Tree saw dust
Can you use fresh saw dust on your garden for mulch?
Montgomery County Maryland
Depends on how fresh.
If the sawdust is from a live tree, alcohols will be evaporating from it immediately after it is cut, and these fumes can damage plant tissue exposed to them. If the sawdust is from a long dead tree or lumber, this will not be the case.
Because sawdust particles are so small, they decompose fairly quickly. The decomposition process uses nitrogen and, to some degree, uses nitrogen in the soil, which means the nitrogen is not available to the plants being mulched by the sawdust. This can be countered by sprinkling some nitrogen fertilizer on the sawdust.
You might not want to use the sawdust from black walnut trees, as these trees have a toxin which can injure other plants.