Expert Tips for Removing Lawn Moss

The Trouble with Lawn Moss

lawn moss

All the scores of different algae, liverworts and mosses are collectively known as moss to the ordinary home gardener. They form on lawns, paths, walls, crazy paving, tops of pots, seed boxes, garden frames and even on woodwork.

Because these low growths are amongst the most primitive of all growing plants, they have a great capacity for survival and in remote ages played a big part in the formation of soil. They are flowerless plants and do not make seed, but they can be propagated by vegetative means, that is by division and spores. The latter are so tiny they are everywhere, up in the sky, thousands of feet down in mines and caves, in water, in everything we eat or breathe. Many of them have an affinity for anything that has been burned and my experience is that if mosses of various kinds are more widely disseminated than they used to be this may well come from the wider use of peat.

Through the ages peat deposits have been burned, either by natural visitations such as lightning, or more recently by man. Immediately following the burning, huge areas are covered with various types of mosses and liverworts (the moisture-loving sphagnum is not included in this category as this requires special conditions). Many upland areas drain into reservoirs and though harming no one, thousands of millions of spores are disseminated in tap water. There are also millions of spores blowing about in the atmosphere to take into account and these are responsible for the greening of soil in seed pans, boxes, pots and where the hose pipe is used on the lawn or flower beds. At some time most gardens have received peat of some sort or another and this too carries its quota of spores.

Is Moss Harmful?

How harmful then is moss on the surface of the soil?

Quite frankly, I think an awful lot of people worry unnecessarily about it. True, it is dangerous on paths and crazy paving because it makes them slippery. When raising slow-germinating seeds such as those of roses, the moss may inhibit the growth of the seedlings by smothering the soil and excluding the air and forming a mat which cannot be pierced by the seedlings. But under shrubs, roses and strong-growing herbaceous plants, I have not been able to find that it does any harm whatsoever.

The formation of moss will become more widespread following the use of chemical weedkiller, because I have found that mosses will re-establish themselves more quickly than the higher plants such as grasses and weeds. This, I  know, already worries a lot of people, but my own close observations have satisfied me that provided the soil is stirred at least once a year, moss will not seal the soil to exclude air or rainwater.

Topdressings of acid fertilisers also encourage the growth of mosses. In fact their very formation is an indication that the surface of the soil, at least, is rich in nitrogen.

Mosses on crazy paving can be eliminated by sprinkling with mercurised lawn sand and on concrete paths, drives, hard tennis courts by watering or spraying with an ordinary tar oil winter wash. Various proprietary bleaches, such as chloride of lime, will also remove dangerous and disfiguring mosses. However, care must be taken when using caustic materials as if they drain into vegetation, such as lawn edges or borders, they can cause harm. Damage can also be done to carpets by walking on treated paths and then going indoors.

Mosses on lawns are a separate problem and although one is repeatedly advised to examine the drainage, this is only one small part of the problem. Lawn moss can and does appear on the best drained lawns, depending on situation and environment. Bad drainage is often blamed for the appearance and growth of mosses. This, however, cannot be true of such situations as the sides of pots, the tops of stone walls, crazy paving and tree trunks where it often hangs in festoons. What is necessary for the formation of the majority of species of moss, is ample moisture in the atmosphere. This means that certain districts are more prone to moss formation than others. On the shores of Lough Erne in Ireland for example, I have seen moss 4 inches deep on concrete gun emplacements with the moss breaking up the surface of the concrete. It also breaks up roofing tiles and fills up gutters.

As a pioneer plant, it is extremely valuable as it adheres to rocks and, as just mentioned, unsightly lumps of concrete. It traps wind-blown soil and in the situation examined, formed the first home of such diverse plants as wild strawberries and primroses. Here is an extreme example of the growth of mosses on a well-drained surface – a fellow gardener in this district lined his driveway with moss-covered stones. Birds took the moss from these for their nests and the buds and spores settled on the asbestos roof tiles of his bungalow and in two years the resulting growth had dissolved and destroyed the whole roof.

Moss disseminates by division of minute detachable buds and by spores. Thus, the vigorous raking of lawns so often advised may spread more new plants than destroy old ones. Assuming that the lawn is reasonably well drained, that is, water does not stand on the surface for more than twenty four hours after a heavy downpour, it is more important to encourage the growth of grasses than to tear the lawn apart by raking. Forking or hollow tining, at least once every three years and annual top-dressings of sandy soil will do more good than severe raking. Certain acid peats as previously mentioned can  encourage moss. Heavy liming  is no cure either. In fact, as the best lawn grasses grow in slightly acid soil, liming will only encourage the production of the more leafy and stalky grasses.

Killing Lawn Moss

Early feeding, say at the middle or end of February, is one way of killing lawn moss as this encourages the early growth of the finer grasses. The coarser grasses, such as those grown by the farmer for cattle feed, start into growth some weeks later.

Various chemicals may be used for controlling moss, and perhaps the best of these is mercurised lawn sand which has the advantage of killing not only the moss and the small viable buds but destroys the  spores as well. This is best applied in April at the rate of about 3 oz per sq metre.

Where the moss is extremely dense it may be necessary to loosen and carefully rake some out, because when it is dead and in districts of high rainfall it tends to settle as a solid mass or film which excludes air. Air is absolutely essential to the roots of grass plants and the density of the moss growth will determine the severity of the treatment needed to overcome it.

It may take two or three years to eliminate dense lawn moss by forking, sanding and adding small amounts of line grass seed with the solid topdressing. I recommend adding 1/4 oz of seed to 2lb of a sand and soil mixture. A method used and recommended by the Turf Research Association is to make up a compost of a 6 inch layer of good loam, interspersed with 2 inches of farmyard manure and more soil. This is allowed to mature for twelve months and is then sliced down and sieved before applying.

Spent mushroom compost may be used, but this should be free from chalk lumps. In gardens where soil is difficult to come by the old soil knocked out of the pots of chrysanthemums and tomatoes may be used to advantage. Stack this for twelve months and then sieve it through a 1/4 inch sieve before using.

Generally a complete fertiliser, preferably organic based, is better for the promotion of good grass than large quantities of sulphate of ammonia which in time tends to kill out the liner grasses and encourage weeds. My own experience with fine lawns is that no violent action should be taken at any time. By this I mean making any application of large quantities of fertilisers, dressings or lime, with which to try and achieve a rapid change in soil and herbage conditions. The soil and herbage of a lawn should be in a state of equilibrium and it can easily be disturbed, thus the maintenance of a lawn is one of the trickiest jobs in gardening.

Playing surfaces and lawns used for the family to run or mess about on, can easily be compacted if used extensively when the surface is wet and sticky. This compaction of the surface forms an ideal place for the development of algae, which is the beginning of lawn moss formation. Raised bumps in the lawn or ridges which are scalped by the mower are also nursery beds for mosses which are then carried all over the lawn. Often these can be reduced by filling up the hollows on each side of the hump or, in extreme cases, removing the hump. All these are contributory causes to moss formation, and are points to be watched, but I feel there is no single cause for moss-grown lawns.

05. August 2010 by Dave Pinkney
Categories: Lawncare, Lawns | Tags: , , | Comments Off on Expert Tips for Removing Lawn Moss


Get every new post delivered to your Inbox

Join other followers: