How to Recognize, Remove, and Prevent Mold Outdoors

How to Recognize, Remove, and Prevent Mold Outdoors

Maybe you’ve noticed it: green moldy growths spreading across your roof, creeping along siding, or even appearing on pavers. The fact is that molds thrive in damp coastal areas like some parts of San Diego, but can be present wherever moisture collects. The problem is that once mold settles in or on a home, it can grow on nearly anything – wood, paint, sheetrock, you name it. Not to mention, the ongoing moisture and warm conditions in Southern California backyards often result in mold popping up on common outdoor surfaces such as patios, deck furniture, and outdoor cushions.

Enough mold can mar backyard landscapes, but the worst of it is that its spores can pose a health hazard. If you notice mold and mildew growing in your backyard, it’s important to quickly and effectively destroy it, and we’ll tell you how.

But first…

What is Mold?

Part of the fungi family, molds are microscopic organisms with enzymes that digest and decompose organic matter. They reproduce through spores like other fungis such as mushrooms, and yeast. The truth is, molds are horrible things: they “eat” fallen trees, dead animals and rotting fruit, but the problem begins when they also begin to “eat” areas around (and in) your home. Although there are thousands of different types of mold, they all need moisture in which to grow. Mildew is the same as mold, and it is commonly found in damp areas as well.

The most common household molds you may observe are blue-green and white, white, pink, grayish, fuzzy, and black. More scientifically, these molds are:

Alternaria —

Mainly found outside and in plant soil, alternaria is an airborne that settles on flat surfaces. Although it’s not as moisture-dependent as other molds, it thrives in moist areas and is often found in areas with sustained water damage from plumbing leaks and floods.

Alternaria presents with long hairs and a velvety texture. It ranges in color from dark olive to brown.  It’s been known to cause respiratory problems.

Aspergillus —

One of the most common molds, aspergillus is also one of the most allergenic. This fast-growing mold can form wherever there is high humidity and organic matter for the mold to consume such as in building materials, fallen leaves, and compost piles. Aspergillus is also commonly found on foods and in home air conditioning systems and ranges in color from blue-green to pinkish-red.

Cladosporium —

Commonly found outdoors, cladosporium loves any damp, dark environment. A black or green pepper-looking mold, cladosporium often grows on the back of toilets, and on painted surfaces. Although it is nontoxic, this mold still produces allergy symptoms, such as red and watery eyes, in humans. Cladosporium is an airborne mold, and is hard to eliminate completely.

Penicillium —

This mold is most often found on wet and dead organic matter outside. You might see its fuzzy green, white, or blue fuzz on spoiled or fallen fruit. Its spores can cause allergic reactions and other irritating symptoms.

Stachybotrys —

This is the airborne toxic black mold you most often hear about and want to avoid completely. Stachybotrys is a slimy black mold, and requires a lot of moisture so often thrives where there’s been water damage or excessive condensation. Although this mold isn’t as common as you might think, it produces volatile organic compounds (VOCs) and should be removed from the home in all cases.

What is Mold?

Removing Mold from Outdoor Surfaces

First and foremost, to fully eliminate mold, you must address any moisture problems, and then remove the mold.

Common causes of moisture pooling are poor yard drainage caused by ill-maintained gutters and drains and improper slope. If you have these issues, clean out gutters, fix drains and regrade your yard so it slopes at a rate of one inch per foot. Repair leaky pipes and roofs and check for water stains on all outdoor and exterior surfaces.

Once you’ve identified any areas of excess moisture and addressed them, get your gloves and dust mask on and prepare to get rid of any mold that’s collected.

Removing Mold from Outdoor Surfaces

Patio Surfaces —

If the surface can withstand it (note that high pressure can damage wood, brick, or mortar), power wash your patio with water using a wide, low-pressure nozzle or fan tip. You can also spray on oxygen bleach (check for color fastness) and let it soak in without drying. Scrub moldy areas with a stiff brush and rinse with water.  If you notice mold coming back, make sure water drains off your deck properly.

Building Materials —

If you’ve stored wood or other building materials outdoors and they are showing signs of mold, first seal off the area while wearing your rubber gloves and dust mask (or respirator if the mold is the toxic black variety). Create a makeshift airlock to isolate spores by covering the opening to the supply area with a sheet of plastic slit in the center, then cover that sheet with another. Wrap all materials twice and wash the remaining hard surfaces with a bleach solution and let dry.

Remember – first put on some rubber gloves and a dust mask. Now, mix a quart of chlorine bleach with 1/3 cup of dish detergent and three quarts of water. Use a sponge and scrub, scrub, scrub the mold. The detergent will help lift the mold and the bleach will kill mold spores that could bring the mold back. Rinse all cleaned surfaces with water from your hose. Dry what you can.

How to get rid of mold in your outdoor living space

Outdoor Cushions and Pillows —

Gloves and mask? Check. Now, use 3/4 cup of bleach to one gallon of water, take a sponge and wipe all fabric surfaces. If you’d rather and your cushions/pillows are washing-machine-friendly, throw ’em in with some laundry detergent and that 3/4 cup of bleach, and set a standard washing cycle.

Preventing Mold from Growing on Outdoor Surfaces

On the Lawn —

Let your grass dry and (wearing your gloves and mask) rake up any dead grass and/or thatch. Put these materials in a garbage bag. Put fungicide that’s safe for lawn use in a garden sprayer and apply it to moldy areas. Cut your grass to expose as much of its growth to light as possible. From now on, water in the morning, so the sun can evaporates what your lawn didn’t use.

Preventing Mold from Growing on Outdoor Surfaces

To keep mold from returning or to make your yard less “mold-friendly,” try the below:

— Mow and rake your lawn regularly

— Keep gutters clear to drain away from the house

— Trim plants away from siding and trees from roof so sunlight can find its way to these surfaces and kill mold

— Keep windows and siding caulked to prevent moisture from finding its way in

— Keep shingles and flashing maintained

— Promptly repair and seal leaky pipes and roofs

— Do yearly roof inspections to catch any issues before they bloom into mold infestations

— Clear leaves and debris from drainage areas around your home and yard

— Store firewood away from the house

— Use materials like treated lumber, stainless steel, galvanized fasteners, and stucco siding outdoors because they are commonly resistant to mildew

— Clean and dry water damaged upholstered furniture

— For initial small mold infiltrations, scrub surfaces with a mild detergent solution and then apply mixture of one-fourth cup bleach to one quart of water

Final Thoughts

Mold is a necessary part of the earth’s ecosystem, but when allowed to grow unchecked in our home environments, can cause problems such as health issues. It’s important to be aware of the areas where mold can form and minimize the moisture conditions so it can’t thrive. If you  find mold, cut off its moisture supply if you can and remove it completely. In serious cases, consult a professional to have the mold removed safely.

Have you had any problems with mold in your yard?

Photo credits: Houzz as captioned; and Morgue File (image URL: : Please note that we are not mold experts and this information is provided as information only and not recommendations. Consult professionals for expert advice.