I have a couple of Bonsai trees (Zelkova Schneidria)
which are starting to show a white powder-like substance
around the lower part of the trunk. I am not sure if this is
an indication that the tree is unhealthy , or merely a harmless
lichen. It is possible to scrape the substance off, but
generally
it re-appears. Any advice? The tree is indoors, in a mostly
unheated room of the house where the termperature is around
2-8 C.

It probably is a calcium deposit from minerals in your water
supply. Unsightly but not dangerous.

Usually this occurs when you water your trees by submerging them,
pots and all in water. That's not the preferred way to water;
you should water from the top -- like rain.

And, Zelkova is NOT an indoor tree. It should be outside all
year -- perhaps with a little winter protection in locals with
bitter winters. Zelkova will not thrive and will eventually die
indoors.

I don't know what a "Schneidria" is, but just add that MOST trees
do better outside when weather permits.

Jim Lewis - - Tallahassee, FL - Our life is
frittered away by detail . . . . Simplify! Simplify. -- Henry
David Thoreau - Walden

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