|I have black streaks on my roof which, based on what I read, are algae. What can I clean it with that will be safe for the shrubs and flowers below? I've read that bleach and tsp work, but that sounds harmful. Any environmentally safe products?
|Answer from NGA
April 3, 2010
|Bleach does work to kill roof moss but overspray can harm plants unless it is rinsed off right away. Another product that's safe is Zinc sulphate. It kills moss in 3-4 days. It is available in powdered form so there's no concern about overspray, but the product will eventually dissolve in rainfall and run through the downspouts. It's also available in liquid form. For the most part is safe to use near your plants. I usually rinse my shrubs and perennials off with plain water after spraying the roof - just to make sure.
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