Scandinavian research shows better winter survival with impermeable covers on golf course putting greens

April 12, 2022

By Trygve S. Aamlid, Norwegian Institute for Bioeconomy Research 

9 people spreading a cover on turf at a golf course in the fall
Figure 1. Staff and golf course members covering greens in November at Asker GC, Norway.
Photo: James Bentley.

NIBIO, the Norwegian Institute of Bioeconomy Research, is honored to be an international collaborator in the WinterTurf project.  Winter stress management has for many years been one of four thematic areas prioritized by the Scandinavian Turfgrass and Environment Research Foundation (STERF), and we are currently half way through  the project ‘ICE-BREAKER:  Reducing the agronomic and economic impact of ice damage on golf courses and other grasslands.  For the NIBIO Turfgrass Group, the WinterTurf project is a continuation and extension of ICE BREAKER. Along with preliminary data from the two winters 2018-19 and 2019-20, the most impactful finding in ICE-BREAKER so far has been significantly better winter survival and improved start of the new season on greens covered with impermeable covers before winter.

In Norway and the four other countries, Iceland, Sweden, Finland and Denmark, that are collectively referred to as ‘the Nordic region’, access to fungicides for the prevention of Microdochim nivale, Typhula spp. and other winter-active diseases is very limited compared with the United States. Despite that, with the exception of Denmark and southern Sweden, superintendents in the Nordic region are more concerned about abiotic damages caused by ice and melting water than by snow molds (Kvalbein et al., 2017).  In 2018, a year with severe winter kill in the most densely populated area in southeast Norway, the average economic loss per 18-hole golf course was estimated to $45,000 (U.S.), or more than $4.5 million for the Norwegian golf industry as a whole.  

During this winter (2021-22), Nordic superintendents have again had sleepless nights as many golf courses in eastern Norway, central and northern Sweden and Finland have been under ice since early January. As of 25 March, the snow and ice has started to melt on most courses, and the superintendents that I have spoken with during the last couple of weeks seem to be a little more optimistic now, at least when it comes to survival of creeping bentgrass and fescue green. Winter damage will probably be more severe on the annual bluegrass greens which tend to dominate in Central and Northern Sweden.

Impermeable covers as a key to better winter survival

With data collection that began in 2018-19, results from four golf clubs around Oslo have demonstrated that the installation of impermeable covers shortly before the first snow fall in mid- to late November is a key to better winter survival in our region. While one of these golf courses has invested in durable and tailor-made Green Jacket covers from Canada, the others simply use a type of transparent, 115 µm thick and 24 m wide plastic sheets that are otherwise used in agriculture and the building industry (Figure 1).  Important preparations before coverage includes spraying at least twice with fungicides and that collars are dug into the foregreens to prevent water from seeping under the covers.  So far, most courses have also put out a permeable spring cover (e.g. Evergreen, NorGro or similar) as undercover under the plastic and installed a ventilation system made up of flat tubes and drainage pipes between the undercover and the plastic as insurance.

a rectangle-shaped research plot with wood edging. The turf in the plot is green with a few brown spots.
Figure 2. Frame surrounding main plots that had plastic under 10 cm layer of black ice for about 90 days.  Winter survival was excellent except for a few small patches of microdochium in creeping bentgrass (nearest subplot) and to a lesser extent in annual bluegrass (middle).  The most distant subplot is red fescue with impeccable winter survival.  The main plot to the left had ice directly on the grass. Photo: Marte Skattebu.

During the winter 2020-21, field trials at Apelsvoll, the most northern and continental of NIBIO’s two turfgrass research centers, showed clear advantages of the impermeable cover, not only on annual bluegrass, but also on red fescue and creeping bentgrass greens (Figure 2). During the winter of 2020-21, we compared the impact of a 10 cm layer of compact ice either directly on the grass vs. the same ice layer but with impermeable plastic between the ice and the turf. The trial clearly demonstrated the importance of the plastic sheet:  Winter survival was down to 10 % with ice directly on the grass vs. more than 80 % with plastic under the ice.  While part of the reason for this may be less hydration and freezing damage of turfgrass crowns, sensors placed in the thatch also showed higher O2 and lower CO2 levels with a plastic layer between the grass and the ice.

The ‘Ice & Plastic’ trial at Apelsvoll has been repeated this winter, but an update will have to wait for another blog post as this year’s trial is still under ice as of 25 March. However, based on the very convincing results from the previous year, superintendents at as many as 18 Norwegian golf courses covered one of more of their greens in November 2021. Needless to say, researchers and superintendents are very anxious to see the results over the next couple of weeks!


Kvalbein, A., Waalen, W.M., Bjornstad, L. & Aamlid, T.S. (2017). Winter injuries on golf greens in the Nordic countries: Survey of causes and economic consequences. International Turfgrass Society Research Journal 13(1): p. 604-609. doi: 10.2134/itsrj2016.09.0826