During the dog days of summer, putting green collars commonly show wear from environmental stress. Contrary to folklore, research indicates that collars display symptoms of dollar spot and some other turfgrass diseases because the microenvironment of a collar is more humid than that of a putting surface, which is maintained at a lower height of cut (HOC) and therefore has a denser surface.
With that said, mechanical stress from increased lightweight rolling has certainly exacerbated collar wear. Clearly, the numerous benefits of frequent rolling, as revealed by turfgrass research, are worth the extra attention that collars deserve. However, perfectionists see the glass as half-empty, so let’s examine methods to minimize collar wear caused by rolling.
Recommendations for promoting putting green collar density and health begin with the operator (or supervisor) of a sidewinder roller, who must consider practices that can eliminate spinning or slippage on the collar.
• Consider the position of the drive roller in respect to slopes. As much as possible, the drive roller should remain on the downhill side of a slope, pushing the roller upslope (as opposed to pulling the weight of the roller up a slope). This reduces spinning while changing directions on the collar, and it is also an important consideration when approaching a green on a slope.
• Particularly during times of increased environmental stress, the roller operator should slowly come to a complete stop (and pause) before changing directions.
• An increasing number of superintendents advocate stopping short of the collar and changing the direction of the roller on the putting surface. This practice violates past recommendations — that is, never change directions or turn on the putting surface with any piece of equipment. This newer practice supports the adage “never say never,” because a tighter HOC on stoloniferous grasses causes less stress from traffic than a higher HOC.
• Decreasing the HOC on collars can also reduce wear caused by rollers and perhaps minimize some environmental stress.
• When possible, a vibratory roller should be used after topdressing to help incorporate sand into the canopy. Research indicates that a single vibratory rolling after sand topdressing increases sand incorporation into the canopy by more than 50% on bentgrass putting surfaces and up to 80% on bermudagrass. This is important because added abrasion from sand on a spinning roller can increase damage to the collar’s leaf tissue.
• For those who do not own a vibratory roller that can be lifted before contact with the collar, it may be beneficial to change sidewinder roller direction in the rough when topdressing sand is still visible on the roller. This is done to minimize the abrasion caused by the sand.
• One superintendent told me he seeds perennial ryegrass into his bermudagrass collars when they show wear from rolling. This is not a good fit for all desirable species because of concerns with contamination, but, in a pinch, grass is better than bare ground.
• Use of mats and grates has increased, but there must be enough time and/or labor to accommodate the laying and movement of the mats.
• Avoid getting putting green plant growth regulator (PGR) applications on the surrounding collars. As the HOC of the turfgrass increases, the aboveground growth rate decreases, indicating that the collar has a slower growth rate and therefore slower recovery from stress than the putting surface. The effect of PGRs also lasts longer on grass with a higher HOC. If the same rate of PGRs must be applied to the putting surface and the collars, it is a good idea to increase the nitrogen rate on the collars to stimulate growth that is being minimized by the PGRs.
I thank Luke Paddle, assistant superintendent at Oakdale Golf and Country Club in Toronto, and my research technician, Aaron Hathaway, for their input. For those who want to look deeper into PGR growth, I suggest research by Bill Kreuser, Ph.D., at the University of Nebraska.
For those who are wondering why I did not mention bleach and starch — you should not have read this article.
Thomas A. Nikolai, Ph.D., the “Doctor of Green Speed,” is the turfgrass academic specialist at Michigan State University in East Lansing, Mich., and a frequent GCSAA educator.