Keeping it Sweet

Excessive thatch on a lawn can be caused by over-acidity on the surface. Acid rain, ammonium fertilizers, ferrous sulphate, and breakdown of old dead material all contribute to acidity. Whilst a certain amount is necessary (pH 5.5 to pH 6.0), too much acidity restricts the activity of the micro-organisms which break down the old thatch materials; it is also conducive to moss.

For the first time, have spread about 35 grams of limestone flour per square metre (1 oz per square yard) on dry lawn surface. Hope this will help reduce thatch without raking (which destroys the turf and leaves it open to water loss).

Note: Lime must be in the form of ground limestone (calcium carbonate, not the stuff they put on walls and houses), the finer the better. Although slower acting (can take 2 or 3 years), this is the safest way. Must be careful not to add too much, as this could make lawn disease-prone. Could do with some more rain now, to help the breakdown process.

Will be interesting to see how much moss develops this autumn. I used to use 'growmore' granules (7-7-7), which contains a proportion of calcium carbonate. I never seemed to have a moss problem then. However, I have since discovered that this might be a cause of thatch, not a cure (because it contains too much phosphorus). Just when I think I've found a solution. . ..