Answer: Moss or algae spread by spores and grow wherever environmental conditions are encouraging to it. You may find that removing the yews opens the area to enough light and air circulation that the moss or algae dies back on its own. Dampness also encourages moss/algae, so avoid watering the area as well. In some cases moss is seasonal, appearing in spring and then naturally disappearing in summer when the weather turns hotter and drier. Using a cleaning solution of bleach and water on the house (and possibly scrubbing with a brush but not power washing) should remove algae. Then rinse the area with plain water to further dilute the bleach. Make sure it is dry before the puppies are allowed to go there.
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