Coriander (Cilantro)

Coriandrum sativum

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Description

Coriander, Coriandrum sativum, is an erect annual herb in the family Apiaceae. The leaves of the plant are variable in shape, broadly lobed at the base of the plant, and slender and feathery higher on the flowering stems. It is a soft, hairless plant. The flowers are produced in small umbels and are white or very pale pink in color with the petals pointing away from the centre of the umbel longer than those pointing towards it. The plant produces an oval shaped fruit which is yellow-brown in color and contains two seeds. Coriander is an annual plant, surviving only one growing season and reaches up to 50 cm (19.7 in). Coriander may also be referred to as cilantro, chinese parsley or dhania and originates from the Near East.

Uses

All parts of the coriander plant are edible, but the fresh leaves and the dried seeds are most commonly used. Leaves and seeds are used fresh or dried as a herb in cooking.

Propagation


Basic requirements
The plant grows optimally in areas with damp, cool springs and hot, dry summers at temperatures between 17 and 27°C (62.6–80.6°F) depending on the variety. The plant can tolerate light frost but hot temperatures will cause the plants to bolt. Coriander grows best in well-draining soil and can be grown in sandy loam, loam and clay soils as long as there is sufficient drainage. The plants will grow best when positioned in full sun.

Propagation
Coriander is propagated directly from seeds and should be sown after the last frost. The seeds should be planted in a prepared bed by planting seeds 0.6 to 1.2 cm (0.25-0.5 in) deep allowing 5cm (2 in) between seeds and 30 to 38 cm (12-15 in) between rows. Plantings can be staggered to ensure a continuous harvest. The seeds should be kept moist.

General care and maintenance
Once the young coriander plants are established they require little water as the plants do not perform well in damp conditions. The plants should be kept free of weeds, particularly when they are young to prevent competition for nutrients. The plants will benefit from the addition of fertilizer during the growing season. Phosphorous and potassium often limit the growth of coriander whereas the demand for nitrogen is not very high.

Harvest
Coriander can be harvested 45 to 70 days after planting. Leaves can be removed from the outside of the plant when they have reached 10 to 15 cm (4-6 in) in length. Commercially grown coriander is harvested by cutting the entire plant at soil level or 4 to 5 cm (1.5-2.0 in) above the crown, The bunches are then secured with a rubber band or tied together with a twist tie.

Diseases

Aphids (Willow-carrot aphid) Insect Cavariella aegopodii

Symptoms

Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants

Comments

Distinguishing features include the presence of cornicles (tubular structures) which project backwards from the body of the aphid; will generally not move very quickly when disturbed; willow-carrot aphid will also attack parnip, carrot and celery

Management

If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use

Armyworm Insect Pseudaletia unipuncta

Symptoms

Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside

Comments

Insect can go through 3–5 generations a year

Management

Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae

Bacterial leaf spot Bacterium Pseudomonas syringae

Symptoms

Very small water-soaked spots between leaf veins which enlarge and turn dark brown to black; stems may have elongated dark streaks; inflorescences yellowing and turning brown and blighted; water-soaked lesions on fruit

Comments

Disease is transmitted through infected seed and can be spread by splashing irrigation water and rain

Management

Bacterial leaf spot is difficult to control; plant pathogen-free seed; avoid overhead irrigation; do not work with plants when they are wet

Carrot motley dwarf (CMD) Viruses Carrot redleaf virus (CRLV)
+ Carrot mottle virus (CMoV)

Symptoms

Yellow and red leaves; stunted plant growth

Comments

Disease transmitted by aphids; both viruses must be present to cause carrot motley dwarf

Management

Avoid planting coriander in close proximity to overwintered carrot fields

Cutworms Insects Agrotis spp.
Peridroma saucia
Nephelodes minians
and others

Symptoms

Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but will usually curl up into a C-shape when disturbed

Comments

Cutworms have a wide host range and attack vegetables including asparagus, bean, cabbage and other crucifers, carrot, celery, corn, lettuce, pea, pepper, potato and tomato

Management

Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically

Damping-off Fungi Pythium spp.
Rhizoctonia solani

Symptoms

Soft, rotting seeds which fail to germinate; rapid death of seedling prior to emergence from soil; collpase of seedlings after they have emerged from the soil caused by water-soaked reddish lesions girdling the stem at the soil line

Comments

Damping-off diseases favor conditions which slow seed germination; fungi can be spread in water, contaminated soil or on equipment

Management

Avoid planting in poorly draining, cool, wet soil; planting in raised beds will help with soil drainage; plant high quality seed that germinates quickly; treat seeds with fungicide prior to planting to eliminate fungal pathogens

Powdery mildew Fungus Erisyphe heraclei

Symptoms

Powdery growth on leaves, petioles flowers stalks and bracts; leaves becoming chlorotic; severe infections can cause flowers to become distorted

Comments

Fungus can spread long distances in air; disease emergence is favored by high humidity and moderate temperatures; infection is most severe in shaded areas

Management

Plant tolerant varieties; avoid excess fertilization; protective fungicide applications provide adequate protection; sulfur application can be used in infection occurs early in season

Root knot nematode Nematode Meloidogyne spp.

Symptoms

Galls on roots which can be up to 3.3 cm (1 in) in diameter but are usually smaller; reduction in plant vigor; yellowing plants which wilt in hot weather

Comments

Galls can appear as quickly as a month prior to planting; nematodes prefer sandy soils and damage in areas of field or garden with this type of soil is most likely

Management

Plant resistant varieties if nematodes are known to be present in the soil ;check roots of plants mid-season or sooner if symptoms indicate nematodes; solarizing soil can reduce nematode populations in the soil and levels of inoculum of many other pathogens

Soft rot Bacteria Erwinia carotovora
Erwinia chrysanthemi
Pseudomonas marginalis

Symptoms

Small water-soaked lesions near base of petioles which become soft, sunken and brown

Comments

Bacteria thrive in oxygen depleted plant tissue; disease emergence requires long periods of water saturated soil; bacteria enter plants through wounds

Management

Control relies on the avoidance of conditions conducive to bacterial infection: plant coriander in well-draining soils; allow plants to dry before irrigating again; avoid wounding plants during harvest to prevent pst harvest development of disease; disinfect all equipment regularly

References

CABI Crop Protection Compendium. (2008). Coriandrum sativum datasheet. Available at: http://www.cabi.org/cpc/datasheet/15300. [Accessed 14 November 14]. Paid subscription required.

Smith, R., Bi, J., Cahn, M., Cantwell, M., Daugovish, O., Koike, S., Natwick, E. & Takele, E. (2011). Cilantro Production in California. University of California Vegetable;e Research and Information Center. Available at: http://anrcatalog.ucdavis.edu/pdf/723.... [Accessed 14 November 14]. Free to access.

Miller, C. & Drost, D. (2006). Cilantro/Coriander in the Garden. Utah State University Extension. Available at: http://extension.usu.edu/juab/files/u.... [Accessed 14 November 14]. Free to access.