Astragalus brachycalyx aka Persian Manna

Astragalus brachycalyx Fisch. is a spiny, dwarf, deciduous shrub in the legume family (Fabaceae), native to the rocky mountain slopes of western Asia from Turkey east through northern Iraq to western Iran. It is best known by its English common names "Persian manna" and "manna," and has accumulated a number of taxonomic synonyms over time, including Astragalus adscendens Boiss. & Hausskn., Astracantha brachycalyx (Fisch.) Podlech, Astracantha adscendens (Boiss. & Hausskn.) Podlech, and Tragacantha brachycalyx (Fisch.) Kuntze. The species was formally published by Fischer in 1843 and is currently treated as accepted by the World Checklist of Vascular Plants and the Catalogue of Life.

In its natural habitat the plant grows as a low, loosely branched, spiny sub-shrub with woody stems that die back nearly to the ground each winter. Mature plants typically reach 20 to 100 cm in height and inhabit dry, exposed, gravelly mountain slopes between roughly 1,700 and 3,100 meters in elevation. These conditions translate directly into its cultivation requirements: full sun, sharp drainage, and a lean, gravelly to sandy or loamy soil with very little fine earth. The plant is drought-tolerant and dislikes prolonged moisture; pH tolerance ranges from mildly acidic through neutral to basic.

The species is economically important as one of the principal sources of gum tragacanth, a hydrocolloid harvested by incising the stem about 5 cm below ground level. The gum is used industrially as a thickening and emulsifying agent in confectionery (ice cream, candies, syrups, jellies, salad dressings, mayonnaise), in textile and calico-printing dyes, in adhesives, in papermaking, in cosmetics and soaps, and as a pharmaceutical excipient for suspending insoluble powders in pills and tablets. Chemically, the gum is approximately 20–30% water-soluble tragacanthin and 60–70% water-insoluble bassorin. A particularly distinctive cultural use comes from Isfahan, Iran, where the honeydew secretion of plant lice (Cyamophila astragalicola) feeding on this species is collected and forms the base ingredient of gaz, the traditional Persian nougat.

Beyond its commercial value, the plant has attracted phytochemical attention: studies under its synonym Astragalus adscendens report high flavonoid content, strong antioxidant activity, and the presence of cycloartane-type glycosides with effects on cytokine release. Propagation is from seed, ideally sown fresh in a cold frame; stored seed should be pre-soaked in hot water for 24 hours, after which germination occurs within roughly 4 to 9 weeks at about 13°C. Astragalus brachycalyx is a wild-harvested rangeland shrub rather than a cultivated ornamental, and there is little published information on its toxicity, formal hardiness zones, or use as a garden subject.