Growth Regulators on Golf Courses

In the USA and the UK, growth regulators are used much more frequently than on our (German) golf courses. Not only do they affect grass growth, but also the quality of the sward. Their use was discussed as part of coronavirus-related closures, as reduced growth makes it possible to reduce the frequency of mowing. However, many greenkeepers lack experience or remain unconvinced because of the reduced ability of the grass to regenerate in the event of an outbreak of disease.

Mr. Heyne, for how long have you been working in the lawn sector?

For a good 24 years now: for the first 17 as a greenkeeper and for the past 8 as a special consultant for lawn care at ICL.

Our topic is the use of growth regulators. Have you used them in the past?

I was trained in floriculture, where growth regulators are commonplace. They’re often used to help produce compact plants, for example, and applied frequently in other areas of the green industry too. You can induce changes with cultivation management, so by applying fertilizers and irrigating, but it’s often not enough.

Have you used growth regulators like Primo Maxx in the lawn sector yourself?

Quite honestly, no, I haven’t. I believed that I could cultivate an equally good lawn for golfers without the need for growth regulators. I was also slightly reluctant to jump onto every trend in the industry.

And now you’re an advocate of growth regulators?

Yes, 2 years down the line, I have started working in the field for ‘the sector’ and have seen the quality of the lawns treated with products like Primo Maxx by fellow greenkeepers. My previous assessment that grass could look just as good without it was false.

What effect does the Primo Maxx growth regulator have on the plant?

The leaf blades grow at a slower rate as synthesis of gibberellins is reduced. Gibberellin is a plant hormone that is responsible for cell stretching. The plants also grow better, so they have more shoots. This increases the density of the lawn. The root mass increases, which boosts the vitality of the individual plants and makes the lawn more stable.

Is the reduced growth noticeable when mowing?

Yes. The reduced growth means a reduction in mowing across all game elements. This saves on labor and materials, such as fuel. It also helps to increase the service life of machinery and equipment. These savings apply in particular to pre-greens, tees, fairways, and maintained roughs. I think that the savings are slightly less on the greens, as they need to be dew whipped every day. This is usually done while mowing. When you use Primo Maxx, you can mow every two days, but dew whipping and rolling of the green still need to be done.

Can you quantify the reduction in mowing?

According to a Swiss study, the production of cuttings is reduced by around a half, although that does not mean that the amount of mowing is reduced by a half. A study by STERF (editor’s note: Scandinavian Turfgrass and Environment Research Foundation) suggests that using growth regulators means that you can reduce mowing on fairways by a third. You can alternate between mowing and rolling on the greens, but that’s just an economic aspect.

What do you mean?

Well, a reduction in mowing is a purely economic aspect. The other aspect is to increase the quality of the grass for golfers.

Do you play yourself?

Yes, I try to make my game look good on occasion.

What quality improvements can be realized by using growth regulators?

Let’s start with the tees: the density of the lawn increases as the formation of side shoots is increased. This in turn makes the tees more stable and resistant to shear. The reduced number of cuts means that the plants have to devote less energy to closing the wounds, which means less stress. This is particularly true for shady tees, where there is typically increased length growth although I must say that eliminating excess shade should always have top priority.

On the fairways, the increased number of shoots improves the ball position, which means that the ball isn’t topped quite so frequently. During times with particularly good growth conditions, growth regulators significantly reduce the quantity of cuttings, and that helps to improve the overall appearance of the golf course. The same also applies to maintained roughs. In the event of heavy rainfall before an important tournament, you can skip mowing once in a while. The reduced length growth gives greenkeepers a bit more flexibility and space to maneuver.

How about the greens?

Growth regulators ensure that the greens still have good rolling speed, even twelve hours after the morning cut. This is particularly important for players who work during the day and like to go out in the evening, expecting good conditions. According to STERF, the green speed between the greens is more consistent and varies less throughout the course of the day. It is also possible for greenkeepers to offer a higher rolling speed throughout the day, while maintaining an acceptable cutting height for the grass. Primo Maxx keeps the Poa annua inflorescences shorter, which gives a more constant ball run.

Mr. Heyne, thank you for talking to us about this interesting topic and every success with your efforts—not only in your game, but also in keeping your lawns in good shape.

As published in Greenkeepers Journal 2/2020