Answer: The moss is growing because of the shade and excess moisture the ivy is causing. Thin the ivy out to allow more sunshine and good air circulation and the moss will die off. To remove the stains on the block wall, a good scrubbing with diluted Simple Green or a 1-10 bleach solution should work. Be sure to rinse the area well with plain water after scrubbing to remove any residue.
Best wishes with your garden!
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