What is the botany of celery?

Celery is Apium graveolens var. dulce (graveolens meaning strong-scented and dulce meaning sweet). It is in the Umbelliferae family, whose members have compound umbrella-shaped flowers. Other members of the family include carrots, fennel, parsnips, chervil and parsley. Celery and Celeriac (Apium graveolens var. rapaceum) are the only members of the genus Apium which are important horticulturally. The characteristic flavor and odor of plants in this fail are due to folatile oils in the stems, leaves, and seeds.

Life-cycle. Normally celery is a biennial taking two seasons to produce seeds and complete its life-cycle. During the first season, it grows vegetatively. During the second season, the short main stem elongates to 2 to 3 feet and branches to produce a shrubby plant about 3 feet tall. The plant bears white, inconspicuous flowers in compound umbels. These produce flattened, small fruits which are commonly called seeds, although the true seed is contained within. The fruit is rarely more than 0.1 inch long. The seeds are among the smallest vegetable seeds. They are gray brown with five lighter, longitudinal ridges. A million seeds weigh slightly less than one pound.

After celery has produced a seedstalk, it is inedible. Commercially celery is grown from seed and harvested during the first season. Temperature can alter celery's normal growing habit. If exposed to cool temperatures (40 to 55F) for 10 days or more, celery may produce a seedstalk prematurely. This is called bolting. Increasing length of exposure to cool temperatures increases the likelihood of bolting. In a study reported by Thompson and Kelly, percentage of plants that bolted after varying lengths of time explosed to 40 to 50F were: 10 days, 7.6%; 20 days, 44.4%; and 30 days, 74%. Tendnecy to bolt is also genetically controlled as varieties have different levels of resistance to bolting. Conversely, lack of exposure to cool temperatures also affects celery's growing habits. According to Brown and Hutchison, "it is possible to inhibit seed formation by growing the plant continuously at temperatures 70F or above. In this way, normal biennial celery can be made to grow as a perennial.

The celery plant, before bolting, consists of roots, a short stem which might be an inch long, and a rosette of leaves. Each leaf is attached to the stem by an unusually long, fleshy petiole, which might be 6 to 15 inches. This is the edible portion. Leaves are pinnately compound having 5 to 7 leaflets. Leaflets are ternately (in threes) compound and often further divided or toothed. Foliage can be light to dark green in color. Those varieties which are yellow green are "self-blanching", while the dark green varieties are called "winter" celery. Winter types tend to mature later and are generally heavier and of better quality.

Celery produces a well-developed root system (consisting of a tap root and laterals) when the crop is grown from seed to market maturity without transplanting. When transplanted, the tap root is destroyed and the fibrous system is comprised of a large number of adventitious roots growing from the base of the plant. A large part of the root system occupies the upper 6 inches of soil many of the roots are within 2 or 3 inches of the surface, but some penetrate to a depth of 2 feet or more. Hence well-drained deep soils are preferred for its culture. Much of the celery is grown on muck and sandy soils for this reason.

Excerpted from Sackett, Clarice and Judy Murray [R.A. Seelig, editor]. 1977March. Fruit & Vegetable Facts & Pointers: celery. United Fresh Fruit & Vegetable Association, 1019 19th Street, NW, Washington, DC 20036.

Updated: Wednesday, May 23, 2012.