How to protect your greenhouse from hail damage

Hail often occurs as a side effect of so-called supercell thunderstorms. Only these extreme weather phenomena, which consist of several individual thunderstorms, heavy rainfall and numerous updrafts and downdrafts, can produce hail. Raindrops from the updraft freeze at high altitudes, then fall back down and grow as more frozen water droplets accumulate. Hailstones usually have a diameter of 0.5 to 3 cm and can weigh up to 20 grams. However, much larger hailstones can also occur, although they rarely fall as precipitation in our latitudes. Hail can occur at any time of the year, although an increased frequency can be observed in the months from May to August. Although hail can occur anywhere, certain regions are affected much more frequently than others.

• You can use hail zone maps, such as those from the German Federal Office of Civil Protection and Disaster Assistance (“Bundesamt für Bevölkerungsschutz und Katastrophenhilfe” – BKK), to find out about the local hazard risk.

Over the last 20 years, hail events in Germany have had devastating effects on horticulture businesses. The most serious events were in 2008, 2011 and 2013. Even though there has been comparatively less hail damage to Gartenbau-Versicherung member businesses in recent years, studies show that the frequency and intensity of hail events could increase due to climate change.

It is difficult to prepare for hail events at short notice, as they occur without warning. It is therefore particularly important to prevent damage in the long term. When planning a greenhouse system, for example, the use of safety glass is recommended. This has an increased resistance to breakage compared to conventional greenhouse glass. In the event of damage, it disintegrates into small crumbs of glass and therefore causes less damage to crops and greenhouse equipment. In greenhouse systems, care should also be taken to ensure that drainage channels are kept clean, as hailstones can otherwise easily lead to blockages and water accumulation. You should therefore regularly clear gutters of leaves and other debris so that water can drain away better. When purchasing solar and photovoltaic systems, also look out for hail-proof products. For outdoor crops such as nursery plants, hail protection nets can be used.