Themeda quadrivalvis
(grader grass)

Preferred Scientific Name

• Themeda quadrivalvis (L.) Kuntze

Preferred Common Name

• grader grass

Other Scientific Names

• Andropogon ciliatus (L.f.) Thunb.
• Andropogon quadrivalvis L.
• Anthistiria barbata Desf.
• Anthistiria scandens Roxb.
• Themeda chinensis (A.Camus) S.L.Chen & T.D.Zhuang
• Themeda ciliata (L.f.) Hack.
• Themeda dacruzii Birari
• Themeda echinata A.Camus ex Keng
• Themeda yuanmounensis S.L.Chen & T.D.Zhuang

International Common Names

• English: habana grass; habana oatgrass; kangaroo grass
• French: herbe de bondé; herbe de javel; herbe kangourou; herbe Saint-Paul
• Chinese: zhong hua jian

Local Common Names

• Cuba: yerba americana
• Dominican Republic: arrocillo; yerba francesa
• Haiti: herbe Dame Michel; herbe Madame Michel
• Lesser Antilles: Christmas grass

EPPO code

• THMQU (Themeda quadrivalvis)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Themeda
•                                 Species: Themeda quadrivalvis

The family Poaceae comprises 707 genera and 11,337 species distributed worldwide (Stevens, 2012). The genus Themeda comprises 18-27 species, all of which are native to tropical and subtropical regions of the Eastern Hemisphere, primarily South East Asia (Barkworth et al., 2007). Themeda species are drought tolerant and exhibit considerable ecological and morphological diversity. Within this genus, two sections are recognized based on the characters of the raceme: section Primothemedae with homogamous spikelet pairs arranged at different levels and section Themeda with homogamous spikelet pairs arranged at the same level in the raceme base (Zhang et al., 2014).

Description from Flora of China Editorial Committee (2017):

Culms moderately robust, erect or geniculate at base, 1 m tall. Leaf sheaths glabrous or with tubercle-based bristles at mouth; leaf blades flat or folded, up to 30 x 0.3-0.9 cm, glabrous, abruptly acute to acuminate; ligule 3 mm. Compound panicle large, dense; spathes and spatheoles lanceolate-caudate, glabrous, innermost 1.3-1.7 cm. Raceme composed of a triad of 1 sessile and 2 pedicelled spikelets above the involucre of 2 homogamous pairs. Homogamous spikelets all sessile, arising at same level, barren, both glumes present, 4.5-6 mm, lanceolate, stiffly setose in upper half with 3-4 mm, tubercle-based bristles. Sessile spikelet 4-4.5 mm; callus 0.8-1 mm, subacute, brown bearded; lower glume dorsally rounded, dark brown at maturity, pubescent, often thinly or glabrous on lower back; awn 3.5-4 cm. Pedicelled spikelet 4-6 mm, barren.

T. quadrivalvis was accidentally introduced to Australia in the 1930s as a contaminant in supplies of straw packing and since then it has spread as a contaminant in pasture seed. By the 1960s it was reported in Queensland (ca 1963) and soon after in the Northern Territory (ca 1967-1968). It is now well established in the Katherine and Darwin regions and continues to spread. It is also spreading rapidly along the east coast of Queensland, and into drier inland areas. It is now a major weed, especially in central coastal and northern Queensland where infestations continue to expand (Parsons and Cuthbertson, 2001; Keir and Vogler, 2006; Agriculture Victoria, 2017; Weeds of Australia, 2017).

In the USA, T. quadrivalvis has been reported as naturalized since 1945 and occurs in California, Kansas, Louisiana and Florida (USDA-NRCS, 2017). In Kansas, this species was introduced as a contaminant in seed sold for bird feeders (Towne and Barnard, 2000).

In Mexico, T. quadrivalvis was first collected in 1884 in Sonora, but this collection was fortuitous and the species was probably not established in Sonora. It was not reported again until 2006 when it was collected in a pasture along a highway in Morelos. By 2012, large populations of T. quadrivalvis were identified across the state of Morelos where it continues to spread (Sánchez-Ken et al., 2013).

In the Caribbean, T. quadrivalvis appears in herbarium collections made in 1880 in Martinique, 1905 in Barbados, 1915 in Hispaniola and 1935 in Guadaloupe (US National Herbarium, 2017).

Soil drainage

• free

Soil reaction

• alkaline
• neutral

Soil texture

• heavy
• light
• medium

T. quadrivalvis spreads by seed. Seeds are transported over long distances by both humans and animals as they adhere to fur or clothing. They are also a contaminant in pasture seed and hay and can also be spread in soil or mud moved by road graders or carried by other vehicles and machinery (Parsons and Cuthbertson, 2001; Smith, 2002; Keir and Vogler, 2006; FAO, 2017; Weeds of Australia, 2017).

T. quadrivalvis can significantly reduce the biodiversity of native grasslands, savannas, woodlands, coastal forests and rangelands, particularly in areas that are overgrazed or disturbed. It is a fast-growing grass that replaces native plants and forms tall, dense thickets that can cover large tracts of land. These dense thickets exclude almost all other species by preventing seedling establishment. It also alters the fire regime due to its greater biomass than the native plants it replaces, and hence its higher fuel load. Fires in invaded areas cause a thinning of the native woodlands and a reduction in the number of trees in the ecosystem, resulting in a change from native savannas and woodlands to areas dominated by exotic grasses (Parsons and Cuthbertson, 2001; Smith, 2002; Keir and Vogler, 2006; FAO, 2017; Weeds of Australia, 2017).

In Australia, a study showed that T. quadrivalvis can significantly reduce the richness and abundance of reptiles in invaded areas by decreasing habitat heterogeneity and structural habitat complexity required to maintain populations of native reptiles (Abom et al., 2015).

T. quadrivalvis is also a very common weed along roadsides, where it can quickly become a safety hazard by reducing visibility for drivers (Weeds of Australia, 2017).

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Fast growing
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year

• Ecosystem change/ habitat alteration
• Increases vulnerability to invasions
• Modification of fire regime
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Reduced amenity values
• Reduced native biodiversity
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - smothering
• Rapid growth

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field
• Difficult/costly to control

In India, T. quadrivalvis is used to produce fodder for livestock and for thatching (Keir and Vogler, 2006; FAO, 2017).