Apium graveolens L. var. dulce (Mill.) Pers.
Apiaceae (sin. Umbelliferae)
History and origins
It seems that its genus name, Apium, means “bee grass” in that it is a very melliferous species, though it may also suggest the Celtic root “apon” (water), referring to the fact that this vegetable prefers humid, boggy environments.
The name celery comes from the vulgar Latin selinum which derives from the Greek sélinon. Celery was regarded as the Greek plant par excellence and a symbol of prosperity.
Homer mentions wild celery in the Odyssey as a medicinal plant that grew in Calypso’s garden. In ancient Greece, celery was used to make up the crowns for the athletes who won the Isthmian and Nemean Games. It was consecrated to the Mother Goddess because it was linked both to the erotic and mortuary spheres.
For ancient Romans, wild celery (var. silvestre) had an important role in funereal ceremonies: they wove garlands and crowned their dead with it.
In the Middle Ages, it was regarded as an important medicinal plant because of its diuretic and digestive properties, as a tonic for the nervous system and as a stimulant for endocrine and especially, the suprarenal glands.
Its has been used in cooking since the XVII century.
The first golden, self-blanching celery was grown near Paris by a gardener, M. Chemin, in 1875.
Celery contains an aromatic substance, sedanolide (with the typical scent) and other phytoactive compounds (phenol, mannite, inositol) that help digestion and gas absorption in the digestive system.
It also contains phtalides, aromatic compounds of phtalic acid, that regulate blood pressure, so helping treatment of hypertension. Besides, celery contains various types of polyphenols with anti-inflammatory, antibacterial and antiviral properties.
Consumed raw, fresh or juiced (also centrifuged) it counters water retention thanks to its high diuretic capacity.
Diffusion and importance
Italy is the first European producer (about 40% of continental production), followed by Great Britain, Spain and France.
Cultivations are mostly in Apulia (about 23%), Piedmont (19%), Latium (10%), Veneto (6%) and Emilia-Romagna (6%).
The Apium graveolens L. species includes three botanical varieties with different food uses:
– var. dulce (Mill.): it is the common ribbed celery. We use the leafy stalks (“ribs”) that are long, thick, fleshy, green or golden yellow: consumed fresh, raw or cooked, or destined for the frozen-food industry;
– var. rapaceum (Mill.): it is the celeriac whose edible part is its enlarged, spheroidal, fleshy root that can be cooked or, more frequently, canned. Its leaves are much smaller than ribbed celery leaves; they have short petioles and an open disposition;
– var. secalinum Alef.: it is the Chinese celery (or “leaf celery”) whose tender and aromatic leaves regrow after being cut, and are used as seasoning.
Biologic type: celery is an herbaceous plant, biologically a biennal cycle, but annual in cultivation.
Root: sturdy, very branched, in most cases it explores depths of up to 0.4 m.
Stem: erect, with very short internodes.
Leaves: erect, 0.40-0.60 m long, made up of robust stalks (ribbed on the inner side, full, fleshy, green, yellow or whitish) and of pinnate leaves (pinnatisect, with serrated, lobed edges, bright green). The central leaves, tightened around the central apex, form a dense, etiolated center which constitutes the finest part of the vegetable, commonly called the celery “heart”. The plant has a natural tendency to sprout axillary buds that damage its appearance and can therefore, depreciate the product, especially if it is destined for the food industry.
Inflorescence: in its second year, after celery has undergone a period with low temperatures around 5-7o C (vernalization), it produces a flowering stem, erect, branched, hollow, 0.5-1 m high, with cymose umbels and 6-12 stalks. Flowers are hermaphrodite, small, with white-greenish petals. Flowering happens in June-July. There is cross-fertilization (allogamous), with mainly entomophilous pollination.
Fruit: it is a diachene 1-1.5 mm long, ripens in July-August. One single achene (“seed”) has an oblong shape, brown color and is characterized, like other umbellifers, by five ribs on its upper, convex side; there are also many secretory ducts that release aromatic substances with a characteristic scent. An achene weights about 0.3-0.5 mg.
Climate and soil requirements
Celery is suitable for temperate climates. Its thermal requirements can be seen in the table.
Germination is a very delicate and difficult phase: in cold soil (early sowing in the field), it is very long (15-20 days) and incomplete while with optimal temperatures, it takes about a week. With high temperatures (> 22o C) but in the dark (certain nursery conditions), it is even slower and more incomplete because there is photodormancy induction. The plant is damaged by temperatures near 0o C and has zero vegetation around 5o C; its optimal temperatures are 15 to 22o C. It is sensitive to high temperatures (> 30o C) that hinder its vegetative growth and favor phytopathologies such as “pithiness” and “black heart”. Exposure to low temperatures (5-7o C) induces flowering during the first year (bolting), and temperatures of at least 20o C can restore plants that are not entirely vernalized to a vegetative stage. Regardless of varietal sensitivity to floral induction, bolting is also favored by nutrient deficiency, water imbalances, parasitic activities and pollution. Bolting usually promotes the formation of axillary buds, probably because the apex loses its dominance. Consequently, it is not rare to find on the market in May, greenhouse-produced celery with the development of a flowering stem and a number of buds, with obvious negative effects on the quality of the product. For all of these reasons, celery cultivation is typically in spring-summer while with out of season cultivation (autumn, winter or early spring), the risk of bolting is greatly increased.
Water availability is another essential factor in production; therefore, during spring-summer, irrigation is necessary.
