This species with a mainly southern European distribution is present in all regions of Italy except in the Valle d'Aosta. It grows in ruderal pioneer vegetation in rather moist sites, along ditches, streams and ponds, on sandy to silty soils rich in nitrogen compounds, from sea level to the lower montane belt. The species sporadically appears also in the outer belt of the temporary ponds of Sardinia, in contact with humid grasslands. The genus name in Latin means 'pole', 'spear', 'arrow', referring to the shape of the leaves of some species; the species name reefers to the flowers gathered in dense clusters. Flowering period: June to August.

Italian name(s): Arsom (Emilia-Romagna, Reggio), Lapazz (Emilia-Romagna, Reggio), Lavazzutt (Friuli), Lengua de vaca (Veneto, Treviso), Lingua di vacca conglomerata (Italia), Remexa (Liguria, Genova), Remixa (Liguria, Genova), Romes (Emilia-Romagna, Reggio), Romice conglomerato (Italia), Roms (Emilia-Romagna, Reggio), Romsa (Emilia-Romagna, Reggio), Rumsa (Emilia-Romagna, Reggio), Scerle (Basilicata, Potenza), Schiatta pignatte (Puglia, Barletta).