Apium graveolens (PROSEA)
- Protologue: Sp. pl.: 264 (1753).
- Family: Umbelliferae
- Chromosome number: 2n= 22
- Apium dulce Miller (1768),
- A. rapaceum Miller (1768),
- A. lusitanicum Miller (1768).
- Celery, stalk celery, leaf celery, celeriac (En)
- Céleri-côte, céleri-branche, céleri-rave (Fr)
- Indonesia: selederi, saledri
- Malaysia: sadri, selderi, seladeri
- Philippines: kinchai, kinintsai, kinsay
- Cambodia: chii tang' 'aô, kiën chhaay
- Laos: s'ii s'aangz
- Thailand: khunchai (central), phakpum (northern), phakkhaopun (northern)
- Vietnam: rau cần tây.
Origin and geographic distribution
Apium graveolens occurs wild (var. graveolens) as a marsh plant throughout temperate Europe and Asia (water celery). Even before the Christian era it had been brought into cultivation, first as a medicinal plant, later for the leaves (leaf or cutting celery) which were used as a flavouring (var. secalinum Alef.). It was, however, only in the 16th or 17th Centuries that milder-tasting special forms were selected in France or Italy for use as vegetable: stalk celery with large, swollen petioles (var. dulce (Miller) Pers.), and celeriac with a turnip-like edible tuber (var. rapaceum (Miller) Gaudin). These forms became the most important in western temperate areas.
Celery has also a long history in China, dating back to at least the 6th Century. The Chinese celery most resembles the leaf celery (var. secalinum), which is also most widespread in South-East Asia. The vernacular names in South-East Asia indicate that celery was introduced from Europe in the western parts (Dutch-derived names in Indonesia and Malaysia), and from China in the eastern parts (Chinese-derived names in the Philippines).
Westerners use the leaves and petioles of stalk celery and the swollen tubers of celeriac mainly for soups and salads. Leaf celery is used as a flavouring, fresh or in dried powdered form.
In South-East Asia, leaf celery (including Chinese celery) is the most important type. It is eaten raw as well as steamed, and minced leaves are mixed through a variety of dishes.
Celery is sometimes specifically grown for its seed (e.g. in India), which contains a valuable volatile oil used in the perfume industry, both as a fixative and additive. The oil is also used for flavouring salt. The plant has several applications in traditional medicine, particularly as a diuretic and emmenagogue, and against dengue and rheumatism.
Production and international trade
There is a considerable production and international trade in stalk celery and celeriac among western countries. In Europe, leaf celery has been mainly replaced by parsley. In South-East Asia leaf celery is the main form, but no production statistics are available.
Leaf celery has a much higher mineral content than blanched stalk celery. It contains per 100 g edible portion: water 90 g, protein 2.2 g, fat 0.6 g, carbohydrates 4.6 g, fibre 1.4 g, ash 1.7 g, vitamin A 2685 IU, vitamin B1 0.08 mg, vitamin B2 0.12 mg, niacin 0.6 mg, vitamin C 49 mg, Ca 326 mg, P 51 mg, Fe 15.3 mg, Na 151 mg, K 318 mg. The energy value is 113 kJ/100 g.
The plant contains the glucoside apiin and a volatile oil consisting chiefly of terpenes, but the characteristic smell seems to be due to the lactone sedanolid. The camphor of the volatile oil is known as apiol. The weight of 1000 seeds is 0.3-0.5 g.
- Biennial, erect, copiously branched, glabrous herb, 25-90 cm tall, with a fusiform to tuberiform fleshy taproot, and rosulate leaves when young.
- Stem fistular, angular, strongly grooved and ribbed longitudinally.
- Leaves long-petioled (often only a sheath), simply pinnate or 3-foliolate; leaflets broad from a cuneate base, 2-5 cm × 1.5-3 cm, trilobate to tripartite, petiolulate.
- Inflorescence a compound, many-flowered umbel, sessile or short-peduncled, terminal or opposite the leaves; primary rays 5-15, 1-3 cm long; involucres and involucels absent; umbellules 6-25-flowered; flowers hermaphrodite, 5-merous, white to greenish-white; pedicel (secondary ray) 2-3 mm long; calyx teeth absent; petals 0.5 mm across.
- Fruit a schizocarp, splitting into 2 mericarps, each up to 1.5 mm long and with 5 light-coloured ribs.
Growth and development
Celery is biennial in temperate areas, but cultivated as an annual for the vegetative parts. The life-cycle can, however, be completed in a year, if the plant is subjected to low temperatures during development.
Germination and seedling growth are rather slow and it takes 2-3 months to reach a suitable size for transplanting. During the vegetative phase, the plant above ground mainly consists of leaves, the stem being very short. The stem elongates after vernalization, the terminals ending in compound umbels. The root system is quite restricted and superficial. Crop duration depends on type (longest for celeriac), cultivar, and market preference, but varies from 4-12 months. Celery is mainly cross-pollinated.
Other botanical information
It is most practical to distinguish in Apium graveolens 3 cultivar groups:
- cv. group Leaf Celery (var. secalinum Alef.): cultivated for the aromatic leaves. It has slender green petioles, and is closest to the wild form (var. graveolens);
- cv. group Stalk Celery (var. dulce (Miller) Pers.): cultivated for its strongly developed petioles, which are curved in cross-section and grooved on the external surface, with a distinct joint where the petiolules of the leaflets are attached;
- cv. group Celeriac (var. rapaceum (Miller) Gaudin): grown for the roundish turnip-like swelling, about 10 cm across, mainly derived from the hypocotyl, but also incorporating part of the taproot and stem.
