Flora-Fauna

Nasturtium officinale W.T.Aiton

(Hortus Kew., ed. 2, 4: 110; 1812 – Nouvelle Flore du Liban et de la Syrie, vol. 1, Pl. XLVII nº 1; 1966)

• Life-form & habit: Perennial aquatic or semi-aquatic herb with creeping, hollow stems rooting at the nodes. Stems 20–80 cm long, floating or ascending, smooth and succulent, forming dense mats in shallow water.

• Leaves: Alternate, pinnate with 3–9 leaflets; terminal leaflet larger, ovate or obovate, 10–25 mm long; lateral leaflets smaller, roundish to elliptic. Petiole winged; blades glabrous, dark green and fleshy.

• Inflorescence & flowers: Racemes lax, elongating in fruit; flowers 4–6 mm in diameter, white; petals obovate, twice the length of sepals; stamens 6, tetradynamous. Ovary sessile, elongate.

• Fruit: Silique slender, cylindrical, 15–25 mm long, erect or slightly curved, containing numerous yellowish-brown, ovoid seeds in two rows per locule.

• Phenology: Flowers and fruits almost year-round in permanently wet habitats; peak flowering from March to July.

• Habitat & elevation: Clear streams, springs, irrigation channels, and marshy meadows; thrives in cold, oxygenated running water, from sea level up to 1 900 m. Intolerant of stagnant or polluted water.

• Lebanese distribution: Frequent and locally abundant in Mount Lebanon (especially Baabda, Aley, Sannine, and Barouk) and in the Beqaa Valley (notably Zahlé, Rashaya, and Ain Dara). Mouterde (1966) recorded it as a dominant aquatic herb in clean mountain springs and flowing waters.

• Native to: Afghanistan, Albania, Algeria, Austria, Azores, Baleares, Belgium, Bulgaria, Canary Is., Cape Verde, Central European Russia, Chad, Corse, Cyprus, Czechia-Slovakia, East Aegean Is., Egypt, Ethiopia, France, Germany, Great Britain, Greece, Hungary, Iran, Iraq, Ireland, Italy, Kazakhstan, Kirgizstan, Kriti, Krym, Lebanon-Syria, Libya, Madeira, Morocco, Netherlands, North Caucasus, NW. Balkan Pen., Pakistan, Palestine, Poland, Portugal, Romania, Sardegna, Saudi Arabia, Sicilia, Sinai, Spain, Sudan-South Sudan, Sweden, Switzerland, Transcaucasus, Tunisia, Turkmenistan, Türkiye, Türkiye-in-Europe, Ukraine, Uzbekistan, West Himalaya (POWO).

• Introduced into: Widely naturalised across all continents including Africa, the Americas, Asia, and Oceania — notably in North and South America, sub-Saharan Africa, India, Australia, and New Zealand (POWO).

• ⚠️ Taxonomic note: Nasturtium officinale, the true watercress, is a cosmopolitan hydrophyte distinguished by its creeping hollow stems, glabrous pinnate leaves, and white cruciform flowers. Mouterde (1966) emphasized its abundance in Lebanon’s mountain springs and described it as one of the clearest indicators of unpolluted freshwater ecosystems. The species is edible and medicinal, often confused with N. microphyllum, but differs by its broader terminal leaflet, glabrous rachis, and less branched inflorescence.