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How to Control Moss in Lawns

The 2018 drought has caused a moss invasion in many lawns across the UK, which needs addressing this year.

During one of the driest summers on record, with temperatures reaching a scorching 35C in some parts, grasses really struggled to cope, resulting in damage to lawns across the country. While well established grass is fairly hardy and will recover, open, patchy areas in swards caused by the dry conditions, allowed moss to invade.  

There are many other reasons for the occurrence of moss, apart from drought. Water logging, acidic soil, lack of vigour in an established lawn, poor site preparation and mowing too close can all result in moss appearing.

Whatever the cause, moss can be difficult to eradicate completely from a lawn, since it reproduces from spores which enable it to colonise open areas quickly.

However, there are a number of ways to control moss:


  1. Scarification: Depending on the size of the lawn, a lawn scarifier or spring tine rake can be used to clear the area. Mowing the lawn before scarifying will make it easier to remove the moss. Don’t be too forceful, as you don’t want to rip out the existing grasses.  


  1. Apply iron sulphate to the moss, leave for approximately 2-3 weeks or until the moss begins to blacken, then either scarify or rake the dead moss out. If the moss is particularly dense you can scarify or rake the area then add the iron sulphate which will help to thin the moss and allow for better penetration.

Whichever method is used, it is important to note that these controls are temporary; unless the sward is improved the moss will return. Over-seeding is a good way of closing up the gaps that the moss has left behind, and adding fertiliser to the sward once the new seedlings are established will help to boost growth.

To overseed, harrow or rake the area to create a tilth, broadcast the seed over the area then rake in to work the seed into the ground. Walk over the area so you get a good soil to seed contact. Top soil can be added to help cover the new seed. Once sown, flatten the area. This is usually done by either treading in by foot or going over the area with a roller (depending on the size of the area).

Mowing the sward once the new seedlings are well established (approximately 3-4 inches) will encourage the grasses to tiller out and thicken, helping to close up the gaps and minimise the risk of the moss returning. Mowing will also help to control any annual weeds that germinate having disturbed the seedbed. Do not cut too short as this will stress the plants and you risk scalping the lawn, leaving bare patches for moss to infiltrate once again.

Date Posted: 6th March 2019