Date: Thu 11 May 2006

Seashore paspalum

The Warm Season Grass For Today’s Environment?

By Stewart T. Bennett, Saltscape Solutions

Abaco Golf Club

Abaco Golf Club

Environmental issues are becoming more and more of a concern for new golf projects throughout the world, especially in many Southern European countries where there are many competing demands for fresh water as well as concerns over water quality and stewardship of the environment. It is a common misconception that all grasses involve similar levels of maintenance, but that is not the case. A species of warm-season grass called Seashore paspalum (Paspalum vaginatum) is starting to become much more widely used in various parts of the world, due mainly to its exceptional salt tolerance and drought resistance, its ability to grow well with poor quality water, such as grey water, and the fact that it requires roughly half the amount of nitrogen fertilizer as Bermuda. It is well suited to many parts of the Mediterranean, especially those which remain warm in the winter.

Seashore paspalum requires similar growing conditions and provides comparable playing surfaces to Bermuda grass and is increasingly being considered for use on golf courses instead of Bermuda and the more heat tolerant cool season grasses. Not everyone is convinced of its use and this article looks at what paspalum can and cannot do.

Seashore paspalum is native to the warm tropical and sub-tropical regions of the world. Possibly it was carried to the United States when coarser textured paspalum was used as “bedding” in ships during the transportation of slaves from Africa. It subsequently came to rest on the salty shores of South Carolina and Georgia where the slaves were unloaded.

It is also highly likely that other natural avenues such as ocean currents carried the grass stolons thousands of miles to other continents. It is very difficult to prove absolute origin, but in its coarse native form this unique grass species is very adaptable to many regions and varying climates of the world.

From the original native paspalum, it is believed that varieties of the species adapted to a lower, or more dwarf characteristic. This is possibly due to grazing by animals, just as some of the early Bermuda grass varieties adapted on the plains of Africa. Paspalum has been on golf courses in different parts of the world for more than 50 years, and its evolution into a sports turf grass has been speeded up by intensive maintenance and low mowing regimes. In some places such as Hawaii it was initially viewed as a weed, but gradually some courses opted to allow the paspalum to dominate because it was so well suited to the environment that it out-competed the Bermuda and other species.

There is a big difference between the native, coarse textured paspalum and today’s current cultivars used for sports turf applications. The native paspalum may be considered invasive in some instances, but I have never seen any of the fine textured “hybrids”of today escape man’s cultivation. They just cannot persist on their own without careful management.

Paspalum is a halophyte. A halophyte is a type of plant that has special adaptations that allow it to flourish in a salty environment. Halophytes are divided into two groups: those species that actually need the salty environment to grow properly, and those where the species can out-compete other species that cannot grow in salty conditions. Often, the latter group can perform equally well in either a fresh or salty environment and paspalum is one such grass, Common Bermuda grass is not a halophyte. It has some salt tolerance, but it cannot flourish and be maintained easily, or be aesthetically pleasing in a salty environment.

So paspalum is not only a halophyte that will grow in harsh conditions, or in some cases more natural conditions, but it is also desirable as a sports turf grass that can be closely mown and maintained to form the highest quality putting surfaces. With an increasing commitment from sports turf managers to protect our natural resources, such as fresh water, and to reduce fertilizer and chemical use, paspalum is becoming an important and functional alternative.

Paspalum was first known for its tolerance to saline conditions. It is certainly highly salt tolerant but different strains can withstand different levels of saltiness. Most cultivars can put up with wind-blown sea spray and occasional inundations of ocean water flooding. The Abaco Golf Club in the Bahamas, designed by EIGCA Senior Member Tom MacKenzie while he was with Donald Steel and Company, was battered by two hurricanes in a two week period during the grow-in. Some areas of the golf course had up to two meters of seawater standing on them for several days but, due to good soil texture and after flushing it with fresh water, the grass quickly recovered.

However, although it has been stated by some that paspalum can be irrigated with sea water, it is certainly better to avoid this. Paspalum will survive with high levels of salinity such as in the case of sea water, but it will be extremely difficult, if not impossible, to sustain growth and development to achieve a high quality turf grass sward, required for good golf.

