Go green with hardy seashore paspalum turf
By Jay Deputy
By Jay Deputy
Seashore paspalum is the most versatile warm-season turf used in Hawai'i.
Why? First, it has extremely high tolerance to salts and can be irrigated with ocean-level saltwater. It tolerates effluent water, regardless of contaminant levels, to the extent that it can be used to clean up contaminated soils and water. It displays a high tolerance to ocean salt spray, water logging and periodic flooding.
At the same time, it requires less water than any of the warm-season grasses. Seashore paspalum also grows well in a wide range of soil types and pH ranges. It does equally well in sandy soils with pH 8 or in heavy clay soils with pH 4 or in poorly drained, muck-type soils. Because of its high salt tolerance, it can also perform in areas where salinity builds up.
Although paspalum only moderately tolerates shade, it curiously does well in cloudy, foggy or smoggy areas, allowing seashore paspalum wide ranges of locations.
The common turf-type seashore paspalum found in Hawai'i is not named, and its introduction here not well documented. It became popular in the late 1960s.
Retired University of Hawai'i turf specialist Chuck Murdock recalled that a local golf course superintendent came back from a Mainland trip with several sod cuttings from a golf course in Georgia. He began propagating it for use on his tee boxes and most of the seashore paspalum in use today is from that original planting.
Several years ago, a new cultivar called Sea Isle 2000 was introduced; it is available at some local sod farms. Other Mainland cultivars were developed but aren't available in Hawai'i yet.
Seashore paspalum closely resembles hybrid bermuda grass, although the blades are somewhat wider. Like Bermuda grass, it requires full sun for best performance and is often used as an alternative to hybrid bermuda grass on golf courses and home lawns, particularly in areas with restrictions on water use or in very wet areas.
The leaves are very soft; when properly fertilized, they are blue-green to dark green. Seashore grows very rapidly from the extension of stolons and rhizomes, and is normally planted by hydro-mulching stolons, or from sod. A seeded variety recently became available and from initial reports is an adequate alternative to vegetatively propagated cultivars. Like hybrid bermuda, it has a high wear tolerance and recovers from wear rapidly, making seashore paspalum a good alternative to hybrid bermuda in high activity areas.
Seashore paspalum responds well to regular fertilization, but excessive growth and rapid thatch development occur with high rates of nitrogen, especially in summer. A pound of slow-release nitrogen per 1,000 square feet every other month during spring to fall should be enough to maintain healthy growth and good color. More frequent applications may be necessary on sandy soils. Occasional applications of iron on soils with high pH can green up the grass without the sudden increase in growth (and more mowing).
To look its best, seashore paspalum should be maintained regularly: Mow once a week in the summer (more often, if recently fertilized) at a cutting height of 1/2- to 3/4-inch. If mown higher than an inch, the turf will rapidly develop a thick thatch and be scalped during mowing. A reel-type mower is required, since rotary mowers will not cut that low.
Do not collect the clippings; they return nutrients to the soil. Irrigate when necessary, several deep waterings per week in the summer should be enough.
Since seashore grows so fast, a thatch layer will soon develop no matter what. Removal of the thatch should be a part of the yearly maintenance schedule.
This process, called verticutting, requires special equipment, a certain know-how, and a lot of work. A professional landscape contractor is a good idea, especially if you are not familiar with the process. The best time for verticutting in Hawai'i is from April through September.
Once seashore paspalum gets established, it forms a lush carpet that keeps out most weeds. However, if weeds do get a foothold they are harder to control than on other types of turf. This is due to another curiosity of paspalum. It is highly susceptible to damage caused by most herbicides that can be safely used on other species. Apply pre-emergence herbicides every three to four months to keep weeds out. If weeds become a problem, the easiest and safest control is sprinkling rock salt on the weedy area, followed by a brief watering to dissolve the salt. This will kill the weeds with minimal damage to the grass.
I asked UH weed scientist Joe DeFrank about herbicides safe to kill paspalum weeds. The most notable of those to avoid include anything with MSMA (Weed Hoe & others) and Image, commonly used to control nutsedge and kylinga. Both of these will injure the paspalum.
Safe to use are Speed Zone Southern, to control broadleaf weeds, and Manage, to control nutsedge and suppress kylinga.
Jay Deputy is an education specialist in landscape horticulture and turf at the University of Hawaii-Manoa, Department of Tropical Plant and Soil Sciences, and Hawai'i state administrator for the Certified Landscape Technician Program sponsored by the Landscape Industry Council of Hawai'i. Got a lawncare or turf question? Contact him at firstname.lastname@example.org.