Crypsis vaginiflora
(African pricklegrass)

C. vaginiflora is an annual grass, with a native distribution ranging from northern and eastern Africa to the Middle East and India. It is known to be introduced to the USA and Mexico, but is thought to only be invasive in California, where it is common in vernal pools and wetlands. As a mat-forming species it is thought to impact negatively on native flora, although such impacts have not been documented. C. vaginiflora has also naturalized in Baja California, Mexico.

According to eMonocot (2015), C. vaginiflora is native to northern and eastern Africa and has a distribution extending through the Middle East to India. The GRIN (USDA-ARS, 2015) distribution however, includes fewer countries, with no records in the Middle East and only five African countries listed (Egypt, Ethiopia, Sudan, Tanzania, Senegal) and India.

The only records of this species being introduced come from the USA (California, Idaho, Nevada, Oregon and Washington states) and Mexico (Baja California) (Randall, 2012; eMonocot, 2015).

C. vaginiflora is eaten by waterfowl such as the northern pintail in California (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. vaginiflora to one which does not. It is also possible, due to the small seed size of this plant, that seeds may be accidentally introduced as contaminant in imported pasture seed.

C. vaginiflora almost always grows in wetlands, vernal pools or similar waterbodies (Hammel and Reeder, 1979; Calflora, 2015; NatureServe, 2015; USDA-NRCS, 2015).

C. vaginiflora appears to be invasive in Californian wetlands (Hammel and Reeder, 1979; Fleskes et al., 2005) and is thought to impact on other wetland plants in this region.

Genetics

C. vaginiflora has a chromosome number of 2n = 48, compared to C. schoenoides, which has a chromosome number of 2n = 32 (Hammel and Reeder, 1979; IPCN Chromosome Reports, 2015). It has been suggested that the genus Crypsis be incorporated into Sporobolus, because of its embedded position in a paraphyletic Sporobolus clade (Peterson et al., 2014).

Reproductive Biology

As for most grasses, C. vaginiflora is wind pollinated and has bisexual flowers. C. vaginiflora has small, dark brown seeds between 0.5 and 1.5 mm long. Seeds have an average 1000 seed weight of 0.568 g (Hammel and Reeder, 1979; eMonocot, 2015; Royal Botanic Gardens Kew, 2015).

Physiology and Phenology

This species is an annual, although smaller individuals sometimes survive through dry winters (Hammel and Reeder, 1979).

C. vaginiflora uses the C₄ photosynthetic pathway (Osborne et al., 2014). In California, this species flowers from June to September (Calflora, 2015), although perhaps from as early as May (Hammel and Reeder, 1979).

Environmental Requirements

C. vaginiflora prefers clay or sandy clay soils, often at the edges of drying lakes or in vernal pools (Hammel and Reeder, 1979). Climate preferences and tolerances are based on overlaying distribution records of this species on a global map of 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

C. vaginiflora is very similar to C. schoenoides and was for a long time considered to be the same species (Hammel and Reeder, 1979). C. vaginiflora is distinguished from C. schoenoides by generally lacking pink-tinged stems and spikelets, being shorter (culms up to 30 cm compared to 75 cm), having repeatedly-branching culms, smaller panicles (up to 1.5 cm compared to 3 cm), shorter leaf blades (up to 5 cm compared to 12 cm), shorter anthers (up to 0.7 mm compared to 0.9 mm), and disarticulating leaf blades (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.

There appears to be no specific literature for the control of C. vaginiflora. 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).

More research is needed about the biogeography, dispersal and impacts of C. vaginiflora. It would be useful to determine whether this species is invasive in regions other than California. Little is known about how this species has spread outside of its native range, and it would be useful to confirm whether waterfowl are indeed dispersing the seeds of this species locally. Almost nothing is known about how this species impacts native biodiversity.

27/03/15 Original text by:

Vernon Visser, Centre for Invasion Biology, Stellenbosch University, South Africa