Control Moss in the Lawn

Shade, clay soil and poor drainage all help moss grow in the lawn so try a few natural control techniques to get more grass

Okay, so you’ve got too much moss in your lawn. Or is it that you’ve not enough grass? More than likely it’s one and the same so what to do about it?

Start by assessing the environment and natural factors that may contribute to your lawn being thin or unhealthy and therefore creating ideal conditions for moss growth.

Once you’ve done that, make as many of the following environmental changes as you can that are relevant to your lawns situation. Though this is not going to make the moss disappear it is a natural way to tip the scales in favour of the grass.

Shady lawns are prone to moss

Problem: For shade read poor light. Grass, like all plants needs light to photosynthesise (manufacture food). If it’s not getting enough light it is not getting enough food. Quite often shady areas will have tall but sparse grass that can look quite green. The grass naturally thins to allow each plant more light. The problem is ‘a few thin grass plants do not make a lawn!’

Solution: Reduce the shade if possible. If this is from buildings, walls or fences there is little that can be done. If however, the shade is from plants or trees things can be done.

For trees: make sure branches are two metres above lawn level. If the canopy is dense consider thinning it. If the tree has a preservation order please start by talking to a tree surgeon.

Bushes, hedges and plants: All by their very nature are dense and you wouldn’t want to thin them. However, consider reducing the overhang into the lawn and reducing the height.

Raise your mowing height. This means the grass traps more sunlight and puts the moss in even more shade. If the grass becomes thin try over seeding thin areas every spring with Lawnsmith® SHADYGREEN lawn seed for shady damp areas and Lawnsmith® STAYGREEN grass seed for dry shady areas.

Moss likes clay and wet soils

Problem: Grass like any plant needs air around the roots. This can be limited in clay or compacted soils. This is not ideal for the grass and it can become stressed and weak. Growth will be slow, colour poor and it won’t take long for moss to show. In addition, wet soils are often cooler than dry soils and this also reduces grass vigour.

Solution: You may be able to improve the drainage, or at least increase drainage in the top 2″ just by hollow tining the lawn. It may need doing every autumn depending on your soil and local environment.

To further improve the drainage in heavy clays it requires the addition of sand or a sandy soil mixture. Unfortunately you usually need so much that it becomes impractical. Hollow tining (coring) and brushing sand into the holes will make very little difference as the depth and density of the holes is usually inadequate. Top dressing with sand is also not the answer as the sand is on top when you need it below the clay soil to have any draining effect!

If the clay content is so high the only way is to start from scratch and rotovate a suitable free draining mixture into you existing soil after removing your old turf.

For large lawns an alternative may be to install drainage pipes. You’ll need a specialist drainage contractor for this as it’s not just a matter of putting in a bit of hardcore and a few pipes!

For small lawns putting drainage (a soak away) in the border(s) alongside the worst water logging area(s) can reduce the problem considerably. Go as deep as you can for best results.

If the grass becomes thin due to excess water try over seeding with Lawnsmith® STAYGREEN grass seed. Though this seed is meant for dry and poor soils it tolerates extremes better than most grasses and may well be your best bet if you want grass!

Poor air circulation and heavy dew

Problem: Reduced air flow increases dew formation and delays its departure. This leaves the lawn permanently wet in spring or autumn. Wonderful for the moss but unhealthy for the lawn. It’s also a great environment for fungal diseases to attack and weaken your lawn still further.

Solution: If buildings and walls surround your lawn then not much can be done. If plantings prevent a breeze reaching your lawn then thin them a little particularly low down. Fences can also be a problem and if you plan to replace them use the variety that allows air to pass through them.

Dry areas and lawn edges

Problem: A thin soil layer, or contact with stone (patio or driveway) can cause rapid drying of the lawn edges in warm or sunny weather. The grass then goes dormant and or dies due to the dryness! This allows moss to move in as soon as any moisture is available.

Solution: You need to prevent these areas drying by adding a heat barrier or keeping them well watered. See Lawn Edging.

North facing lawns

Problem: These are usually wetter, cooler and shadier than other areas. This means grass growth is often slow but moss growth is vigorous.

Solution: Raise your mowing height. This means the grass traps more light and puts the moss in even more shade.

You may also have to over-seed these lawns every spring because your lawn is in permanent shade from mid-autumn to mid-spring. Try over-seeding with Lawnsmith® SHADYGREEN mixture next time you scarify or rake your lawn.

Acidic soil

Problem: Most moss seems to prefer acidic conditions. This is also true of many of the fine grass varieties but the coarser grasses generally do not favour acidic conditions. As most soils are between a pH of 5.5 and 7.5 this is rarely the cause of moss problems.

Solution: Anything below a pH of 5 needs to have lime added. It’s best to apply this as ground limestone or dolomitic limestone which is slow acting, easy to spread through a fertiliser spreader and will not burn the grass.

Rarer still is a pH over 8. If this is the case it will be hard to lower and keep the pH lowered. I suggest overseeding with rye and smooth stalked meadow grasses which will do reasonably well in this pH. Our Classic Grass Seed will do well in these conditions.

Adapt your Lawn

Some things you just have to live with, so rather than making life difficult go with the flow and adapt a little.

Wet climate: Choose grasses that will put up with more water than most. Rye grass and tall fescues work well. Try over-seeding with our SHADYGREEN or STAYGREEN mixtures next time you scarify or rake your lawn.

Excess Rainfall: Periodically this happens so as soon as things get back to normal, rake out and over-seed any dead lawn areas before the moss and weeds take over.

Cloudy cool summers: Great for moss and some fungal diseases such as red-thread. A ‘hardening’ dose or two of Green-Up Ferrous Sulphate in the autumn will harden the grass and check the extra moss brought on by the weather. The lawn will look spectacular as well.

Long hot summers: Can do great harm to lawns. Grass has a great capacity to survive drought but over extended periods and perhaps with use of the lawn continuing, the grass plants may not survive. Even if they do, the chances are that when the rains arrive the moss will get going before your grass revives! You can help by over-seeding the lawn once the weather cools a little and moisture returns – usually August/September time.