Your lawn under a snow blanket
How does your lawn fare in winter, at temperatures of minus 20 degrees Celsius or lower, or under a blanket of snow? Don't worry! Most of the grass types and varieties used for lawns in Europe are completely frost-resistant, which means that they do not freeze.
Nevertheless, winter can be a challenging time for your lawn. Even under a protective layer of snow it can experience serious problems. Temperatures often drop to freezing or just below and it is therefore actually comparatively warm. As long as the snow is loose and porous, nothing much will happen to your lawn. However, if the snow stays around for a long time and, for instance, light rain often falls on the snow and freezes immediately, the snow becomes very tightly packed and an ice crust may form on the surface. This means less air in the snow layer, which in turn provides ideal conditions for the growth of certain types of fungi, such as snow mould (Fusarium sp.). The situation becomes difficult when the snow is walked upon, as even individual footsteps can remain visible as yellow patches well into the spring.
Your lawn does not go into hibernation like many animal species, although all life functions are significantly reduced. In other words, it hardly grows at all. This is what makes it so vulnerable to fungi, as it does not outgrow the resulting damage. What preventative measures can you take against fungal diseases? It is important to keep the lawn well fed in winter, but not to overfeed it. This means feeding it with potassium in particular in autumn, but to stop using nitrogen. A regularly mulched lawn experiences healthy nutritional growth that is balanced in winter. It is important to ensure that the last cut is carried out using a grass catcher box so that as little cutting residue as possible remains on the lawn, as this encourages the growth of fungi.
The lawn should not be cut too short heading into winter. Any leaves lying on the lawn should be removed as quickly as possible. Along with weather conditions, grass types and even varieties play an important role, as their susceptibility and resistance to fungal disease varies significantly. Some experts recommend clearing the snow from your lawn. In my opinion this is not advisable, as considerable mechanical damage can be done to the lawn and the formation of a thin, but compact layer of snow and ice is promoted.
Until around 25 years ago, basic slag was often scattered on snow-covered lawns in early spring to melt the snow faster. The dark grey, almost black colour of the inexpensive basic slag absorbed more heat from the sun and thus helped to melt the snow significantly faster. Because basic slag is also rich in phosphorous (approx. 15%) and other micronutrients such as iron, magnesium and manganese, lawns were also lightly fertilised at the same time. Basic slag is (was) a by-product of the steel industry for around 100 years and was the finely ground slag produced in the Bessemer process. Since the switch to other steel production methods, with iron ore, which is low in phosphates, now being used almost exclusively, basic slag is no longer available.
On that note, I hope that your lawn manages to cope well with the snowy winter.
Prof. Karl E. Schönthaler
VIKING garden expert