Crypsis schoenoides
(swamp pricklegrass)

C. schoenoides is an annual grass, with a native distribution ranging from southern Europe and North Africa, across Middle East, to northern India and China. It has been introduced into North America, Australia, Madagascar and Japan, where it has naturalized. However, it is only considered to be a major invader in California, where it is very abundant in wetlands and other waterbodies. Its dominance in these habitats, where it forms dense mats, means it is likely to have negative impacts on plant biodiversity in Californian wetlands.

The native distribution of C. schoenoides encompasses a large range including Mediterranean Europe, the Balkans and south-eastern Europe, North Africa, the Middle East and extending through Asia to northern India and parts of China (eMonocot, 2015; USDA-ARS, 2015). It is also recorded as native to the eastern and southern African countries of Mozambique, Malawi and Tanzania (eMonocot, 2015; USDA-ARS, 2015).

C. schoenoides is considered as not native at the limits of its current continuous range (i.e. across Africa, Europe and Asia). For example, in parts of northern Europe (such as Belgium, the Netherlands and the United Kingdom) and in West Africa (Mali and Mauritania) it is considered to be introduced. There is also uncertainty as to the native status of this species in Senegal and Madagascar, with the USDA-ARS (2015) recording it as native in these two regions, but with eMonocot (2015) recording it as an introduced species. 

C. schoenoides has been introduced into North America, Australia, Madagascar and Japan (eMonocot, 2015; USDA-ARS, 2015).

C. schoenoides is known to be eaten by waterfowl, and the seeds are possibly spread by these birds (Naylor, 1999; Green et al., 2002; Fleskes et al., 2005). As these birds are migratory there is a risk that new introductions may occur, if populations transit from a site containing C. schoenoides to one which does not. In Michigan, USA, it has been suggested that the species has been spread along salted roadsides (Reznicek et al., 2011).

This species often grows near waterbodies such as rivers, vernal pools and marshes and can tolerate saline conditions (Hammel and Reeder, 1979; Akhani, 2014; Flora of China Editorial Committee, 2015). In California this species is actively managed in wetlands to maximise seed production for waterfowl (Rahilly et al., 2012). In Australia, C. schoenoides is known as a weed of irrigated pastures (WSWA, 1998), and in China it is reported as weed on farmland (Randall, 2012). In Israel, it has been recorded as a weed in managed forests as a result of herbicide resistance (Heap, 2015). It also appears to be common along roadsides and other disturbed areas, especially in its introduced ranges (Reznicek et al., 2011).

C. schoenoides can be highly invasive in wetlands, particularly in California (Hammel and Reeder, 1979; Calflora, 2015) and is thought to negatively affect native wetland species in this region, such as Scirpus maritimus, Schoenoplectus acutus, Juncus balticus, Xanthium strumarium and Zannichellia palustris.

Genetics

C. schoenoides has a chromosome number of 2n = 32 and is distinguished by ploidy from its sister taxon, C. vaginiflora, which has a chromosome number of 2n = 48 (Hammel and Reeder, 1979; IPCN Chromosome Reports, 2015). Peterson et al. (2014) suggested incorporating Crypsis into the genus Sporobolus, because of its embedded position in a paraphyletic Sporobolus clade.

Reproductive Biology

Like most grasses, C. schoenoides is wind pollinated and has bisexual flowers. C. schoenoides is a prolific seed producer, at least in Californian wetlands, being the most productive species in terms of mass of seed produced in these wetlands (up to 1268 kg.ha^-1 seeds produced) (Naylor, 1999). C. schoenoides has small seeds up to 1.5 mm long and with an average 1000 seed weight of 0.242 g (eMonocot, 2015; Royal Botanic Gardens Kew, 2015).

Physiology and Phenology

C. schoenoides is an annual (eMonocot, 2015). It uses the C₄ photosynthetic pathway (Osborne et al., 2014) and is tolerant of saline conditions (Flora of Pakistan, 2015). In Pakistan the species flowers from July to August at higher elevations and from September to November at lower elevations (Flora of Pakistan, 2015). In California this species flowers from June to October (Calflora, 2015) and elsewhere in the USA from June to September (Hammel and Reeder, 1979).

Environmental Requirements

C. schoenoides grows in sandy, clay or sandy clay soils in wetlands, vernal pools, moist environments in mountainous areas, seasonally-flooded mud-flats, and saline/brackish pools in deserts (Hammel and Reeder, 1979; CalFlora, 2015; Flora of China Editorial Committee, 2015; Flora of Pakistan, 2015). Climate preferences and tolerances are based on overlaying distribution records of this species in a global map of Köppen-Geiger climate zones (Kriticos et al., 2011) and global temperature and precipitation layers (Hijmans et al., 2005).

Animal feed, fodder, forage

• Forage

Environmental

• Wildlife habitat

This species is very similar to C. vaginiflora. However, it is distinguished by having pink-tinged stems and spikelets (not observed in C. vaginiflora), being taller (culms up to 75 cm compared to 30 cm), having longer leaf blades (12 cm compared to 5 cm), no disarticulation of leaf blades, glabrous collars, larger panicles (up to 3 cm long compared to 1.5 cm) and longer anthers (up to 0.9 mm compared to 0.7 mm) (Hammel and Reeder, 1979; eMonocot, 2015).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Control

There appears to be no specific literature for the control of C. schoenoides. Physical control methods such as hand pulling (especially in the early stages of an invasion) and covering with black plastic have been successfully used to control other wetland grasses such as Phalaris arundinacea and Spartina species (ISSG, 2015). Chemical control might be possible using imazapyr, because it has been successfully used on other wetland invasives (Tu et al., 2001; ISSG, 2015). However, it is interesting to note that herbicide resistance (against Group C1/5 herbicides) in C. schoenoides was observed in two managed forests in Israel in 1995 (Heap, 2015).

Monitoring and Surveillance

Remote sensing has been used to successfully map seed production of C. schoenoides (Rahilly et al., 2012). This however has not been used as a tool for mapping this species for control efforts, but rather to estimate seed production for the purposes of predicting forage availability for waterfowl (Rahilly et al., 2012).

It would be useful to know more about the invasiveness of this species in other states of the USA, and to what extent it is problematic in regions such as Australia and Japan. More information is needed on the abundance of this species, both in its native and non-native ranges. It would also be useful to know where this species appears to have expanded beyond its historical native range (in much of Eurasia and Africa).  Nothing is known about how C. schoenoides spreads outside of its native range. This knowledge would help prevent its introduction elsewhere. It would also be useful to confirm whether waterfowl are indeed dispersing the seeds of this species locally. More information is needed on whether and how this species impacts native biodiversity and what, if any, economic and social impacts it is having where it has become invasive.

27/03/15 Original text by:

Vernon Visser, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, South Africa