Why is my patio going green? The most common causes, plus expert fixes

Discover the reasons your patio is turning an unsightly shade of green, and what you can do to resolve the issue

multi-level patio at rear of large house
(Image credit: Perry Mastrovito/Getty Images)

If your patio is placed in the shade, or you live in a region with high rainfall and humidity, you will likely encounter a green patio at some point. This problem is not only a major eyesore when you want to be sitting outdoors and enjoying your yard, but it can also a dangerous slipping hazard in wet weather.

Luckily, there are several ways to fix a green patio, from satisfying pressure washing to natural removal products like vinegar. All of them will require a little elbow grease to work properly, but it will be worth the effort. 

Once your patio is clean again, be sure to implement some preventative measures to keep it pristine year-round.

moss on patio

Green growth can accumulate on patios in shady spots or after prolonged periods of wet weather

(Image credit: Zigzag Mountain Art/Alamy Stock Photo)

Why is my patio going green?

Patios turn green (and a range of other interesting colors) due to the growth of mold, moss, algae and mildew. These organisms all grow in dark and moist areas, making green patios particularly common in shady areas and during rainy seasons.

Although this green sheen is not always damaging to your patio, it does make the area look untidy. This growth can also become a slipping hazard – not ideal for those who use their patios often. 

Quick removal and regular maintenance are a key backyard cleaning task to stop the problem from getting out of hand and becoming even more difficult to remove.

Methods for fixing a green patio

There are several methods you can try to fix a green patio, depending on your space and what you have to hand. Try combining multiple methods over time for a long-lasting green-free patio. 

1. Use a pressure washer

Pressure washing is one of the first methods homeowners consider to remove the problem, and it can be effective for getting rid of moss from a patio. If you’ve ever seen any of those viral pressure washing videos, you’ll know why. A strong enough stream of water shows visible improvement almost instantly, quickly removing the growth from your patio.

However, there are a few downsides, as Mike from Atlas Ceramics points out. ‘What happens with power washers is that it leaves streaks and you can damage the grout. If you’ve got stone that’s sensitive, it can start to dislodge and get water underneath.’

Beth Murton, Head of Gardens for Homes & Gardens offers a word of warning too. 'Make sure you don't hold the nozzle too close to your patio materials as it can damage them,' she explains. 'The difficulty is that a lot of moss, mold and algae can accumulate in between the pavers, but if you fire a powerful jet of water directly into these you also run the risk of dislodging the sand between the joints or removing any sealant.' 

Bruce Alan, a YouTuber and garden tool expert, explains that pressure washing creates mess and needs to be done carefully too. ‘If you use a pressure washer, all that disgusting muck has to be pushed somewhere. I use a battery-powered blower to push the water into the lawn.'

If you have a large patio, pressure washing is certainly quicker than scrubbing each section individually, but it needs to be done as carefully and tidily as possible. If you want to play it safe, however, there are some effective ways to clean patio pavers without a pressure washer too. 

Headshot of Beth Murton
Beth Murton

Beth has been writing about homes and gardens for over 20 years, contributing to a number of leading magazines, including Real Homes, 4Homes, Period Living and Grand Designs. In 2020, Beth took on the role of launch Editor in Chief of Gardeningetc.com, a website dedicated to gardening and outdoor living. At the start of 2023, she moved to Homes & Gardens as the Head of Gardens, bringing her passion and knowledge for all things outdoors to our team.

pressure washing a patio

A pressure washer can be a quick way to remove green growth from a patio 

(Image credit: Ros Crosland/Alamy Stock Photo)

2. Use cleaning products

There are many cleaning products on the market designed to kill moss and algae, removing any green layers and in some cases, preventing new growth from forming.

Wet & Forget, available from Amazon, is one of the most well-known, but there are several others to choose from, such as BioAdvanced 2-In-1 Moss and Algae Killer and Cleaner, also from Amazon. Both products contain no bleach, making them safer for use in your outdoor space without killing grass, plants or animals.

Each product will come with its own instructions for dilution and application. For example, some can be sprayed on directly with a garden sprayer, while others need to be diluted first. The application method also depends on the area being treated and what tools are easiest to use for the highest effectiveness.

To avoid a potential patio cleaning mistake, first confirm the cleaner is safe to use on your patio area. Alan recommends testing it first, saying ‘as with any cleaner, you’ll want to test it in an inconspicuous area first following the instructions.’ 

cleaning a patio with soapy water and a broom

Using patio cleaning products and a stiff bristled broom will remove unsightly marks from your patio

(Image credit: kb79/Getty Images)

3. Try natural solutions

If you’re looking for a simple solution to get rid of a green patio using products commonly found around your home, many homeowners use white vinegar. The acidity of the vinegar kills the algae, allowing you to scrub it off to remove any patches of green. The vinegar needs to soak into the surface for a while to work. After about an hour, the algae should be easy to remove.

Although bleach is another recommended home product useful for removing algae, mold and mildew on patios, it can be harmful to the environment. Cleaning with vinegar is much safer and delivers similar results.

How to stop a patio going green

Preventing algae, mildew and mold growth on your patio is a much better long-term solution than treating it every time the issue arises. As Alan explains, ‘the best solution for preventing or mitigating moss is to increase sunlight in shady areas and correct any drainage issues.’

Unfortunately, that is not always possible, depending on your backyard landscaping and the position of your patio. In these cases, clean the patio thoroughly and practice regular maintenance by removing any growth as soon as it appears. Be extra vigilant after rainy periods when growth is more vigorous. The same rules apply for cleaning a deck

If you have a patio made from pavers, you can also fill in any gaps with polymeric sand after cleaning to stop moss from growing through the gaps. Polymeric sand (available from Amazon) can often be durable enough to withstand force from pressure washing too.


How can I get rid of algae from a patio naturally?

Vinegar is an effective natural cleaner that can remove green algae, mold and mildew from your patio. It's even possible to remove the likes of ivy with vinegar too. 

Simply spray the vinegar onto the surface of your patio and leave to settle before scrubbing or washing off the growth. Apply a second round if needed.

Neglecting your outdoor cleaning tasks is a common patio mistake that can lead to your paved space turning green due to an increase in mold, moss or algae, especially during the wetter months of the year. 

Although getting rid of it doesn't have to be as time consuming as you might think, remember that prevention is always better than cure, so regular cleaning should ensure you keep on top of any problems and stop them from getting out of hand. 

Madison Moulton
Contributing Editor, Gardens

Madison is a garden writer and editor, covering all things outdoors and lifestyle. After completing a BA in History and Political Science, she transformed her years-long passion for plants into a career writing for both digital and print publications. As garden editor of several print titles, Madison focuses on trends and developments in the continuously expanding gardening industry. When not typing away at her desk, she tends to her ever-growing houseplant collection and travels frequently, photographing and reporting on gardens around the world.