Celery is a common vegetable, yet its growth habit often causes confusion. The part most frequently eaten grows above the soil surface. The crunchy, pale green stalks we buy are the leaf stalks, or petioles, which emerge from a central base at ground level.
Celery’s Growth Habit
Celery (Apium graveolens) is a biennial plant, though it is typically cultivated as an annual crop for commercial harvest, meaning it is usually harvested in its first year of vegetative growth. It belongs to the Apiaceae family, which also includes carrots and parsley.
The plant grows as a rosette, with the leaf stalks emerging from a compact, central crown that sits right at or slightly below the soil line. The bulk of the marketable plant is thus aerial, distinguishing it from true root vegetables like carrots or potatoes. This crown is the transition point between the shallow, fibrous root system anchoring the plant and the expansive growth above ground.
Understanding the Edible Anatomy
The long, ribbed parts of the celery plant that people commonly consume are not botanical stems but are actually the petioles, or leaf stalks. The petiole’s primary function is to support the leaf blade and transport nutrients. These petioles are crescent-shaped in cross-section and are reinforced by fibrous “strings,” which are bundles of collenchyma cells.
While the petiole is the main harvest, the celery plant also produces edible leaves often used as a flavoring in cooking. The root system is generally not harvested for standard celery (Apium graveolens var. dulce). However, a distinct cultivar, celeriac (Apium graveolens var. rapaceum), is specifically grown for its large, fleshy, underground root.
Why Celery Looks Buried: The Practice of Blanching
The appearance of celery stalks being partially buried often stems from a traditional cultivation technique called blanching. Blanching involves limiting or completely blocking sunlight exposure from the growing stalks before harvest. This exclusion of light prevents the development of chlorophyll, the pigment responsible for the plant’s green color.
The main purpose of blanching is to improve the texture and flavor of the celery. Stalks that grow fully exposed to the sun tend to be tougher and more bitter due to a higher concentration of certain compounds. By blanching for two to three weeks, growers achieve a paler, more tender, and sweeter stalk.
Growers employ several methods to achieve this light deprivation, often starting when the stalks are nearly full-sized. The traditional method involves “earthing up” or mounding soil or mulch around the stalks, sometimes in trenches, leaving only the upper leaves exposed. Other techniques include wrapping the stalks with paper or cardboard sleeves, or placing boards alongside the rows of plants to shade them. This manipulation of above-ground growth creates the illusion that the plant is growing like a root vegetable.