Etiolated Grass Growth

I took this photo on Tuesday afternoon on the 3rd fairway.  You can see the dense Creeping Bentgrass growth mixed with taller, leggy, and lighter yellow- green grass.  It too is Creeping Bentgrass.  There are a few different factors that can cause this.

First, this is known as etiolated grass growth.  It is a phenomenon characterized by elongated, pale green or yellowish stems and leaves. 

One of the primary causes of etiolated growth is insufficient light intensity. Grass, like all plants, relies on sunlight to produce energy through photosynthesis. When grass is deprived of adequate light, it cannot efficiently synthesize chlorophyll, the pigment responsible for capturing light energy. As a result, the grass elongates to reach a light source, leading to tall, spindly growth. This phenomenon is particularly noticeable in shaded areas, such as under trees, tall structures, or in densely planted regions where competition for light is intense.  It could also occur during prolonged days of dense cloud cover.

Another factor that can influence this is type of growth are temperature fluctuations.  While it's not fully understood, extremes between night and day temperatures can encourage this etiolated growth.

Plant growth regulators are another factor that can exacerbate this phenomenon.  While you probably didn't know such a product existed, we treat our greens, tees and fairways with plant growth regulators (PGRs) on a 14-day interval.  PGRs not only slow grass growth down to make managing clippings easier, but they are used to create denser playing surfaces.  In addition to that, they can be used to promote one turf species over another depending on their growth habit.  For example, PGRs encourage lateral grass growth, which can be used to encourage Creeping Bentgrass growth over Poa annua growth.  When turf is treated regularly for extended periods with PGRs, then those applications abruptly stop, this type of growth can occur.  Some refer to this as the rebound effect.  We stop all PGR applications by October 1st because with the drop in temperature, mother nature controls growth for us.  This rebound effect, is likely what is occurring on this fairway at Highlands CC.   

The final cause for growth like this is a bacterial infection in the turf.  I've not seen that in my career, but I understand it can be very serious in some situations, primarily on putting greens.