PlantaeDB Logo
Login Sign-up

Genus Gastridium in Family Poaceae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Gastridium (family Poaceae, subfamily Pooideae) is a small, annual genus comprising about two species, centered in the Mediterranean but extending to Macaronesia and naturalized in several temperate regions. The type species is Gastridium ventricosum (Gouan) Schinz & Thell., widely known as nitgrass. The genus is readily recognized by the swollen, globular base of the lemmas (ventricosus), awnless or shortly awned lemmas, the presence of a long, sharply defined palea-keel and prominent, stiff lemma keels, and tough, indurated lower glumes that often persist on the culm after spikelet fall. Plants are tufted annuals with flat leaf blades and open panicles that become dense and spike-like in fruit.

Species diversity and geographic patterns mirror the Mediterranean climate gradient. Gastridium ventricosum is a widespread Mediterranean taxon, abundant in open, often disturbed, dry to mesic grasslands and roadsides from sea level to montane elevations; it occurs in southwestern Europe, North Africa, the Canary Islands, and Macaronesia, and is introduced in parts of North America, Australia, and South Africa. A second, less frequently recognized entity—either treated as G. phleoides (Nees) Chiov. or as a southern African form within G. ventricosum—occupies comparable habitats in South Africa and Lesotho. Within the Mediterranean core, the genus favors dry, summer-parched grasslands and coastal scrub, extending into montane screes; patterns are broadly coherent with other Mediterranean annual grasses.

Pollination biology in Gastridium conforms to wind pollination typical of grasses, and seed dispersal is primarily ballistic from shattering panicles, sometimes aided by adhesion via the hardened glumes. Little anatomical specialization beyond the indurated lemmas and glumes is documented. The base chromosome number remains unstable across reports, and no single count is consistently supported; present cytological notes are therefore not emphasized.

Taxonomically, Gastridium is monophyletic within the core Poeae clade (Saarela et al., 2018) and often resolved near Ventenata and the Aegilops-Hordeum complex in phylogenies of annual Pooideae. The genus lacks formal sectional or subgeneric treatment, and while most sources accept G. ventricosum as the sole Mediterranean species, the South African taxon is variably treated: either as G. phleoides or as a conspecific form within G. ventricosum. Alternatives are reflected in major checklists and regional treatments (POWO, 2024; WFO, 2024; Tzvelev, 2007; Chiapella, 2007).

Human relevance is largely ecological. Gastridium ventricosum is a minor pasture grass and an occasional weed of cereals and field margins; it may increase under disturbance but is not widely recognized as invasive. Its ornamental value is modest.

Conservation concerns are localized: some southern African populations appear vulnerable to habitat degradation and drought intensification; conversely, Mediterranean populations are typically common. Research gaps persist in species limits across South Africa and Macaronesia and in clarifying cytological baselines for the genus (Saarela et al., 2018; Tzvelev, 2007; Chiapella, 2007).

Pick a Species to see its components: