Moss in Lawns, When, Why, How? PDF Print E-mail

Mosses belong to a group of flowerless plants know as the Bryophyta which, in plant classification, comes between Algae and Ferns.  They have a relatively simple structure and reproduce vegetatively and also by means of spores. Mosses compete with turf for light, nutrients and, in certain conditions, can become completely dominant.

There are about 600 species of mosses in the British Isles, but only a few are prevalent in lawns.  The different species thrive under a range of conditions and it is often not possible to attribute their presence to any one factor.

MAIN CAUSES OF MOSS INFESTATION

  • 1.  Poor drainage leading to lack of aeration possibly caused by excessive compaction.
  • 2.  Excessive shade.
  • 3.  Shallow soil or low fertility.
  • 4.  Over acidic soil.
  • 5.  Too close cutting or wear due to over use.
  • 6.  Thick fibrous turf ‘mat’ (thatch).

CONTROL

  • 1.  Identify and try to eliminate the main cause of the infestation.
  • 2.  Rake out the moss.  Although moss can be spread in this way, the treatment should allow the grass to grow more vigorously.  The preferable method is to kill the moss with chemicals before raking.
  • 3.  Chemical treatment - Chemicals should only be used by competent users according to the manufacturer’s recommendations:

Ferrous Sulphate (also know as iron sulphate or sulphate of iron):

Traditional lawn sand usually contains ferrous sulphate together with ammonium sulphate and is a good moss killer.

Lawn sand should be applied in spring at the rate of 4-6 ounces per square yard (150-200 grams per square metre).

Note: The green cushion growth of the weed Pearlwort is often mistaken for moss. This plant will eventually produce small white flowers and requires a different control to that of moss.