Bicarbonate of Soda: A cheap way to stop moss in the garden

If you have a garden, you’ll know the pattern: as soon as the weather turns wet, cool and gloomy, moss seems to appear everywhere - on the lawn, between paving stones, and across the patio. Many of the old go-to products have disappeared from sale or picked up a questionable reputation. That’s why more and more people are looking past the DIY shop and into the kitchen cupboard instead - towards a powder that costs next to nothing and can halt moss surprisingly reliably.

Why moss takes over your lawn so quickly

Moss isn’t a sign you’ve been lazy; it’s usually a clue that something isn’t right in the soil. It thrives where grass struggles. Common triggers include:

• acidic soil with a pH value below 6
• compacted ground where water drains poorly
• shady spots with limited sunshine
• consistently damp conditions
• a patchy lawn after drought or mowing at the wrong height

As soon as the grass thins out, moss moves in. It spreads like a mat, holding onto light and moisture and sapping the remaining strength from the grass. If you simply rake off the green layer, you haven’t solved what caused it. The soil is still compacted, wet and acidic - an open invitation for the next carpet of moss.

A slippery hazard: moss on paths and the patio

On paths, steps and patios, moss is more than an eyesore - it can be a genuine safety issue. In joints between paving stones, in cracks and on slightly textured surfaces, it creates a slick film. When it’s wet, a driveway can turn into a green ice rink overnight.

Heavy-duty chemical treatments are largely off-limits for private gardens. Legal requirements place tight restrictions on synthetic pesticides in gardens, on balconies and on patios. As a result, many older “moss killers” vanished from the shelves. At the same time, plenty of people prefer not to use harsh products around their home - out of concern for soil health, groundwater, pets and children.

"This is exactly where a remedy comes in that almost everyone has at home: sodium hydrogen carbonate, better known as baking soda or household bicarbonate of soda."

The kitchen powder that dries moss out

Household bicarbonate of soda is the fine, white powder often used for baking, cleaning, or neutralising odours. In the garden, it works against moss in two ways:

• it raises the pH locally on the plant’s surface
• it draws moisture out of moss cushions

The result is that the moss’s delicate cells dry out and die. Over the days following treatment, the colour shifts from rich green to a yellowy brown. That’s the point when it’s time to reach for the rake.

How to use bicarbonate of soda on the lawn properly

On lawn areas you need to be more careful than on stone, because grass reacts far more sensitively. A tried-and-tested mix for many gardens is:

• 2 to 3 tablespoons of bicarbonate of soda
• to around 1 litre of water

Step-by-step approach:

• Aim only for clearly visible moss patches - don’t soak the entire lawn.
• Pour the solution into a spray bottle or a pump sprayer.
• Apply on a dry day, with no rain forecast for the next 24 to 48 hours.
• Spray finely and evenly over the moss cushions.

After two to three days, you should see discolouration. That’s when the rake comes in: pull out the dead material thoroughly. The gaps left behind are ideal for a light overseed with lawn seed, helping grass fill the bare spots faster before moss can return.

"Create a small test patch: on strongly acidic soils, grass is more sensitive. If you’re unsure, try the mix first on an area roughly the size of an A4 sheet."

Paths and patio: bicarbonate of soda straight into the joints

On paving, concrete slabs or stone steps, you can be a bit bolder because there are no grass roots to damage. Two standard methods are commonly used.

Option 1: Apply dry

This approach is particularly effective for joints and narrow gaps in paved paths.

• Sweep the surface thoroughly, removing leaves and loose moss.
• Sprinkle a thin line of bicarbonate of soda along the joints - around 20 grams per running metre of joint is a rough guide.
• Work it in with a stiff brush so the powder drops into the gaps.
• Dew and light rainfall do the rest: the powder dissolves gradually and acts directly on the moss.

After a few days to a few weeks, the growth discolours and becomes easier to remove. Often, firm brushing is enough; for thicker patches, a joint scraper can help.

Option 2: Wet application for heavy growth

If the surface is already extremely slippery, a liquid application can be better - much like on the lawn:

• mix 2 to 3 tablespoons of bicarbonate of soda per litre of water
• use a watering can (without a rose) or a pump sprayer to apply precisely to affected areas

Depending on the temperature, leave the area alone for one to two days. Afterwards, rinse with a little water and brush off the dead material. If you have pets, keep them away from the damp patches during this time so they don’t lick the alkaline solution unnecessarily.

How often can you treat - and what are the limits?

Sodium hydrogen carbonate is relatively mild, but it isn’t a “pour it on and forget it” product. Specialists advise treating the same area no more than once or twice a year. If you sprinkle or spray far more often, joints can leach over time and lawns may start to yellow.

"Too much bicarbonate of soda can leave joints almost sterile - moss disappears, but small soil organisms and other plants can suffer too."

It’s also important to think about the wider garden. Water carrying dissolved bicarbonate of soda shouldn’t be allowed to run unchecked into vegetable beds, perennial borders, or a pond. Ideally, choose a day without strong wind and without heavy rain. If you’re working on a slope, boards or small earth ridges can help stop the solution flowing away uncontrollably.

Slowing moss long-term: soil care beats constant spraying

Bicarbonate of soda is a handy quick fix, but it can’t replace proper, underlying care. If you want less moss over the long term, you need to change the conditions it enjoys. Effective countermeasures for lawns include:

• Regular scarifying in spring and autumn to remove thatch and old plant debris.
• Aerating the soil, for example with a spiked lawn roller or dedicated aeration shoes.
• Improving drainage if water sits on the surface for a long time.
• Liming if the pH value is clearly below 6 (only after a soil test).
• Correct mowing height: avoid cutting too short so the lawn develops stronger roots.

On paths, a different tactic helps: create joints that leave little fine substrate for moss to take hold in - for example by using bound jointing compounds or ensuring the stones are tightly laid. If you want to avoid “green joints”, it’s worth considering whether the jointing material should be changed after removing the moss.

When bicarbonate of soda is not a good idea

Despite the benefits, there are situations where it’s better to skip it:

• right next to a garden pond or stream
• very close to sensitive ornamental plants
• on areas regularly used barefoot by small children
• where the joints contain stones or metals that are highly salt-sensitive

If you’re uncertain, test a small, inconspicuous corner and watch what happens over a few days. That way you can avoid unpleasant surprises.

Why bicarbonate of soda beats many “miracle cures”

This kitchen powder has one major advantage: you can be fairly sure what you’re using. Unlike dubious “organic miracle” products sold online, sodium hydrogen carbonate is a familiar product that has been used for decades. With water and carbon dioxide, it breaks down into less problematic components and degrades comparatively quickly.

With a bit of reading, you can adjust the dosage to suit your own conditions rather than relying on marketing claims. Combined with solid soil care, more air and light for the lawn, and a few practical tweaks around the driveway, you can reduce moss pressure significantly - without harsh chemicals, without high costs, and using a helper that’s already in the kitchen cupboard.