What Happened to my Bentgrass Roots?
This summer has been hot and wet for most of the Midwest. Actually 2018 is on pace to be in the top five hottest years. Looking back, spring was characterized by hot weather too. May started off hot, with June and July having some extremely hot and humid days, but broken up to some degree by a cold front that brought relief. I can remember being at a July 4th celebration where the temperature and humidity was oppressive, yet in a couple of days when I attended a car show, the temperatures had dropped down into the 70s. This alternating weather pattern was short lived. From the middle of August until now (September 20) the temperatures have been in the high 80s or low 90s with high humidity and rainfall.
If we look at the impact that temperature and moisture have on creeping bentgrass root systems, as average soil temperatures rise above 70 degrees, root growth slows and begin to die. The rate of decline accelerates as average soil temperatures rise into the 80s. Addtionally, above average rainfall during the summer has resulted in temporary anaerobic soil conditions from the rainwater saturating the soil. The lack of soil oxygen, which is needed for root respiration, enhances root dieback or death.
Photo: September venting on a creeping bentgrass turf with minimal root system present. The lack of roots has resulted in the turf being ripped or rolled up from venting. Picture was taken in mid-September in the transition zone.
So what has this meant for creeping bentgrass root systems? With hot and wet conditions extending to the start of fall new root initiation or growth has not occurred. Which can be quite frustrating as superintendents begin the process of coring and/or venting. In several instances, coring has resulted in the bentgrass being rolled or torn up. This is due to the lack of roots.
Obviously, many superintendents halted their fall coring activities. Many superintendents are waiting for next week when it should cool off. However, I would like to throw out a cautionary note. Several courses I have visited literally have bentgrass turf with little root systems. Creeping bentgrass is one of the last cool season turfgrasses to get that “pop” or “blip” of root growth in the fall.
From studies we have conducted here at The Ohio State University intermittently over 20 years, we have found that creeping bentgrass root growth push occurs from mid-to-late October. Not to say root growth does not occur earlier but the pop occurs in the later part of October.
The good news is that the best of fall creeping bentgrass root growth is ahead of us, and the bad news is that it is still ahead of us. So be patient and keep monitoring root growth ether with probes or “testing” out the turf with coring equipment. From a management perspective, stick with – and keep your faith in – the fall management programs that you have developed.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: