Dill

Description

Dill, Anethum graveolens, is an herbaceous annual in the family Apiaceae grown for its leaves which are used as a herb. Dill is a very aromatic plant with an erect growth habit. It possess branching stems and fine, soft, fibre-like leaves which are arranged into an open cone and are blue-green in color. The plant produces yellow flowers on umbels which can be up to 16 cm (6 in) in diameter. Dill can grow up to 1.5 m (5 ft) in height and is an annual plant, surviving only one growing season. Dill may also be referred to as garden dill and its origin is no known, although it is believed to be native to the Mediterranean.


Uses

Dill leaves are used fresh or dry as a culinary herb. The leaves may be used to make tea. The seeds of the plant may be used as a spice.


Propagation


Basic requirements
Dill grows best in full sun in temperatures averaging 16–18°C (601–64°F). Dill can be grown in a range of soils but the plants will grow optimally in well-draining sandy loam which is rich in organic matter and has a pH between 5.6 and 6.5. Dill should be planted in an area that receives 6 to 8 hours of direct sunlight every day and that is sheltered from strong winds which can easily damage the hollow stalks of the plant.

Planting
Dill does not transplant well and it is therefore recommended to direct seed. Seeds should be planted in early Spring after all danger of frost has passed. Sow seeds 1.9 to 2.5 cm (0.75 to 1.0 in) deep, allowing 30 to 38 cm (12-15 in) between plants and 45 cm (18 in) between rows. It is common for dill to be grown between other plants such as onions. Stagger plantings by 2 to 3 weeks for a continuous harvest. Seeds usually germinate within 7 to 21 days depending on the soil temperature.

General care and maintenance
Dill is a hardy plant and can tolerate temperatures down to -3.8°C (25°F) once established, Dill plants require little water, usually irrigating once or twice a week is sufficient and one light application of fertilizer late in the Spring should be enough to sustain the plant for the entire growing season. If the plant is not sufficiently sheltered from wind, the plants will benefit from staking to prevent the hollow stems from snapping.

Harvesting
Dill is ready to harvest approximately 90 days after planting. Foliage can be harvested anytime but is most flavorsome just before flowering. To harvest the leaves simply cut the leaves at the stem or cut the stem a few inches from the soil line. Seedheads should be harvested 2-3 weeks after bloom before the seeds begin to change color. The seedheads can be hung up to finish drying.



References

CABI Crop Protection Compendium. (2008). Anethum graveolens datasheet. Available at: http://www.cabi.org/cpc/datasheet/3472. [Accessed 21November 14]. Paid subscription required.

Masabni, J. & King, S. (2010). Dill. Texas A&M Agrilife Extension. Available at: http://aggie-horticulture.tamu.edu/ve.... [Accessed 21 November 14]. Free to access

Oakley, A. & Drost, D. (2009). Dill in the Garden. Utah State University Cooperative Extension. Available at: https://extension.usu.edu/files/publi.... [Accessed 21 November 14]. Free to access



Common Pests and Diseases

Powdery mildew
Erisyphe heraclei

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

Damping-off
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
Cause
Fungus
Comments
Damping-off diseases favor conditions which slow seed germination; fungi can be spread in water, contaminated soil or on equipment
Management
Avoid planting dill 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

Cercospora leaf blight
Cercosporidium punctum

Symptoms
Small, necrotic flecks on leaves which develop a chlorotic halo and expand into tan brown necrotic spots; lesions coalesce and cause leaves to wither, curl and die
Cause
Fungus
Comments
Disease can be introduced through infested seed and spread by wind or water splash; symptoms usually occur on younger foliage first
Management
Plant only pathogen-free seed; rotate crops; plow crop debris into soil ofter harvest; apply appropriate fungicide sprays

Downy mildew
Peronospora umbellifarum

Symptoms
Yellow spots on upper surface of leaves; white fluffy growth on underside of leaves; lesions become darker as the mature
Cause
Fungus
Comments
Disease affects young, tender leaves; disease emergence and spread is favored by prolonged leaf wetness
Management
Plant pathogen-free seed; do not overcrowd plants; rotate crops with non-umbelliferous varieties

Armyworm
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
Cause
Insect
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

Aphids (Willow-carrot aphid)
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
Cause
Insect
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

Cutworms
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
Cause
Insects
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

Root knot 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
Cause
Nematode
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

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

Symptoms
Yellow and red leaves; stunted plant growth
Cause
Viruses
Comments
Disease transmitted by aphids; both viruses must be present to cause carrot motley dwarf
Management
Avoid planting dill in close proximity to overwintered carrot fields