The cooler temperatures and forecasts for snow showers quickly bring the reality of winter preparations to mind. One of those preparations for many northern golf courses involves covering greens to protect the annual bluegrass from crown hydration and cold temperature injury. The cover systems usually consist of an impermeable cover placed over the green complex either with or without insulation. The concept behind the use of covers is to try to prevent plant hydration during winter and early spring, and to maintain a fairly constant temperature at or just below freezing. In a perfect world, the covers are placed over the greens in late fall after the final topdressing and fungicide applications are complete and the ground is partially or near frozen. We then keep our fingers crossed for a layer of snow and some seasonably cold temperatures through winter.

The need to add insulation under the covers is a question we often receive. The insulation may be in the form of a foam material or rigid plastic mesh that provides some air space to buffer the more severe temperature swings. Straw and bubble tarps are used for insulation on more northern golf courses where temperatures can drop well below freezing. A heavy insulation layer is probably not necessary if you are in an area where a deep snow pack is dependable or winter temperatures are more moderate. A thin insulating material that creates an air space will be helpful where snow cover is less dependable and low temperatures are not so severe. The thicker layers of insulation are a good idea in areas where permanent snow cover is questionable and below zero temperatures are likely.

The color of a cover also impacts the temperatures at the surface of the greens. White-colored covers have grown in popularity in areas where the greens are likely to be exposed. They reflect the sun and help to keep temperatures below the covers more stable. This is less of a concern further north where the snow is more dependable and a heavier insulation layer is in place.

The use of covers does not always guarantee success! Water can still find its way under the covers and hydrate plants leaving them vulnerable to injury.  Under the right conditions, turf can suffocate under impermeable cover systems. This usually occurs on more poorly drained greens, but also is a concern when heavy layers of snow and ice lie for extended periods above covers on unfrozen ground.

Covering systems need to be monitored and managed from the point of installation until they are removed in spring. That includes monitoring temperatures below the covers, checking for anoxic conditions (lack of oxygen), and having the ability to remove the impermeable cover and or vent greens when necessary. Only cover the amount of area that you can manage! Winter staffing needs to be available to do that effectively.

Cover systems for greens have evolved and do work to protect annual bluegrass and bentgrass from our ever challenging winter weather. The protection systems are not an exact science and have to be tailored for specific site conditions. When used properly, they provide a management tool that can make the difference between winter success or failure. Feel free to contact your Green Section office if you have any questions or concerns regarding the selection, installation, and management of winter covers.

Contact Dave Oatis, Director doatis@usga.org ; Adam Moeller, Agronomist amoeller@usga.org ; or Jim Skorulski, Senior Agronomist jskorulski@usga.org for a Turf Advisory Service visit this season.