Who's The Boss Of The Moss?

One of the hot topics (as well as hollow coring) this summer has been moss. In particular moss on greens. I've visited lots of courses this season, speaking with many turf managers and a very high percentage have had a huge battle with moss this season with silver thread moss being the chief culprit. However, my own course, a wet, clay based parkland course surrounded by trees, has been totally free of any type of moss for the last five seasons. Why? By rights, my course should be perfect for moss to invade. I do the same as most other greenkeepers. I aerate and sand dress as much as other guys, but the two things that some greenkeepers may not be as aggressive with are my very tight height of cut (2mm) and weekly spoon feeds. Could this be it?

My key for a top greens' surface, or any playing surface to think of it is density. Creating tight, firm swards is crucial to producing top quality playing surfaces. To achieve this, on top of good cultural practises, I believe in a low cutting height and frequent spoon feeds at very low rates, just keeping the plant ticking along nicely. The tightest swards that I have seen with the greatest shoot density have been the modern creeping bents and the good old fashioned perennial poa (which incidentally is seen as a weed by certain traditionalists). Cut low, the swards get so tight on these surfaces that sometimes you have to verti-cut just to get a granular feed in to the canopy. Moss doesn't stand a chance of breaking into these swards.

We all now accept that the excessive fertility inputs of the past have no place in a modern maintenance programme as they produce soft, spongy, disease ridden surfaces that are terrible to putt on. But have today's turf managers gone too far the other way? In certain circumstances, I believe so. The heavy ammonia granular feeds of yesteryear may have produced carpet like swards and because they were so dense they did keep out the moss. However, to help gain speed on longer heights of cuts, fertility has been heavily reduced in certain turf programmes. This has produced weaker swards ideal for pests like moss to gain an advantage. This is where I think frequent spoon feeding has a place in a modern turf programme.

With frequent, light rates, spoon feeding can give you a sward that is growing at a controlled rate. The advantages of this are increased speed and smoother ball roll as growth is controlled but, more importantly for moss control, a stronger sward that helps to suffocate this pest out.

I don't assume that I have the total answer to the question of moss, but having thought about it over the past few months I ask you to consider that there may be a link between cutting heights and fertility. What goes without question though is that the greater the sward density, the more chance you have of keeping moss at bay. If you have reduced your fertility over the last few years and seen a dramatic increase in moss, try upping the fertility levels again. It may be as simple as that!


We had a couple significant areas of moss when I first got to Northland. From the beginning I wanted to attack it from a cultural standpoint, rather than continue to hit it with a chemical each time we sprayed. IMO, when moss or any other undesirable agent (including Poa) is present we must first identify the reason it persists, then work off of these issues in order to solve the problem.

In our case the moss was present due to a few factors.

1. Lowering of mowing heights and traffic.
2. Surface disruption.
3. Low rates of N.
4. Consistently wet surfaces.

The first thing we did was to dry out the surfaces by using deep/infrequent irrigation. This worked to a point but during wet periods the moss once again flourished. While we made headway the moss was still present.

The next move we made was to begin regular application of ferrous sulfate. This was done as part of a bentgrass promotion program but also had a negative effect on the moss.

At the same time as beginning the ferrous sulfate apps we also quit vertical mowing and core aerating and we switched our mowers to smooth rollers.

At times we have increase N to the moss areas but generally N rates have not been changed. The moisture gave us a great start but when we added the ferrous, the non-disruption of the surface and the smooth rollers, the moss soon disappeared.

To me moss and Poa are very similar. Both come into surface very easily when conditions are right but getting them out is much more difficult.

As superintendents I believe we need to think more about what sort of cultural conditions we are producing and whether or not those conditions are benefiting the "pests" we are looking to eliminate. Before relying on a product we should change the culture and see what happens. It does not happen quickly but it will happen.

Great to see you promoting a change in culture rather than a product.

Great post and topic.  I just posted some pics on G+ in a discussion with a couple of guys talking about moss.  I started back today after a layoff to see the moss I thought was dead or about dead as of last fall only to see it flourishing.  We are changing some cultural practices on greens and we try to dry them out as much as possible with deep watering like Chris does.  We did switch to more granular fert as roots were shallow and we saw good results growing them but the moss continued to flourish.  We plan on doing more topdressing and rolling and less mowing and I'll have to plug the worst spots but and hopefully with a couple of chemical apps and the changes in cultural we can reduce the population and squeeze it out with good grass.