All about Algae

All about Algae

Ever wonder what causes those ugly green stains on your deck? How about those black streaks on your roof?

If you see green stains, black or brownish/reddish stains on outdoor surfaces around your home, chances are good that uninvited algae have taken up residence.

Algae staining isn’t always just a cosmetic issue. Algae growth on a surface such as a deck or walkway will make the surface very slippery and cause a fall hazard for you, your family and guests.

You don’t have to take it lying down, though. Read on to learn more about the “enemy,” and how to use Wet & Forget Outdoor to rid your outdoor surfaces of algae infestation.

What is Algae, Anyway?

The algae are a very large and diverse group of simple organisms. What these organisms all have in common is photosynthesis–the ability to use light to make food, like plants do–and a need for lots of water.

Many types of algae, such as the green varieties, are related to plants but lack stems, leaves or true roots. Algae is present in the soil sends its spores into the air; the wind deposits the spores on your deck, roof or other places around your property.

Algae thrives where there is plenty of water and not much direct sunlight, such as north-facing walls.

If you have black streaks on your roof, they are probably caused by a type of algae called gloeocapsa magma. Gloeocapsa magma is a type of cyanobacterium that can survive harsh sun, wind and cold because of its tough outer capsule and dark pigment.

The pigment makes gloeocapsa magma hardy enough to thrive in places that would be too sunny for other algae, such as rooftops. Gloeocapsa magma’s protective pigment is what causes those ugly black or brown stains on your roof, walls or other outdoor surfaces.

If you have green gunk on your deck or the north side of your home, it’s probably due to either cholophyta algae (“green algae”) or a cyanobacterium related to gloeocapsa magma. The green color comes from chlorophyll, the same substance that makes plants green.

To learn more about these green and black stains, check out this article.


Zap Algae with Wet & Forget Outdoor

No matter which type of algae is infesting your outdoor surfaces, Wet & Forget Outdoor is the perfect choice to remove the mess. Wet & Forget does the work for you, and won’t damage your siding or roof like pressure-washing can or rust your downspouts and kill your lawn like bleach does.

All you need to do is spray once and let Wet & Forget take care of the green stains for you.

For small areas, we recommend using the Wet & Forget Concentrate. Just fill a garden sprayer with 1 part Wet & Forget and 5 parts water, saturate the area well, and watch the algae gradually fade over time until it disappears.

For particularly severe algae stains, you can increase the concentration of the Wet & Forget solution. For high elevations and large surfaces, we recommend using the Wet & Forget Hose End product. Simply attach the product to your hose and spray your roof, siding, or driveway with Wet & Forget.

Be sure to allow Wet & Forget 4 to 5 hours to dry before there is any chance of rain. Hardy gloeocapsa magma’s tough outer sheath may cause it to take longer than green algae to disappear completely–have patience!

Wet & Forget’s gradual process gets the job done. Most people reapply Wet & Forget again 12 to 18 months after the first application to keep algae from gaining a new foothold.

Now that Wet & Forget has taken care of your algae problem, you’re ready to enjoy your outdoor spaces. Fire up the grill!

Remember: Algae can be very slippery. Be careful, especially on the roof.

Stop by our website to learn more about our easy solutions to everyday problems, so you can spend less time cleaning and more time enjoying life!


  1. John

    It kills roof algae?

    1. Teresa Fugatt

      Yes, Wet & Forget will eliminate roof algae. Just add 5 parts water and 1 part Wet & Forget in a garden pump up sprayer. Then fully saturate the roof and forget it! You don’t have to rinse, scrub or powerwash. Wet & Forget will work with the wind and rain over the next few months to clean the roof for you.