Flora-Fauna

Odontarrhena muralis (Waldst. & Kit.) Endl.

(Cat. Hort. Vindob. 2: 245; 1842 – basionym: Alyssum murale Waldst. & Kit., Pl. Rar. Hung. 1: 37, t. 31; 1802 – Nouvelle Flore du Liban et de la Syrie, vol. 1, Pl. XL nº 3; 1966)

• Life-form & habit: Perennial subshrub or suffrutescent herb, 20–60 cm tall, forming dense, branched tufts with a woody base. Stems erect to ascending, much-branched, greyish-green, and densely covered with stellate hairs giving the plant a silvery sheen.

• Leaves: Alternate, sessile, oblong to lanceolate, 10–30 × 3–8 mm, entire, acute or obtuse at the apex, covered on both sides with fine, appressed stellate hairs; upper leaves smaller and more crowded.

• Inflorescence & flowers: Terminal racemes dense at anthesis, elongating in fruit. Flowers small, 3–4 mm in diameter, bright yellow; petals obovate, twice as long as sepals; sepals grey-pubescent outside, greenish within. Stamens 6, tetradynamous; filaments slender, anthers yellow.

• Fruit: Silicles suborbicular to elliptic, 5–7 × 3–4 mm, flattened, silvery-grey when mature, densely stellate-tomentose; valves convex with a distinct median nerve; style short, persistent. Seeds 1–2 per locule, reddish-brown, smooth.

• Phenology: Flowers and fruits from April to June.

• Habitat & elevation: Rocky limestone slopes, road banks, and dry montane grasslands, 800–1 900 m. Prefers shallow calcareous soils and sunny exposures, often colonising serpentine and metal-rich substrates.

• Lebanese distribution: Recorded by Mouterde (1966) from Mount Lebanon — notably Barouk, Dahr el-Baïdar, Sannine, and Ain Dara — as well as the Anti-Lebanon, particularly Rashaya and Yanta. Locally common on open rocky slopes and screes.

• Native to: Bulgaria, Greece, Iran, Iraq, Krym, Lebanon-Syria, North Caucasus, NW. Balkan Pen., Palestine, Romania, Transcaucasus, Türkiye, Ukraine (POWO).

• Introduced into: Alberta, Austria, Belgium, British Columbia, Colorado, Czechia-Slovakia, Germany, Ontario, Oregon, Québec, Utah (POWO).

• ⚠️ Taxonomic note: Formerly known as Alyssum murale, this metallophyte was transferred to Odontarrhena following molecular and morphological revisions of the Alyssum complex. O. muralis is distinguished by its dense stellate indumentum, flat elliptic silicles, and yellow corollas. Mouterde described Lebanese populations as silvery cushions thriving on limestone outcrops, frequently co-occurring with Alyssum montanum and Erysimum scabrum. It is notable for its ability to hyperaccumulate nickel and zinc, making it of ecological and phytoremediation interest.