Celery is able to adapt to different types of terrain, but the best production is in soil which is medium-textured, deep, cool, fertile, with a high level of composted organic matter, well-draining, with a pH level of 6-7. It does not appreciate very calcareous soil, but it does tolerate salinity.
It is a typical rotation crop with a spring-summer cycle; it should not be replanted in the same soil or alternated with other umbellifers for at least 2-3 years.
Varieties and/or commercial types
– green ribbed: they can be sold green or blanched;
– golden yellow ribbed: they do not need blanching.
A good celery cultivar must have the following characteristics:
* foliage with erect bearing, not too high, with a sufficiently dense “heart”;
* ribs should be semi-long or long, thick, round, smooth, not filamentous, full, easy to blanch (green types), with a long shelf life;
* resistance to pre-blooming;
* resistance to main parasitic adversities (viruses, septoria, cercospora);
* resistance to cold.
The cycle length varies (on average, 80 to 150 days from transplanting).
Many Italian areas have typical productions of celery: for instance Piedmont (Dorato d’Asti, Sedano Rosso – red celery – di Orbassano), Veneto (sedano di Rubbio), Umbria (sedano nero – black celery – di Trevi), Tuscany (sedano “Marconi” di Montevarchi), Latium (Bianco di Sperlonga).
In Piedmont, the provinces of Asti and Alessandria boast famous ancient traditions in celery cultivation. In the Po Valley in the province of Alessandria, it is cultivated almost exclusively under shelter, while in the province of Asti, all cultivation is in open fields. 95% of the cultivars are related to the Dorato d’Asti; among these are two local selections with especially fine characteristics: the “Rissone” and the “Giuseppe”, cultivated with a high density of plants in every unit to encourage their natural tendency to develop that typical golden color (tufts growing on the external sides of the units are less valuable because they are greener). The red celery of Orbassano derives from the purple celery of Tours, introduced into Piedmont at the end of 1600s by the duchess of Savoy, Anna Maria d’Orleans (wife of Vittorio Amedeo II of Savoy); the duchess liked this vegetable so much that she imported it from France.
The “black” celery of Trevi (Perugia) is so called because, if allowed to grow with no blanching, it is very dark and woody. The final product is a celery with white and very long ribs, with a very pulpy and tender heart and very decided taste.
The “red” celery of Orbassano and the “black” celery of Trevi are in the catalogue of endangered heritage foods of the “Ark of Taste”, Slow Food movement (www.presidislowfood.it).
The sedano Bianco di Sperlonga (Latina), with PGI (Protected Geographic Indication) certification, is shorter (about 20 cm shorter than other varieties) and more compact than the Dorato d’Asti cultivar from which it probably derives following the first cultivations in the ’50s. It is usually cultivated with a high density of plants and natural blanching.
Fundamentals of cultivation practices
The common planting technique for celery is transplanting. Direct sowing followed by thinning is technically possible and would produce better rooted plants, but its slow and difficult germination and, if hybrids are used, the high cost of seeds (approximately, one hybrid seed costs about 1 eurocent, one seed of a standard variety costs 30 times less) make this technique not advisable and rarely used.
In Italy, in open field cultivations, transplanting is carried out from the end of April to the end of June to have productions all summer long and partially in autumn.
Sheltered cultivations (in tunnels or greenhouses) have autumn-winter or end of winter-spring cycles, according to general temperatures and to heating availability/use.
In open fields transplanting is carried out in single rows 0.50-0.60 m apart, with a density of 6-8 plants/m2: generally lesser densities are used for the highest varieties (60-70 cm), sturdy and late, while the highest densities are used for early varieties, medium sized (50 cm) and with very compact foliage. In sheltered cultivations density is usually much higher (up to 14-16 plants/m2, according to the variety and to the type of celery desired) and rows can be up to 0.35 m apart.
Celery has high water requirements (irrigation is necessary) and high nutrient requirements (especially nitrogen and potassium).
Generally, nitrogen increases the plant vegetative vigor, with early and ample foliage development, indispensable to get plentiful productions; an excess of nitrogen, though, can induce pithiness and increases the nitrate content of the product.
Adequate availability of phosphorus is essential for a balanced vegetative growth and to increase precocity.
Celery is very sensitive to magnesium and boron deficiency. Magnesium deficiency manifests itself with chlorosis and necrosis, up to leaf falling; boron deficiency stops the plant growth and causes stem and rib cracks. Calcium is another very important element in celery nourishment, because its deficiency and low mobility are among the causes (together with too high temperatures, excess of ammoniacal nitrogen and high densities) of “blackheart” (rotting of central leaves).
Celery has to be hoed carefully during the first phases of its cycle, before the foliage closes the spaces between the rows, to control weeds and to maintain good aeration of the soil.
Hilling is almost always carried out to irrigate it from lateral furrows and to blanch its ribs.
With blanching, commercial value of celery increases: the aim is blanching at least 2/3 of ribs. Blanching can be done in different ways:
– joining ribs and leaves in a bunch, fastening them near the top, and hilling the soil around the plants leaving out only the foliar laminae;
– wrapping the plants in black plastic film, cardboard or straw.
Blanching should start 2-4 weeks before harvesting.
In large cultivations self-blanching varieties are often used; plants are also in narrower rows to favor the shading action of foliage.
There are also harvesting machines that cut the plants and then, on conveyer belts, direct the product to the depot, where final processing is carried out; these machines are not very common and are limited to large, very homogeneous cultivations, mostly for food industry.
Average production of celery is about 50 tons/ha, but productions of 70-80 tons/ha are very common, especially in sheltered cultivations.