The most important issue when considering paspalum and its salt tolerance will be the soils. To put it simply; a soil that is high in organic matter and/or has a fine textured particle size, is less able to grow good grass in salty conditions. On the other hand; if a soil is very low in organic matter and is coarse textured and well drained in nature, one could use a relatively high level of brackish or salty water. The chemistry and interactions of soil types and water quality is a highly complicated issue where all elements are inter-related.

Paspalum has a much better drought tolerance than most other warm season grasses when maintained properly. There are several reasons for this. Firstly, most halophytes are drought tolerant as they originated, even in tropical climates, on drier coastal sites. Secondly, paspalum has a deep and extensive root system. Like Bermuda grass, paspalum grows by stolons and rhizomes but unlike Bermuda, its rhizomes can be found more than five centimetres deep, and roots have been recorded up to about two meters deep. Irrigation rates will vary with the soil type, the water quality and the time of year, but Abaco Golf Club (after grow-in) is currently using less than 20mm of water per week on greens, tees and fairways, even in the driest periods.

When Seashore paspalum is used in either fresh water or salty water environments, the total yearly use of nitrogen will be much lower than for other warm season grasses - possibly up to 50% or more. When paspalum is utilized in saline sites, the nitrogen will still be low, and the phosphorus and potassium may be the same, or sometimes a little higher. A higher level of soil potassium is sometimes needed in saline sites to help the plant overcome the elevated levels of sodium in the soil.

Overall, the total fertilizer use for paspalum is much lower than equivalent grasses. Again this is due mainly to its origin of coastal, salty sites where it received only nutrients from sea water. Sea water is very low in nitrogen, but has fair amounts of potassium, magnesium and other nutrients. In fact, paspalum is similar in these characteristics to many of the fescues that are found close to the sea in cooler regions.

Another benefit of Paspalum is that it has relatively low disease incidence, when it is maintained properly, and tends to have better disease resistance than Bermuda grass. However, over feeding of nutrients, especially with nitrogen, will promote an over abundance of growth and encourage thatch build up and, as with any warm season grass, high levels of thatch can promote disease. Control of insect problems on Paspalum requires similar management tools as for Bermuda.

Paspalum has a wide range of tolerance to soil pH from about 3.5 to 9.0. Although it will survive in either highly acid or highly alkaline soils, in these extreme conditions nutrient availability can become a problem and top quality surfaces may be difficult to sustain.

The finest leaved cultivars of paspalum, such as SeaDwarf, can be mown to 2.5mm (1/10”) and perform to a similar level of the Ultra Dwarf Bermudas. As more courses adopt paspalum, the enlightened skills of the golf course superintendent will further improve the performance to a level where it may well start alongside the best of the bentgrasses.

On fairways, the fine cultivars perform perhaps better than other grasses, producing drought tolerant surfaces that are finer and firmer than 419 Bermuda.

If the grass has a weak point, then it may be its dislike of scalping. It can struggle to recover from this damage and look unsightly for a while where this damage occurs. Scalping can be caused by improper management such as too much nitrogen and infrequent mowing and is usually the main reason paspalum becomes prone to disease. Proper management from adequate knowledge is the best tool to prevent this problem from occurring.

As a transitional grass, paspalum performs equally as well as Bermuda. Paspalum will stay greener a little longer than Bermuda, but it may take slightly longer in the spring to green up again. Important maintenance factors such as adequate soil moisture and proper nutrient levels before the onset of cool weather will allow paspalum to sustain colour and growth well into the cool season. It is possible to keep paspalum lush-green and growing through the winter months with night-time ambient air temperatures less than 0ºC and sub-surface soil temperatures near 6ºC. Temperatures such as these on several occasions pose no problem, but constant, very low temperatures will cause paspalum to go dormant just like Bermuda grass.

It is easy to under-estimate the value of Seashore paspalum in many warm season areas. It is worth repeating that it uses roughly half of the water and fertilizer, can withstand and, indeed, thrive when using salty water and still provide playing surfaces that are as good as those provided by equivalent grasses. How often does a “new” sportsturf grass come along that is proven to deliver this? It is not for everyone, but it should always be considered where the climate and soils are suitable.

This article first appeared in the Institute's Yearbook for 2006-2007.

Golf Course Design