Chinese celery most resembles leaf celery (var. secalinum).
The wild form of A. graveolens is a halophilous marsh plant and this explains the high water needs and good salt tolerance of the cultivated forms. The types of European origin are usually cultivated in the tropics at higher elevations. They are adapted to areas with monthly mean temperatures of 15-21°C. Exposure at the five-true-leaf stage to 5-10°C for a minimum of 10 days, causes bolting. However, there is seldom a problem of premature flowering in the tropics. The Chinese forms are more heat-tolerant than the European forms and can be grown in the lowlands. Both types can be planted in South-East Asia year-round.
Celery demands a moist, pervious, fertile, if possible slightly saline soil, with pH 6-6.8, well-supplied with organic matter.
Propagation and planting
Celery is generally propagated by seed, leaf celery sometimes vegetatively by division. Seed is small (2000-3000 seeds per g) and is sown by broadcasting on a nursery bed. It is slow to germinate and the small and delicate seedlings should be well-protected. Transplanting to the field takes place 6-10 weeks after sowing. Leaf celery is planted relatively closely at 10-15 cm × 10-15 cm. Celeriac and stalk celery need wider spacing (30-40 cm × 30-40 cm), and the latter is planted in 20 cm deep furrows to facilitate the blanching of the petioles by earthing-up.
Deep cultivation to a depth of 20-30 cm is recommended, in particular for celeriac (tuber development) and stalk celery (to facilitate earthing-up). It also allows the incorporation of organic matter. Large amounts of nutrients are needed for a good celery crop. The removal of nutrients in 20 t/ha of stalk celery is estimated at 75 kg N, 40 kg P2O5, 170 kg K2O, 50 kg CaO and 18 kg MgO. Celery is susceptible to certain physiological disorders. These can usually be remedied by 10-20 kg/ha of borax and 100 kg/ha of magnesium sulphate.
Celery is shallow-rooting, necessitating frequent replenishment of soil moisture. Cultivation must be superficial in order to avoid damaging the roots. Thus mulching the soil surface helps retain moisture and smother weeds.
For stalk celery, the process of blanching is started 3-4 weeks before harvest by earthing-up or by wrapping paper around the petioles. White succulent petioles develop in the tropics, but they remain much smaller than in temperate areas. There are self-blanching cultivars (they have reduced pigmentation and closed plant-type and must be planted at high densities).
Diseases and pests
Diseases of celery include early blight, caused by Cercospora apii, and late blight, caused by Septoria apiicola. These fungi are seedborne and can survive on plant refuse in the soil. Seed treatment and crop rotation are recommended practices. Erwinia carotovora, a bacterium causing soft rot of the petiole, is also soilborne, and requires crop rotation. Damping-off of seedlings caused by species of Pythium, Sclerotium and Rhizoctonia is common. Rhizoctonia solani is also reported to cause lesions and rot of the petioles.
Few specific pests have been reported on celery, apart from polyphagous insects such as aphids, spider mites, leafhoppers, whiteflies and leafminers.
Leaf celery (including Chinese celery) can be harvested by pulling or by repeated cuts. In commercial plantings in South-East Asia, the once-over harvest is most common. The plants are pulled when 20-40 cm high, 6-10 weeks after transplanting or 3-4 months after sowing. The plants can also be cut about 6 weeks after transplanting, and subsequently harvested at regular intervals for about half a year.
Stalk celery and celeriac take from 6-12 months to become harvestable. Stalk celery is usually cut below the surface of the soil, leaving the petioles attached to the base of the stem. Tillers or suckers and pronged outer petioles are removed.
Yields of about 10 t/ha have been reported for leaf celery or Chinese celery, harvested by pulling. 50 t/ha is a normal yield in Europe for leaf celery harvested by 3 successive cuts, the first after 3-4 months, the next 2 at monthly intervals.
Stalk celery has been reported to yield 25-50 t/ha in Malaysia.
Handling after harvest
The harvested product should be removed from the field as soon as possible, washed, packed and transported to the market. For long-distance transport it should be packed in scraped ice. Celery can be stored for about 1 month at a temperature near 0 °C at very high humidity. It should be isolated in storage, because it readily absorbs flavours from other produce. In some western countries, celery is processed by canning. In the United States, stalk celery is also dried and processed into celery salt.
Important germplasm collections are maintained by the Research and Plant Breeding Institute for Vegetables in Olomouc, Czech Republic, by the National Bureau of Plant Genetic Resources, New Delhi, India, by the Vavilov Institute of Plant Industry, Petersburg, Russia, by the Institute of Horticultural Research, Wellesbourne, United Kingdom, and by the Northeast Regional Plant Introduction Station, Geneva, New York, United States.
Breeding programmes are mainly aimed at improving stalk celery and celeriac, two types of minor importance in the tropics. In stalk celery, the major objectives concern the tenderness of the petioles, the self-blanching character of cultivars and disease resistance. Little systematic research is being done on leaf celery.
Leaf celery is an important commercial vegetable crop in South-East Asia and an important ingredient in South-East Asian cuisine. Stalk celery should not be promoted at the expense of leaf celery, because the latter has a shorter growing season, is easier to grow and has higher nutritional value.
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