begins in late February to March, and continues throughout the summer and fall. Where 

 sand is actively accumulating on top of the plants, year-round growth occurs even in 

 mid-winter. However, winter cover is more sparse. 



Flowering begins in September, and continues through December. The seed is apparently 

 sterile (Palmer, 1972), thus reproduction is entirely vegetative by lateral tillering from 

 estabhshed clumps or by mechanical disarticulation of primary culms, which is of great 

 importance in recolonization after hurricanes. It is theorized that culms dislodged by a 

 storm surge are scattered in the saltwater, and redeposited as drift by the receding waters. 

 Culms have the ability to root at the nodes even when on top of moist sand. Also, foraging 

 by jackrabbits (Lepus californicus) and possibly ground squirrels (Spermophilus spilosoma) 

 are important; the culms, chewed off at the base, are scattered by strong winds. 



(d) Ecology. Bitter panicum is most common on the backshore and windward 

 slope of the foredunes where few other species compete with it. Bitter panicum occurs 

 regularly with other species less adapted to blowing sand on the lee parts of the foredunes, 

 usually on the crest or slopes. It also occurs at widely scattered locations on the mid-island 

 grassland prairie, and at Corpus Christi Bay shore at Port Ingleside. 



Bitter panicum is highly preferred by livestock, which likely is the main reason for its 

 scarcity on northern Padre during the early part of this study. Since grazing stopped, it is 

 rapidly reappearing and is now locally abundant on newly formed foredunes, especially in a 

 5-mile area south of Bob Hall Pier; it also is common on Mustang Island. Bitter panicum is 

 regular on the long-stabUized foredunes of the Big Shell area in central Padre, and is 

 appearing regularly on the backshore of the PAIS pedestrian-only beach, as well as in the 

 foredunes south to Twin Batteries. On south Padre, it is locally common in similar areas, 

 especially on the foredunes at Boca Chica at the mouth of the Rio Grande. Similarly, 

 Woodhouse and Hanes (1967) reported a recent increase of bitter panicum on the North 

 Carolina Outer Banks after cattle were excluded. On some islands off the Mississippi and 

 Alabama coasts, bitter panicum comprised about 75 percent of the foredune vegetation 

 (Lloyd and Tracy, 1901). 



(2) Shoredune Panicum (Panicum amarulum). 



(a) Geographic Range. This species is briefly discussed because of its close 

 taxonomic relationship to P. amarum. Shoredune panicum occurs along the Atlantic and 

 gulf coasts from New Jersey to Mexico (Palmer, 1972) and southeast around the gulf to 

 Quintana Roo (Sauer, 1967). 



(b) Morphology. Shoredune panicum is considered by Palmer (1972) as 

 conspecific with bitter panicum, the two being varieties. Palmer states that P. amarum and 

 P. amarulum are morphologically indistinguishable in Texas and elsewhere along the gulf 

 coast, although they become divergent and easily distinguishable in northeastern U.S. 

 However, this study found the two taxa quite distinct, both in growth habit and 

 ecologically. 



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