Is vermiculite biodegradable? Vermiculite does not break down or decompose when it’s used in potting soil. That means vermiculite is a permanent way to amend and improve your soil. Does vermiculite decompose? Vermiculite decomposes with time to release the plant nutrients potassium and magnesium. … Perlite does not furnish any nutrients to the plants. Its … Continue reading Is vermiculite biodegradable?