growth or survival is poor or if plants do not appear healthy. In general, 

 only areas of poor plant growth will require fertilization. During the third 

 growing season, fertilizer can be applied as required to encourage growth. 

 However, sea oats are not responsive to fertilizer after the second season. 

 The response of beach grasses to slow-release fertilizers has been varied and 

 results are inconclusive (Augustine, et al., 1964; Hawk and Sharp, 1967; 

 Woodhouse and Hanes, 1967). 



d. Disease and Stress . Beach grasses vary in their tolerance to 

 drought, heat, cold, disease, and parasites. Plantings of a species outside 

 its natural geographic zone are vulnerable during periods of environmental 

 stress. American beachgrass is more susceptible to scale infestation when 

 exposure to sandblasting is reduced. Deteriorating stands of American 

 beachgrass, due to scale infestation {Eri-oaocaus aavolinea) , have been 

 identified from New Jersey to North Carolina (Campbell and Fuzy, 1972). South 

 of its natural geographic zone (Nags Head, North Carolina), American 

 beachgrass is susceptible to heat (Seneca and Cooper, 1971), and a fungal 

 infection (Marasius blight) is prevalent (Lucas, et al., 1971). 



South of Virginia, mixed species plantings are desirable and necessary. 

 The slow natural invasion (6 to 10 years) of sea oats to American beachgrass 

 dunes (Woodhouse, Seneca, and Cooper, 1968) may be hastened by mixed species 

 plantings. Thus, with better vegetation cover, the chance of overtopping 

 during storms is reduced. 



Sea oats and panic grass occur together throughout much of their natural 

 geographic zone. Mixed plantings of sea oats and beach grass are recommended 

 since they produce a thick, cover and more dune profile. 



e. Planting Width. Plant spacing and sand movement must be considered 

 in determining planting width. When little sand is moved for trapping, and 

 plant spacing is dense, nearly all sand is caught along the seaward side of 

 the planting and a narrow-based dune is formed. If the plant spacing along 

 the seaward side is less dense under similar conditions of sand movement, a 

 wider based dune will be formed. However, the rate of plant growth limits the 

 time in which the less dense plant spacing along the seaward side will be 

 effective. The spacing and pattern should be determined by the charac- 

 teristics of the site and the objective of the planting. Functional planting 

 guidelines for the various geographic regions in the United States are given 

 by Woodhouse (1978). 



The following example illustrates the interrelationship of the planting 

 width, plant spacing, sand volume, and rate of plant growth. American beach- 

 grass planted on the Outer Banks of North Carolina, at 45 centimeters (18 

 inches) apart with outer spacing of 60 to 90 centimeters (24 to 36 inches), 

 accumulated sand over a larger part of the width of the planting for the first 

 two seasons. By the end of the second season, the plant cover was so exten- 

 sive along the seaward face of the dune that most sand was being trapped 

 within the first 8 meters (25 feet) of the dune. 



American beachgrass typically spreads outward by rhizomatous (underground 

 stem) growth, and when planted in a band parallel to the shoreline it will 

 grow seaward while trapping sand. Thus a dune can build toward the beach from 

 the original planting. Seaward movement of the dune crest in North Carolina 



6-48 



