In college I was taught how the cool season grasses we have in Canada grow. This growth habit was drilled into our heads and is found all over the internet. The classic spring growth surge, followed by a decrease in growth in the hot summer months with another big surge in the fall.
While this is how unirrigated turf grows in Canada, it isn’t how grass on a golf course grows under normal conditions. This wasn’t a huge surprise to me because I had been measuring growth rates since 2011. Even though I knew in the back of my head that grass didn’t grow this way I was still managing my course as if it grew based on the classic cool season growth model.
It wasn’t until 2012 when I came across the growth potential model from Pace Turf that it became clear to me how I should better manage my turf. Originally developed to better time overseeding in the South, the growth potential model can help turfgrass managers make better decisions about all maintenance practices and how we time them.
While it might seem a little complicated at first, it basically just takes our temperatures and spits out a percentage of optimal growth for your climate and time of year where 1 is optimal and 0 is no growth. When put into a spreadsheet all you need to do is add the temperatures and it does the complicated math for you.
For the most part, growth rates are dictated by the air temperature. Turf managers can massage the growth rates either higher or lower with tools like fertilizer, growth regulators and water but for the most part, temperature is the boss. Think of it like this, if it’s freezing out, nothing you do will make the grass grow except increased temperatures. The same is true for when it gets too hot. When it’s too hot the plant cannot make enough energy and bad things can happen if the turf is pushed too hard. This is often why we see issues with dead grass in the summer months. It simply gets too hot for our grass.
All of a sudden, we have the tools to manage the turf in our specific climate and not on one big general idea of how grass grows in one specific part of the world. Every golf course is different so we should manage them differently to get optimal conditions.
One of the first ways I used growth potential was to schedule fertilizer applications. I used to make big applications in the spring and fall and would back off in the summer months. This resulted in Ok conditions but left us to deal with excessive clippings in the spring and fall and disease and traffic prone grass at all time of the year. Growing grass without taking the growth potential into account was a costly endeavor. We were mowing like crazy where we now hardly have to dust off our mowers in the Spring or Fall.
For me, one of the most interesting things about matching my fertilizer rates was the impact it had on turfgrass disease. One of my missions since our threat of a pesticide ban in 2010 was to try and find ways of managing my turf with less pesticides because if they were banned I wanted to still have grass to maintain!
When I was applying high amounts of fertilizer in the spring and fall it would make diseases like Microdochium nivale much worse. Generally, this disease is worse on lush, actively growing grass and much less pervasive on lean, slower growing grass. Of course, there are exceptions.
The same things were true for diseases like Dollar Spot. Applying low amounts of nitrogen in the summer months can make this disease much worse and this was exactly what I was doing before adopting the growth potential model for fertilizer scheduling.
The winter of 2016/2017 saw a lot of winterkill on the West Coast and I again went to the growth potential formula to help me make better decisions for recovery of our damaged greens. I compared our actual growth potential to the average growth potential in my climate and found that the weather was much cooler and less ideal for growing in new greens. This helped me focus on trying to heat up the greens instead of only relying on fertilizer to grow the grass faster. This also helped me explain to the golfers why we were having such a challenging time recovering from the damage. I never thought growth potential would be such a valuable communication tool for my membership.
you are having and allow you to make the right decisions when it comes to winter damage recovery.
This summer we were again faced with some challenging weather, namely, heat waves that are not common on the West Coast. I again went to my growth potential model to help me manage my turfgrass with more certainty and consistency. As the temperature goes above 20C the growth potential goes down and this is when we as turf managers need to be careful of pushing our turf to the point of catastrophic failure. By knowing when this happens I could confidently raise heights, back off on mowing and rolling, and put more resources into ensuring the grass was adequately watered. The result is that we lost very little grass this summer and the greens are in fantastic shape going into the fall golf season. Again, it was also helpful for me to use this data to communicate to the golfers why the greens might be a little slower than normal while we transition through the periods of extreme heat and turfgrass stress.
If you haven’t already I highly recommend checking out the growth potential model to see if it can help you explain some of the issues you have managing the turf in your specific climate. I talk a lot about the growth potential and how I use it on my blog Turfhacker.com
Jason Haines is the golf course superintendent at Pender Harbour Golf Club in British Columbia, Canada. He is a passionate turfgrass manager with a love for the outdoors and enjoys trying new things and pushing his personal boundaries. Haines achieved a diploma in turfgrass management technology from NAIT (Fairview College). He also received an award from Golf Course Industry magazine in 2014 for Best Blog/Savvy Social Media and was a Merit International Winner for the 2017 Environmental Leaders in Golf Awards. He is an active user of social media (@pendersuper) and has been sharing his ideas about greenkeeping on his blog www.turfhacker.com since 2011.
