Wednesday, May 1, 2019

The Transition Zone

Why is some of the turf at HOA vibrant green while other areas are still yellow? I'm going to give you a crash course in cool vs warm season grasses as well as breakdown why the "transition zone" is a challenge to work in.

You can clearly see the contrast between the dormant warm season and the active cool season grasses

Let's start with the obvious: The fairways and tees stay yellow far longer into the spring than any of the other turf on the property. Simply put, that's because these areas are predominantly Zoysia Grass, which is a warm-season plant. In general, plants have two options of pathways to produce carbohydrates (food) via photosynthesis. These two pathways are known as C3 and C4. These are referred to C3 and C4 because of the number of carbon atoms in the chain produced by photosynthesis. Without getting into too much depth, for the sake of this document, you can just assume that these two processes differ in a number of ways. The broad way to look at this would be to say the two pathways produce energy in different ways.

C4 grasses (warm season) are actually a great sign of evolution. The C4 pathway is just an evolution of C3 that makes that plants water imput much more efficient. This also has had some physiological changes in the plants. C4 grasses, and the whole reason we call them warm-season grasses, thrive in much warmer environments than C3. For example, C3 (cool-season grass, greens, rough, etc.) have an optimum temperature to fix carbon dioxide the most efficiently between 60 and 75 degrees. On the flip-side, C4 is most efficient between 80 and 95 degrees. So when you look out at all the yellow zoysia in the fairways in early spring, it's just because its not hot enough yet for the grass to start its photosynthesis process.

In addition to the temperatures, there are other obvious differences between C3 and C4. C3 (cool season) likes low heat, can tolerate lower light, and needs high moisture. C3 (warm season) is the exact opposite, it likes high heat, high sunlight, and can tolerate much lower moisture. So in general, we will water our cool season turf much more regularly than our warm-season turf.

So what is the "transition zone"? Well, if you are reading this you almost certainly are living in it. Basically, our climate here in Kansas City (and many other areas on the same general latitude) has weather so extreme both ways that we can grow both c3 and c4 plants. Even though this sounds like a good thing, its actually extremely hard. Essentially what it means is that for part of the season one form of grass is struggling and for the other part of the season the other grass is struggling.

We have to strategically put the correct types of grass in certain areas to make for an optimum experience. C4 grasses do not hold up well in shade so you will likely not find much healthy Zoysia in shady areas on my course. Although C4 grasses excel in our hot summers here in KC, we can sometimes lose turf from out harsh winters. C4 grass goes dormant early and has to weather many months of cold while it survives solely on stored carbohydrates from the previous fall. C3 grass excels in the spring and fall, but struggles to stay alive in the harsh summer here. Much of the plants energy is being used to stay alive and effectively take up water, so it will often shut down other growth processes to simply not die.

In other words, growing grass in the transition zone is no picnic. Hopefully I didn't bore you with too many details. The overall takeaway is the difference in cool season and warm season grasses and a little bit about why we have both here in Kansas City. If you go very far north you will likely only see cool season grasses, and if you head south you will start to see only warm season grasses.

Hope you learned something,
Enjoy the season.

Fun fact: only about 1% of all plants use the c4 pathway, and 60% of those are grasses

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