Spartina densiflora is a cordgrass that grows caespitosely and has been known to form small meadows (Pfauth, 1998). Stems are up to 1.5 meters in length and are glabrous like the leaves which are inrolled when fresh, with pronounced ridges and leaf margins minutely ciliate. Rhizomes are present, though they are thin and wiry (Pfauth, 1998).
Spartina densiflora shows great phenotypic plasticity. It may vary between a tall form of 1.5 m and a short form of few centimeters tall (often called the Patagonian form). The density of inflorescences, spikes, spikelets, and their shape and size may vary importantly among plants (and that is why the common name “densflower” may lead to the misidentification of introduced clones) (Dr. Alejandro Bortolus, pers.comm., 2009).
Spartina densiflora demostrates a pattern of sequential development of identical growth units derived from tillers. Populations of S. densiflora are sustained by the growth of live shoots to support an annual die-back phase (Castillo, 2007). Spring to early fall is the time for rapid growth and development. S. densiflora blooms from April through July when it experiences the die-back phase with the loss of flowering culms (NWCB, 2007).
S. densiflora does not show a clear dormancy period during the year within its native range (Bortolus 2006).
Spartina densiflora provides shelter from predators and nest building material for birds in southern South America, birds include two rare and endemic species as well as nearly 35 other bird species that use the marsh for migration (Bortolus, 2006). Mammals also benefit from the growth of S. densiflora as a place to feed and breed in urban areas where other such places may be scarce (Bortolus, 2006). In native ranges S. densiflora provides mass quanitities of detritus to estuarine systems annually (NWCB, 2007).
Spartina densiflora is capable of invading a broad spectrum of habitats from intertidal marshes to terrestrial ecosystems. Soils that can support S. densiflora vary from well drained and oxygenated, to muddy and anoixc (Bortolus, 2006). Within the tidal marsh itself, S. densiflora outcompetes native flora between the lowest and highest topographic levels (Nieva, 2001). S. densiflora inhabits estuaries as well as open coastline where it succesfully populates rocky shores of softer limestone substrate or hard volcanic rock (Bortolus, 2006).
Spartina densiflora relys on both vegetative tiller production and seed germination to drive expansion over a range of salinities. The lack of a dormant period allows S. densiflora a competitive advantage over other species. Studies show that the germination rate of seeds are limited with increased salinities (Kittleson, 1997). In addition, higher desities of propagules can be found at higher elevations within the marsh. A negative correlation between rate of flowering and rate of propagule production exists (Nieva, 2001). Population density as well as competition effect these rates of establishment and reproduction as undisturbed areas are much more vulnerable to colonization success (Kittleson, 1997). Both sexual and asexual reproduction are a part of the reproduction of S. Densiflora, but the asexual role is very small in comparison (Nieva, 2001).
Principal source: Bortolus, Alejandro., 2006. The austral cordgrass Spartina densiflora Brong.: its taxonomy, biogeography and natural history
NWCB, 2007. Washington State Noxious Weed Control Board. Online database Spartina densiflora.
Kittelson, Pamela M.; Milton J. Boyd ., 1997. Mechanisms of Expansion for an Introduced Species of Cordgrass, Spartina densiflora, in Humboldt Bay, California. Estuaries, Vol. 20, No. 4. (Dec., 1997), pp. 770-778.
Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Review: Dr Alejandro Bortolus, Grupo de Ecologia en Ambientes Costeros (GEAC) Centro Nacional Patagonico -CONICET. Argentina
Publication date: 2008-05-16
Recommended citation: Global Invasive Species Database (2017) Species profile: Spartina densiflora. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1372 on 21-09-2017.