In order to treat moss, it helps to understand a little about this complex and interesting plant.
Moss is believed to be one of the earliest plants known and there are approximately 20,000 species that have been identified throughout the world and it is believed to have evolved from algae within the oceans million of years ago.
As moss do not produce flowers / seeds they therefore have to reproduce through spores whereas the male plant has to fertilise the female eggs which will produce an embryo that gives rise to a spore-bearing structure known as a sporangium.
During this sexual stage the male sperm is transported by water droplets in order to reach the female egg. This explains why you don’t find moss in a totally arid environment and how next doors moss jumps over to your lawn.
Moss spores are simple single-celled structures which have the primarily purpose to colonise new ground.
Asexual reproduction of mosses occurs by the development of new shoots from the previous years growth or by fragmentation of the plant.
Depending upon the moss species, the plant will survive by acquiring nutrients from water droplets to extracting these from the soil or materials on which they are growing. Hence moss can be found on a wide variety of surfaces and not just lawns, flower plots, roads and pathways, brick walls and even artificial turf - in fact on pretty much anything as long as it has an anchorage, moisture, and some nutrients.
So for a plant that has survived a billion years it is no wonder that is can be every gardeners nightmare!
Moss in lawns will only gain establishment where the grass is weak and the ground lacks the required environment conditions to aid the grass sward and roots to remain actively strong.
Therefore a healthy well managed lawn will very rarely suffer a full blown invasion of moss.
Treating moss is fairly simple but this will not be a one off solution. You first need to understand why you have encountered an invasion.
Moss infestations are usually at their worst in the winter and early spring due to the higher than normal water table and plenty of surface moisture thus inefficient / inadequate drainage could be the primarily cause as could increase water retention caused by too much thatch in your lawn.
The first point of call would therefore be to take a soil core sample to examine the soil profile and if need be take the appropriate remedial action as part of your treatment program.
The same can apply to the opposite of having too much moisture where poor irrigation in drought conditions will have a negative effect on the grass swards health and allow moss to take hold. Under these conditions lawn care professional may recommend applying a wetting agent to aid the water to reach the grass roots more quickly and of course more longer term solutions.
Light or more importantly the lack of it will have a major impact on your grass health. You will be amazed at how effective pruning of offending shrubs and the removal / thinning of trees will have on the grass swards health and wellbeing. It is just a shame that the same can’t be said for dealing with buildings unless you treat these with special light reflecting coatings but being realistic this just isn’t going to happen!
Whereas correcting drainage, irrigation and light can be more of a challenge, providing the correct balance of nutrients is probably more practical. The key is to encourage strong growth to the grass roots and sward by a regular program of feeding and where applicable correcting soil deficiencies. Care should be taken when applying lawn feeds as if the wrong supplement is applied at the wrong time of year if can and will cause other turf diseases. Applying a high dose of nitrogen at the wrong time of year for example would encourage excessive top growth just when just when you don’t need it!
Ideally a soil sample should be taken to assess the soils acidity (a pH value around 5.5 will provide the optimum pH for most lawn grass species). A professional soil analysis will identify the soil make up and help assess what nutrients may be lacking or in excess. So unfortunately it isn’t always the case of popping along to your local garden centre for any old bag of feed and also be mindful of professionals who do not offer a soil sample before deciding upon what course of treatment is required.
I have lost count the number of times certain clients have asked me to mow their lawns to a point of scalping it. Mowing the grass too low (unless of course they are cultivars such as those used for bowling greens) will seriously affect the grass plants ability to survive. The grass sward will be forced to redirect its energy and nutrients away from the roots in order to produce new leaves, resulting in a weaker root system. And as there is insufficient leaf tissue surface it will be unable to effectively make food for itself through photosynthesis. Thus leaving the lawn open for weed and moss evasion.
I see more lawns that have been damaged by poor mowing practices than any other cause! If your lawn suffers from a “cushion habit moss”, this is usually a good sign that you are mowing the grass too short and you should increase the cut height.
Finally another area to consider as a possible cause of your moss invasion could be down to soil compaction. This is often caused by heavy foot or machinery traffic.
