my azaleas in spring and spruce up trees that need it throughout the growing season. Here’s what the process looks like.
Satsuki azalea – much of the top dressing has washed away
The first step is removing the top layer of moss and soil. I can do this with bent nose tweezers or chopsticks.
Removing the surface soil
Top dressing removed
Once the old soil and moss have been cleared away, I apply a layer of mountain moss and press it firmly into place.
Mountain moss top dressing
Exposed root azalea – Hikari-no-tsukasa, 17″
After a few months, I can expect green moss to start growing on top of the mountain moss.
Moss starting to grow
In some cases, I get more moss than I need.
Thick green moss
That wraps up the mini-series on watering and top dressings for now. It’s back to bonsai work for the next post!
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