Why Your Siding Turns Green in Mississippi (And How to Get It Off)

If the north side of your house has a green film on it, you're in good company. Drive through any neighborhood in Southaven, Hernando, or Olive Branch and you'll see it on vinyl siding, brick, fences, and even the outside of gutters. It's not dirt, and it's not a sign you're a bad housekeeper. It's algae, and Mississippi is about the perfect place for it to grow.

What that green stuff actually is

Most of the green on siding is a type of algae, sometimes mixed with mildew and mold. Black spots and streaks are usually mildew. Fuzzy gray green patches on brick or fences can be lichen. All of them are living things that feed on the dust and pollen that settle on your house.

Why Mississippi homes get it so bad

Algae needs three things: moisture, shade, and warmth. North Mississippi provides all three for most of the year.

• Humidity. Our summers stay humid for months, and the morning dew keeps siding damp well into the day.
• Shade. Big oaks and pines are great for the electric bill and great for algae. Anything that keeps the sun off the wall keeps it wet longer.
• Long warm seasons. Growth slows in winter, but we have a lot of mild days where it keeps going.
• Pollen. Every spring the pollen coats everything and gives algae a meal.

Why the north side is always worse

The north side of a house gets the least direct sun, so it stays damp the longest after rain or dew. That's why you'll often see one side of the house perfectly white and the other side green. The same goes for any wall behind tall shrubs, under a deck, or near a downspout that overflows.

If the green is worst right under the roofline, take a look at your gutters too. Overflowing gutters soak the siding below every time it rains. Our post on signs your gutters are clogged explains what to look for.

Is it hurting anything?

Mostly it's cosmetic, but not completely. Algae holds moisture against the surface, and over years that can break down paint, stain wood trim, and make vinyl brittle. It also makes walkways and steps slippery. And it spreads, so a small patch this year is a whole wall in two.

How to get it off safely

The instinct is to grab a pressure washer and blast it. That usually makes things worse on siding. High pressure can force water behind vinyl panels, chip paint, and leave stripes where the wand passed. It also tends to remove only the top layer, so the green comes back fast.

The method that works is soft washing: a low pressure application of a cleaning solution that kills the algae and mildew, followed by a gentle rinse. We break down the difference in soft washing vs pressure washing.

If you want to try a small spot yourself

For a small patch you can reach from the ground, a soft brush and a siding cleaner from the hardware store will work. Wet nearby plants first, work from the bottom up so you don't get streaks, and rinse from the top down with a garden hose. Skip the ladder and skip the pressure washer.

How to slow it down after cleaning

• Trim back shrubs and branches so air and light reach the wall
• Keep gutters clean so they don't overflow onto the siding
• Point sprinklers away from the house
• Plan on a soft wash every one to two years

Get it handled

If your house is wearing a green coat, our house washing service takes it off without damaging your siding. We work all over Hernando and Southaven, and you can get a free quote just by texting us a photo.