The Evolution Of A Putting Green
By David A. Oatis
Ever wonder what happens as a putting green ages? Many golfers just assume that once a green is built, the work is done. Nothing could be further from the truth. Building a new green really just starts the process of evolution and natural selection. Read on to learn more about what happens as a putting green ages.
Putting greens, once built, take on a life of their own and can eventually evolve into something very different from what was originally designed or envisioned. So why is this significant? Building a putting green, really just starts the process of evolution. In many respects, the golf course superintendent’s primary job is to try to manage or steward the evolutionary process, hopefully ensuring that the changes are desirable in the long run. This article will concentrate only on the more common changes that occur to putting greens as a result of play, management practices, the passage of time and the effects of natural selection. Be assured that the changes occurring to bunkers, tees, fairways, and tree plantings, etc. may be even more drastic.
An improperly built or managed putting green will often require extensive and involved management practices to help it perform adequately.
Thatch Development and Management
Thatch development is a normal and necessary process; the key is to manage it. Seeded greens initially have no thatch, and although excessive thatch is a common problem, some thatch must be developed before a green can be opened for play.
Once greens begin to grow, regular topdressing should commence immediately to intersperse sand particles in the thatch as it develops. The thatch/mat layer must be adequately diluted to ensure effective drainage, gas exchange and root growth. As the green matures, the surface becomes increasingly firm and resilient and allows the turf to handle traffic without excessive injury. On the other hand, excessive accumulation of thatch or insufficient dilution of thatch with topdressing, are very common problems of new greens. Other problems also occur:
- Shortened root growth
- A soft surface that is prone to foot-printing, scalping and rutting.
- An excessive thatch layer functions much like a kitchen sponge. It may allow for the transmission of water, but it will retain too much at the surface. A wet surface creates a perfect environment for algae, moss and annual bluegrass invasion.
- Thatchy, wet surfaces result in deep, pitting ball marks.
- If the surface stays wet, gas exchange declines and roots die back.
- Wet surfaces increase disease pressure.
Clearly, developing a sound cultivation and topdressing program is of critical importance to the long term health and playability of the putting green. There are many ways to manage thatch, and much research and articles have been published on this subject. Cultivation and topdressing programs vary widely, but the point is that an effective thatch management program is essential.
Greens established from sod present a different set of problems. They often can be opened sooner than seeded greens, but extra cultivation usually is necessary to alleviate the layering that typically results from establishment with sod. Golfers obviously dislike the extra cultivation, but it is the long-term downside to establishing greens from sod.
Rigorous testing should be performed on the components a green is to be built from before construction begins. It is not enough that the root zone mix meets the USGA Putting Green Construction Guidelines. It also must be appropriate for your specific geographic area and project.
- The infiltration test is one of many that provide guidance in root zone mix selection.
- Regardless of what the initial infiltration number is, this number may drop by as much as 70-80% in the top few inches of the green where the majority of the thatch develops.
- If thatch is not managed properly, the infiltration rate at the surface of the green may drop dangerously low, thereby contributing to all of the problems previously described under thatch management.
This illustrates the importance of proper management of the thatch layer. Assuming that the initial root zone mix selected was appropriate and it is properly managed, its drainage properties should remain adequate indefinitely.
Greens usually take several years to mature to a point that they can withstand the same type of wear and tear a mature green can. The maturation process depends on:
- Weather and growing environments
- Length of growing season
- Species and cultivar
- Construction methods and materials
- Pre and post establishment inputs (i.e. irrigation, fertility)
Greens in poor environments usually take longer due to their reduced vigor. New greens usually need to be managed conservatively in their first few years, so it is wise to reduce stressful maintenance practices during tough weather or the green begins to show signs of stress.
Some golfers seem to like the uniform color and blemish-free appearance of a brand new putting green, and these golfers may complain when the grasses begin to segregate. Segregation refers to the “sorting out” of individual clones or biotypes the grass cultivar was planted with.
- Different clones/biotypes segregate out into patches, gradually becoming visible to golfers.
- Segregation can be especially noticeable on putting greens in the early spring and fall when temperatures are cool.
