Lemongrass

Lemongrass is the dried and ground lower stalk of Cymbopogon citratus, a perennial tufted grass of the Poaceae family, two-stroke cousin of citronella grass (C. nardus) and palmarosa (C. martinii). The spice-rack form is pale greenish-khaki, fibrous, and cut into rings or milled to a coarse powder; it is a distinct product from the fresh stalk, whose juicy base is pounded or bruised into curry pastes. The aroma is dominated by citral, a pair of isomeric aldehydes (geranial and neral) present at 65 to 85 percent of the essential oil, flanked by myrcene, geraniol and limonene -- the same citral molecule that gives lemon peel its snap, only here unburdened by the bitter terpenes of Citrus pith. Two species share the trade: C. citratus (West Indian lemongrass), taller, softer-stalked, the one used in Thai, Vietnamese and Malay kitchens; and C. flexuosus (East Indian lemongrass), leaner and higher in citral, grown mainly for essential oil distillation in Kerala and Guatemala. Culinarily the dried form anchors Thai tom yum and tom kha broths, the Vietnamese pho garnish family, Malaysian and Indonesian rendang pastes, Sri Lankan curry powders and Caribbean bush teas. Because citral is volatile and water-soluble, dried lemongrass gives broths rather than rubs -- simmered, steeped, fished out like a bay leaf.