By Harold McGee
Asparagus is the main stalk of a plant in the lily family, Asparagus officinalis, a native of Eurasia that was a delicacy in Greek and Roman times. The stalk doesn’t support ordinary leaves; the small projections from the stem are leaf-like bracts that shield immature clusters of feathery photosynthetic branches. The stalks grow up from long-lived underground rhizomes, and have been widely prized as a tender manifestation of spring. Many other vegetables have been called “poor man’s asparagus,” including young leeks, blackberry shoots, and hop shoots. It remains expensive today because the shoots grow at different rates and must be harvested by hand. In Europe, the even more labor-intensive white version, blanched by being covered with soil and cut from underground, has been popular since the 18th century. It has a more delicate aroma than green asparagus (which is rich in dimethyl sulfide and other sulfur volatiles), and some bitterness toward the stem end. Exposed to light after harvest, white asparagus will turn yellow or red. Purple asparagus varieties are colored with anthocyanins, whose color generally fades during cooking, leaving the green of the chlorophyll.