Soil compaction will seriously restrict the air movement through the soil and restrict good root penetration. It will limit the water penetration of the soil and restrict gaseous exchange and result in the build up of fibrous growth. All ideal conditions for moss and other lawn weeds to take procession.
Similarly to taking a soil analyst, a soil core sample should be taken to determine the soil profile and what particular course of action is required.
Compaction normally requires aeration – Don’t be fooled in to being sold hollow tine as the only method required – there are three types of aeration, Hollow Tine, Solid Tine and Flat-Bladed Slitting Tine.
Solid tine is normally used as a quick method of helping draining but care should be taken if “spiking” too many times and normally an alternative approach is often required else you may find that you are causing more compaction! Saying that spiking a lawn is perfectly acceptable if you know why you are doing it and gauge the results.
My personal favourite is slitting tine as this allows the greater intake of air and moisture. Furthermore it has an additional benefit by “pruning the grass root” and actively aiding new side shooting.
The hollow tine is the removal of 1,000’s of cores of soil and is mainly intended to relieve severe compaction and allowing to help change the soil structure for example brushing sand into heavy soil.
Whilst the major lawn care franchises will often only recommend hollow tine, if this operation is undertaken at the wrong time / conditions it can in fact cause further compaction. Personally I would only hollow tine my lawn once every three years if it was required.
You should therefore seriously question if your lawn care professional insists on yearly hollow tine – unless there is a particular justification you would have to question if profit is their motivation or simply lack of knowledge / experience. And please ensure that the cores are removed from the lawn afterwards - not all lawn care companies do!
So once the correct primary cause(s) of your moss infestation has been identified, you can now start to tackle the moss which is the easy part. However now days and mainly down to the EEC there are fewer chemicals available to do this. Thankfully the good old days of mercury-based moss killers are long gone but this only leaves two alternatives for controlling moss in turf. Jewel which is a selective herbicide spray from Scotts containing carfentrazone-ethyl and mecoprop-P that will control moss and also a range of broad-leaved weeds. The other product are those containing ferrous sulphate which are available as a ready-to-use liquid or fertilisers containing high levels of ferrous sulphate e.g. Scotts Greenmaster Mosskiller, and numerous brands of Lawn Sand.
It wouldn’t be sensible to suggest what chemical treatment should be used as this will be determined by the individual lawn and its overall condition. Furthermore depending upon what product you purchase and what method you use to apply it are all different.
There are also different schools of thought as to if you should treat the moss before scarifying / raking or afterwards. Personally I would always opt for treatment first to kill the moss and reduce the likelihood of re-infecting the lawn by fragmentation of the plant.
So once you have chemically treated the moss and given it sufficient time to do its job you have to rake the dead moss out (by hand or mechanically) and take the corrective action for its primary cause. This is the hard part and again I would suggest seeking professional help / advice. Not only will it be less painful on the body you may be pleasantly surprised at how cost effective it is.
Whilst small areas can be quickly re-seeded or indeed the whole lawn topdressed and over seeded, if you have a major infestation, don’t dismiss re-trufing the lawn. Not only will this give you an instant lawn, if the area is prepared properly it will address many of the primary causes of the infestation.
Once I have eradiated the moss, as part of my regular lawn maintenance program is to treat the grass with fairly regular light applications of sulphate of iron, not only does this help strengthen the sward and hardening against frost and disease, it will kill off any moss which may appear, an added bonus is that it will also help green up the grass. However be careful not to rely on this one treatment. You should regularly ensure your lawn has the correct balance of nutrients for the right time of the year. Again this is where your lawn care professional should be able to advise on the correct program of treatments.
And finally, if you are trying to control moss on hard surfaces be mindful that it is not always as effective as it can be on turf.
Surprisingly there are no longer any approved pesticides for hard surface moss control and remember any products containing ferrous sulphate will leave rust stains and shouldn’t be used! However, there are a number of specialist hard surface cleansers that will address the problem and I would personally use a chemical that addresses algae, moss and lichen.
As with turf, ideally you should try to address the primary cause such as by improving drainage to prevent flooding and by increasing the natural airflow.
There are many businesses on Landscape Juice that would be more than happy to offer their services to you or alternatively please don’t hesitate to contact me, our teams service most of the South of England and up to the Midlands.
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