Halimione is a small genus of annual and perennial herbs in the subfamily Chenopodioideae of the family Amaranthaceae, placed within the order Caryophyllales. The genus is closely allied to Atriplex (oraches) — it is recognised as a distinct genus on the basis of anatomical and phylogenetic evidence, though Plants of the World Online currently includes it within Atriplex.
Plants in the genus are characterised by silvery grey, mealy stems and leaves caused by a covering of inflated epidermal bladder cells. Stems grow prostrate, ascending, or erect. The leaves are opposite in the lower part of the plant and alternate above, with oblong blades and entire margins. Plants are monoecious. Inflorescences are spicate, bearing inconspicuous flowers: male flowers have 4–5 perianth segments and 4–5 stamens; female flowers lack a perianth entirely and are enclosed by two fused, three-lobed bracteoles. The seed is vertically orientated and has a thin, membranous seed coat — distinct from the brownish, thick, hard seed coat of Atriplex. Chromosome numbers vary by species: H. pedunculata and H. verrucifera have 2n = 18, while H. portulacoides is tetraploid at 2n = 36.
The genus contains three species, the best-known being Halimione portulacoides (sea purslane), a coastal shrub reaching 1 m in height that grows in salt marshes and coastal dunes across western and southern Europe and into western Asia. It is an obligate halophyte, typically inundated at high tide. Its leaves are edible, eaten raw or cooked, and are valued as a source of micronutrients including zinc, iron, copper, and cobalt.
Etymology
The genus name Halimione derives from the Greek hali- (of the sea) and -mione, reflecting the genus's close association with saline coastal and maritime habitats. The epithet alludes to the plants' character as obligate halophytes of salt marshes and sea shores.
Distribution
Halimione is distributed across Europe, North Africa, and Asia, with a range extending from the Atlantic coasts of western Europe and the Mediterranean through Southwest and Central Asia to Xinjiang, China. The most widespread species, H. portulacoides, is found along the sea shores of western and southern Europe and from the Mediterranean to western Asia, typically growing in salt marshes and coastal dunes.
Ecology
All species in the genus are halophytes, adapted to saline coastal environments. Halimione portulacoides is characteristic of intertidal salt marshes and coastal dunes, where it is regularly inundated by seawater at high tide. The silvery-grey colouration of the stems and leaves results from salt-excreting bladder cells, a hallmark of adaptation to hypersaline conditions shared with related genera in Chenopodioideae.
Taxonomy Notes
Halimione is placed in the subfamily Chenopodioideae of Amaranthaceae and is the sister genus of Atriplex. Plants of the World Online currently subsumes Halimione within Atriplex, but recent phylogenetic research supports its recognition as a distinct genus, based on anatomical differences (notably the thin membranous seed coat versus the thick hard seed coat of Atriplex) and molecular data. The genus was described with three species: H. portulacoides, H. pedunculata, and H. verrucifera; GBIF currently lists 2 accepted descendants.
Cultural Uses
The leaves of Halimione portulacoides (sea purslane) are edible and have been used as a salad green and potherb. They are thick and succulent with a crunchy texture and a natural saltiness. The leaves contain micronutrients including zinc, iron, copper, and cobalt, making them of interest both as a foraged food and as a nutritional supplement for humans and livestock.
