Name That Stain!

best roof moss cleaner

Unless you live in the middle of the desert, chances are you’ve had to deal with moss, algae, lichen, mold and mildew stains. Any outdoor surface where there is moisture and sunlight is vulnerable to these pesky growths, from walkways to decks, from the driveway to the pool.

But you don’t need a degree in biology to identify which type of growth you’re up against, and you don’t need caustic chemicals, a power washer or tons of elbow grease to make your property stain-free and beautiful. Just spray, and let Wet & Forget do the work for you!

“Fuzzy” green growth

If you see a thick, velvety, carpet-like growth on surfaces such as your roof, deck or concrete, moss is the culprit. Moss is a simple type of plant that can grow nearly anywhere.

While it doesn’t have “real” roots, moss has root-like structures that can do real damage to surfaces by causing pitting in wood, shingles, bricks and even glass. Moss can be a real disaster on your roof, where it can damage the surface of shingles and grow between the shingles and the roof’s surface, causing the shingles to separate and let in water.


Smooth green growth

A smooth, flat green growth that appears on your siding, driveway, porch or other areas is green algae. Algae is a simple organism that is related to plants.

Like plants, algae can use sunlight to make its own food. All algae needs to grow are sunlight, air and moisture. Algae’s versatility makes it able to grow just about anywhere, even on the side of a truck!

Not only is this growth ugly–algae can become very slippery, which makes it a hazard on walkways and roofs.


Black staining

Dark black streaks on your roof or black splotches on your sidewalk or siding are most likely due to black algae. Black algae is similar to green algae, but with the addition of a dark protective pigment.

This pigment gives black algae its color, and also serves as a sort of sunscreen to protect the algae from UV rays. This is why black algae is so common on rooftops, where it is exposed to many hours of direct sunlight.

Gray or white staining

Smooth gray or white stains on outdoor surfaces are usually a type of fungus. Fungus grows where there is moisture, can come in a wide variety of colors, and can have a “musty” smell.

We usually call these ugly fungal growths “mold” or “mildew.” No matter what you call them, these growths are a disgusting, unwelcome presence on your deck, patio or outdoor furniture.

Scaly material

If your deck, the side of your home, or other outdoor surfaces have a scaly-textured material growing on them, your problem is lichen. Lichen comes in nearly every color of the rainbow (see photo), but its scaly texture is what gives it away.

It is a complex combination of fungus and algae that have learned to live together, forming a unique growth. Lichen can cause pitting on outdoor surfaces and is a big problem in some cemeteries, where it makes headstones unreadable.

The symbiotic relationship between the fungus and algae makes lichen very hardy and difficult to get rid of. But don’t worry–even this tough growth is no match for Wet & Forget.

Clean Up with Wet & Forget!

No matter which of the above growths you’re up against, Wet & Forget will get rid of the ugly stains for you. No need to scrub–just spray once and walk away!

  • For moss, algae, mold or mildew:

Mix 1 part of the Wet & Forget Concentrate with 5 parts water in a pump-up garden sprayer. For high elevations or large surfaces, connect the Wet & Forget Xtreme Reach ™ Hose End product to your garden hose to apply.

Thoroughly saturate the area with the solution. Make sure to give the surface 4 to 5 hours to dry if there’s a threat of rain. If you’re spraying moss, be sure to soak the moss thoroughly so that the solution completely penetrates the growth.

  • For lichen:

Use a garden sprayer to thoroughly saturate the lichen with a solution of 1 part Wet & Forget and 5 parts water. Wait 15 minutes, and spray a second time.

This will allow the Wet & Forget to penetrate the lichen’s 2 layers. It is best to spray lichen on a day that is not too sunny, to prevent rapid evaporation and to allow Wet & Forget more time to work.

  • To clean outdoor furniture:

Stains in the fabric can be treated with a solution of 1 part Wet & Forget and 5 parts water. Allow drying. Before you use the furniture again, rinse it thoroughly with clean water.


  1. We have outdoor natural stone tile which has a sealer on it. The tile has calcium stain resulting from hard water leaking from planters. Will Wet & Forget remove the calcium stain? Will it also remove the “sealer” on the tile? Thank you.
    Frank and Trish Dolasinski

    1. Hi Frank and Trish,

      Wet & Forget only removes organic growth like moss, mold, mildew, and algae so if you apply to calcium stains you will not have any results. As far as your sealer, Wet & Forget will do no harm. Thanks for commenting.

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