Mulching should only be done when there is active micro life in the soil. That means that the temperature in the surface layer of your soil should be at least 6 degrees Celsius. If mulching is done regularly when the grass is not growing, for instance during the warm summer months or late in the autumn if you live where seasons change, there will be little or no decomposition. Consequently there will be a greater risk of thatch development.
Grass remains contain 80 to 85% water, which makes it decompose quickly with low risk of causing thatch, unlike other dead plant remains. 如果每次只切掉草叶长度的三分之一，残留草的分解速度将会最快。 However, no more than half of the length of the blade should ever be cut, as this would increase the risk of dehydration due to loss of fluid in the plant.
Keep in mind that mulching cannot altogether replace the traditional collection of leaves. Therefore, it’s a good idea to collect the remaining leaves after the last mowing of the season, when the ground temperature is below 6 degrees Celsius and the grass has stopped growing. Otherwise the risk of problems like fungal attacks increases during the winter.