Turf News: Green Speeds
12 JUL 2023
Why Do Green Speeds Fluctuate?
For members, guest, and superintendent alike, it can be one of the most frustrating questions we encounter through the playing season. “Why can’t those darn greens roll the same speed everyday?!”
The truth is there are a multitude of reasons for constantly fluctuating green speeds. However, the main culprits tend to be the weather and essential cultural practices that must be performed to maintain the long-term health of the putting greens.
Let’s examine these two main culprits below.
Weather
- Rain. This is likely the most obvious reason. As we have discussed in the past, firmness is the main driver of fast greens and rain fall is an uncontrollable metric. Sometimes you get a little and things do not change too much, and sometimes you get a lot. To put things in perspective a 10 mm rainfall can slow your greens down by as much as 1-1.5 feet on the stimpmeter, and speeds will not return until the excess moisture evaporates or drains away. Repeat, back-to-back rain falls can have an even greater impact. The key for superintendents is trying to manage the moisture with the use of surfactants, maintaining drainage and keeping up with essential cultural practices. But most times we must wait for things to dry out.
- Temperature. This may seem like an unlikely culprit, but temperature is a major factor in maintaining green speeds for the simple fact that temperature controls the growth rate in plants. We all appreciate that grass is constantly growing, however the rate of growth can be less obvious to us. Turf grows vigorously when soil temperatures are between 16⁰C and 24⁰C. When soil temperatures soar above 27⁰C then growth is effectively shut down. On the other end of the spectrum when soil temperatures are below 12⁰C turf will not grow as well. When turf is exposed to temperatures below 12⁰C and above 27⁰C the plant is effectively under stress and the leaf blades tend to thin out providing less friction on the ball, translating to faster green speeds. When turf is within the optimal growth temperature range, plants are more vigorous, leaf blades become wider translating to more friction and slower speeds. This phenomenon can be most frustrating in the middle of the summer. Consider a typical summer week with no rain fall and nothing but sunshine. It may look something like this:
Mon: 28⁰C
Tues: 29⁰C
Wed: 27⁰C
Thurs: 24⁰C
Fri: 25⁰C
Sat: 27⁰C
Sun: 28⁰C
Considering the points just made we could postulate that growth would be slower on the Monday and Tuesday. Maybe a moderate rate of growth on the Wednesday. Vigorous growth on the Thursday and Friday and again no growth on the Saturday and Sunday. So yes, we did double cut and roll for men’s night, however the temperature was the main factor in this scenario.
- Humidity. In my estimation, this is the least talked about and most underappreciated factor to green speed fluctuation. Humidity can greatly affect ball roll. Low humidity understandably leaves the leaf blades drier, which in turn translates to less friction. High humidity can make greens ‘sticky’ and can slow things down or worse, give the player the perception of slow greens. When I work with the PGA Tour, they have a saying for this phenomenon, and we call the greens ‘sticky fast’. This means that based on the stimpmeter we have achieved our desired speeds, however when one observes the ball roll it does not behave as expected. The ball rolls off the putter and just abruptly stops, instead of gradually slowing down and then trailing off to one side or the other in the last 2” of roll. Consider the humidity in your first few putts on the practice green, and kindly appreciate that this varies greatly day to day which will either affect the greens speed or at a minimum our perception of it.
Cultural Practices
1. Topdressing. Is a double-edged sword. In the long run it undoubtedly aides’ superintendents in providing faster, truer surfaces, however in the short-term following an application it slows things down. The problem is that when we broadcast sand onto a putting green, we inevitably must work the sand into the canopy. Typically, this is achieved with a drag brush or drag mat. What then happens is as the sand is matted in and the turf is in turn stood up increasing friction during ball roll. It takes a few days after a moderate topdressing to cut off all the stood-up plants. Compounding this issue is the sands impact on our mowers. The sand can typically take 1-3 days to work completely into the canopy. During that time when we mow our greens the sand moves through our reel mowers effectively dulling our mowers and giving us a poor quality of cut on the greens. This will not be remedied until the sand is completely integrated and mowers can be sharpened.
2. Grain control. We deploy various practices to control grain on our putting greens which must be performed through the entire season to maintain dense, true, consistent surfaces, and to control grain. These include vertical mowing and grooming with brushes to name a couple. The outcome of performing one of these practices is the same as brushing in topdressing sand. Although, these practices can contribute to faster greens in the long run, for the first few days after implementation greens can play slower.
3. Pest control products, fertilizers, and soil amendments. As superintendents we have a multitude of products in our arsenal to aid us with managing our playing surfaces. Some of these products are applied to the leaf blades and some most be applied to the root zones. Whether it be an insecticide, a fertilizer, or a soil amendment, the only way we can get these products to where they need to be is by watering them in. Many times, the amount of water we required enough to soften the greens to the point where speeds begin to slow down.
Remember, if greens were rolling great over the weekend and suddenly have lost a foot or two in ball roll on Monday, it may not be neglect on your superintendents’ part, just simply us performing essential practices that are required to maintain speeds in the long run. Or perhaps the weather is the culprit. As we have learned, it’s not just rain that can slow things down. Or even worse it is one of a hundred combinations of the six points listed above and the many more that we did not have time to discuss. Whatever the reason for the day-to-day change in green speeds, rest assured that your Superintendent and turf staff work towards consistency and maintaining appropriate green speeds every single day.
Turf Team
RattleSnake Point Golf Club