How to Remove Moss from Garden Furniture

You bought that garden furniture with visions of lazy summer afternoons. Cold drinks, good company, maybe a book. What you didn’t picture was the furniture turning green and slimy the moment you left it outside for a few months.

Welcome to the reality of outdoor furniture in the UK. Our damp climate means moss and algae treat your garden bench like a five-star hotel. The good news is that cleaning it off isn’t difficult once you know the right approach for your furniture type.

Why Garden Furniture Gets So Green

Garden furniture suffers from the same problems as patios and paths, just in a more concentrated form. It sits outside in all weathers, often in shaded spots, and provides plenty of texture for moss and algae to grip onto.

Wooden furniture is particularly vulnerable. The grain provides endless tiny crevices for spores to settle into, and wood holds moisture longer than other materials. Leave a wooden bench under a tree for a winter and you’ll barely recognise it come spring.

Plastic and resin furniture gets algae more than moss. The surface is too smooth for moss to get a proper grip, but that green slimy film of algae will coat anything that stays damp.

Metal furniture tends to fare better, but it’s not immune. Algae will grow on any surface that stays wet, and moss can establish itself in joints, corners, and textured areas.

Cleaning Wooden Garden Furniture

Wood needs a gentler approach than hard surfaces like patios or concrete. You want to remove the moss without damaging the timber or stripping away any protective finish.

Start by brushing off any loose moss and debris with a stiff brush. Don’t use a wire brush on wood as it will scratch the surface. A stiff bristle hand brush or yard broom works well.

For the remaining growth, you have two options:

The soap and water method works for light coverage. Mix warm water with a squirt of washing up liquid and scrub the furniture with a brush. Rinse thoroughly afterwards. This is gentle on the wood but only removes surface growth. It won’t kill moss at the root or prevent regrowth.

A moss killer treatment is more effective for heavier growth or if you want lasting results. Apply it to the furniture, leave it to work for a week or two, then brush off the dead moss. The treatment continues working after application, helping to prevent regrowth.

Avoid pressure washers on wooden furniture. The high pressure can damage the wood grain, raise the fibres, and force water deep into the timber where it causes rot. If you must use a pressure washer, keep it on the lowest setting and maintain distance.

Once clean, consider applying a wood treatment or furniture oil. This helps protect the timber and makes it harder for moss to establish next time.

Cleaning Plastic and Resin Furniture

Plastic furniture is more forgiving than wood. You can scrub harder without worrying about damage, and the smooth surface means growth doesn’t penetrate as deeply.

For white plastic that’s turned green, a solution of warm water and washing up liquid will shift most of the algae. Use a sponge or soft brush and scrub the entire surface. For stubborn staining, a paste of bicarbonate of soda can help lift discolouration.

Bleach solutions work well on white plastic but use with caution. Dilute it heavily (one part bleach to ten parts water) and rinse thoroughly afterwards. Don’t use bleach on coloured plastic as it may cause fading.

For textured plastic surfaces like rattan-effect furniture, algae gets into all the grooves and is harder to shift. A moss and algae treatment sprayed on and left to work will penetrate these textures better than scrubbing alone.

Resin furniture can usually be cleaned with the same methods as plastic. Check the manufacturer’s guidance if you’re unsure about specific cleaning products.

Cleaning Metal Garden Furniture

Metal furniture, whether aluminium, steel, or wrought iron, handles cleaning well but has its own considerations.

Aluminium is naturally resistant to moss and algae because it doesn’t hold moisture the way wood does. A wipe down with soapy water usually does the job. Avoid abrasive cleaners that might scratch the finish.

Painted steel and wrought iron can rust if the paint gets damaged, so avoid wire brushes and harsh scrubbing. Clean with warm soapy water and check for any chips in the paintwork. Touch up bare metal to prevent rust.

Cast iron garden furniture is tough but heavy. Clean it in place rather than trying to move it, and make sure it’s thoroughly dry afterwards to prevent rust in joints and crevices.

Cushions and Fabric

Don’t forget the soft furnishings. Outdoor cushions and fabric covers can develop mould and mildew (which are different from moss but equally unpleasant).

Remove cushion covers and wash them according to the care label. Most can go in the washing machine on a cool cycle. For non-removable covers, scrub with warm soapy water and allow to dry completely in the sun.

Mildew on fabric often appears as black spots with a musty smell. A solution of white vinegar and water can help kill mildew spores. Spray on, leave for an hour, then wash off.

Store cushions indoors or in a dry storage box when not in use. Leaving them out in wet weather is asking for mould problems.

Preventing Regrowth

Cleaning your furniture is only half the battle. Without prevention, you’ll be doing it again in a few months.

Location matters enormously. Furniture in deep shade stays damp longer and grows moss faster. If possible, position furniture where it gets some sun, especially morning sun that dries off overnight moisture.

Covers help if you use them properly. A breathable furniture cover keeps rain off while allowing moisture to escape. Plastic covers that trap moisture make the problem worse, not better.

Regular cleaning prevents buildup. A quick wipe down every few weeks during the growing season stops moss and algae establishing. It’s much easier than tackling heavy growth once a year.

Preventative treatment works on furniture just as it does on decking and fencing. A light application of moss killer in early spring and again in autumn keeps growth at bay.

When to Replace Rather Than Clean

Sometimes furniture is beyond saving. Wooden furniture that’s rotting, metal furniture with extensive rust, or plastic that’s become brittle from UV damage may not be worth the cleaning effort.

Check for structural integrity before you start. Wobbly joints, cracked timber, or corroded metal mean the furniture might be unsafe regardless of how clean it looks.

For borderline cases, consider whether the cleaning effort is worth it compared to the cost of replacement. A basic plastic chair might cost less than the time and products needed to restore it.

Our complete guide to dealing with moss problems covers treatment approaches for all outdoor surfaces, not just furniture.