- During cool temperatures, different biotypes change color and grow at somewhat different rates, thereby enhancing the “patchwork” appearance.
Generally speaking, segregation becomes more noticeable the older the green.
In the Northeast, annual bluegrass (aka Poa annua) is the most common weed to invade putting greens. Newer courses often struggle valiantly to keep annual bluegrass out of their putting greens, and currently a variety of materials and strategies can aid in control. Nonetheless, annual bluegrass almost always invades and usually becomes a significant component of the putting green turf population. Annual bluegrass is a major component in the greens at most older courses, and some wonder whether they should try to keep it out in the first place. When annual bluegrass greens are good, they are great; but, when they are bad, they are producing seedheads or they are dead!
- Annual bluegrass is very susceptible to many turfgrass diseases, insects and winter injury.
- Annual bluegrass can be kept alive during many years, but there are weather patterns that virtually guarantee widespread loss in other years.
- Annual bluegrass often is more wear tolerant and is uses of light very efficiently. Thus, in low light and high wear situations, annual bluegrass may actually be the better adapted species when compared to creeping bentgrass.
There are thousands of different biotypes of annual bluegrass. Some are very desirable because they have fine texture and are tolerant of low mowing. There also are many undesirable biotypes. These produce the most seedheads, are the least tolerant of stress and disease, and may be true annuals. These are the types that fail most often and are the types that typically invade putting greens first.
Annual bluegrass encroachment into a new putting green has significant consequences. Initially, it may go unnoticed because individual plants become established at first.
- Annual bluegrass patches are most noticeable in the spring and fall, due to their prolific seedhead production (spring) and when the creeping bentgrass is off color (early spring and fall).
- During the summer months, annual bluegrass usually blends in better with the creeping bentgrass.
Natural selection works for courses that can keep annual bluegrass alive. Over time, the weaker, less desirable biotypes are gradually replaced with finer textured, more stress tolerant biotypes that are more hardy and attractive. For some, annual bluegrass is a noxious weed, but for others it is the species of choice.
The environment a putting green occupies has a greater impact on its performance than any other factor, bar none. Simply put: a perfectly built green with the best grasses will perform poorly in a poor environment. Conversely, a marginally built green may perform adequately in a very good environment. So what constitutes a good or bad environment? Simple: sunlight and air circulation. There are products and practices that can help improve the performance of turf that is grown in a poor environment, but none can overcome the effects completely. Shaded, pocketed environments result in:
- Weaker, thinner turf stands with reduced vigor, energy reserves, and recuperative potential
- Disease pressure is greater as a result of the higher relative humidity.
- Soils remaining wet for longer periods
- Higher annual bluegrass populations
The grass growing environment turf is located in is enormously important!
Putting Green Shape
Greens often get smaller over time, and irregularly-shaped greens frequently become more rounded. Unless extreme care is taken, courses over 10-20 years in age usually experience significant changes in their shape and lose cupping area. Loss of cupping area can affect playability and turfgrass health.
- Smaller putting surfaces cause traffic to be concentrated on less area.
- Shrunken greens may play very differently than originally intended.
- Perhaps most important, golfers are cheated out of playing to hole locations envisioned in the original design.
Most older courses can be improved significantly by expanding greens back to their original shape.
The surface contours of a putting green can change slightly over time. Minor settling may occur after establishment, but these changes are usually irrelevant. Sand, blasted out of a heavily used bunker, can build up the grade of a greenside bank. A number of problems can occur if the buildup becomes extreme:
- The buildup occurs primarily on the bunker banks, but when the bunker is close to the putting surface, the buildup can extend into the green, altering the surface contours on the putting green.
- The change can eliminate usable hole locations and may block surface drainage, increasing the potential for turf problems.
Some change in the contours of greens likely happens over time as a result of cultivation and topdressing practices, but the changes are so subtle that the human eye could not possibly notice it. Given the number of 100-year-old courses that still have severely contoured putting greens, the change must be very minor indeed.
This article may spur many questions regarding the different subjects covered. Read the article in its entirety at /content/dam/usga/pdf/imported/putting_green_evolution(1).pdf along with numerous related articles.
Dave Oatis is director of the Green Section’s Northeast Region.