Asparagus (Asparagus officinalis var. altilis L.) is a hardy perennial vegetable. The underground portion of the plant consists of a network of rhizomes, fleshy storage roots, and fibrous roots. The fleshy roots (as well as the spears) are initiated from the rhizomes. Together, the fleshy roots and rhizome make up the crown, which is the perennial portion of the asparagus plant. Fleshy roots serve not only as storage organs for the carbohydrates received from the fern, but also as the site of fibrous root development. Fibrous roots, which live for one or two seasons, function in the absorption of water and nutrients from the soil. Asparagus spears are, in fact, edible shoots that develop on rhizomes when the soil temperature is warm and the water supply is favorable. The spears, if not harvested, develop into ferns 4-6 feet tall. Carbohydrates and other compounds necessary for plant growth and development are produced in the ferns throughout the growing season.
A half cup serving of Asparagus spears contains only about 18 calories, yet it contains 1/3 of the daily recommended dose of Vitamin C and about 2/3 of Vitamin A for an adult. It is also a significant source of dietary iron and other essential trace nutrients, when prepared without adding seasonings