Parsnip

Description

Parsnip, Pastinaca sativa, is an herbaceous biennial plant in the family Apiaceae grown for its edible taproot resembling a pale carrot. The parsnip plant has an erect, branched stem with a rosette of leaves which are oblong or triangular in shape and 30–38 cm (12–15 in) in length. The leaves at the top of the plant are smaller and attached directly to the stem. The plant produces flowers on umbels which are yellow or orange in color with wide petals. The taproot of the plant is thick and fleshy and can grow between 10 and 23 cm (4–9 in) in length. The parsnip plant may grow to a height of 90–180 cm (35–70 in) in height and is usually grown as an annual for only one growing season. Parsnip may also be referred to as wild parsnip and originates from the Mediterranean.


Uses

The parsnip root is primarily eaten as a root vegetable after cooking. May be sliced and turned into crisps. The leaves of the plant are also edible and may be cooked and eaten as a vegetable.


Propagation


Basic requirements
Parsnips are cool-season crops which can be planted in early Spring and left in the ground all summer for harvest in the Fall or in the spring of the following year. Parsnips grow best in a well-draining, loose, sandy soil which is free of large rocks and has a pH between 5.8 and 7.5. Parsnips require full sun for optimum development but will tolerate some very light shade. The optimum temperature for their growth is between 15.6 and 18.3°C (60–65°F) and they do not tolerate heat in the same way that carrots do. The plants also require plenty moisture and organic matter. parsnips do very well in raised beds and can also be grown in containers.

Sowing seeds
Parsnip is usually direct seeded and should be planted 3–5 weeks before the last frost date. Soil should be prepared prior to planting by removing rocks and breaking up any hard lumps down to a depth of at least 30 cm (12 in). It is also beneficial to work some compost into the soil prior to planting. Avoid using fresh manure as it can cause forking of the roots. Sow seeds 1.3–1.9 cm (0.5–0.75 in) deep, planting 2–3 seeds per inch of row allowing 46–61 between rows. When seedlings reach 2.5 cm (1 in) in height, thin them to a final spacing of 5–10 cm (2–4 in) between plants by snipping with scissors - this avoids damaging plant roots.

General care and maintenance
Parsnips benefit from a plentiful moisture supply and should be provided with 2.5 cm (1 in) of water each week. Mulching around the plants helps to conserve moisture and reduce weeds. Plants can also be protected over winter with a thick layer of mulch Any weeds growing around the plants should be carefully removed. The plants should be fertilized 5–6 weeks after the seeds are sown.

Harvesting
For best results, parsnips should not be harvested until after the first light frosts in Fall, when the tops of the plants have frozen. Frost stimulates the conversion of starch in the roots to sugars giving the roots a sweeter flavor. Care should be taken to harvest before the ground freezes or to cover the plants to prevent freezing. Parsnips are harvested by gently digging around the plant to expose the top of the root and gently, but firmly pulling the root from the soil by grasping the top of the parsnip just above the root. Parsnip tops should be twisted off and the roots washed prior to refrigeration in airtight bags. Parsnips may also be stored in moist sand to keep them fresh prior to use.


References

Anderson, C. R. Parsnip. University of Arkansas Division of Agriculture. Available at: http://www.uaex.edu/publications/PDF/.... [Accessed 04 March 15]. Free to access.

Delahaut, K. A. & Newenhouse, A. C. (1998). Growing carrots, radishes, beets and other root crops in Wisconsin. A guide for fresh-market growers. University of Wisconsin-Extension. Available at: http://learningstore.uwex.edu/assets/.... [Accessed 04 March 15]. Free to access.


Common Pests and Diseases

Cavity spot
Pythium spp.

Symptoms
Sunken, elliptical, gray lesions across the root; outer layer of root ruptures and develops dark, elongated lesions; small vertical cracks may form on the cavities
Cause
Fungi
Comments
Fungi can persist in soil for several years and disease outbreaks are associated with wet soils; flooded soil increases the number of cavities formed
Management
Some cultural practices can control the disease: avoid planting in fields/areas known to previously had carrot spot; do not over-fertilize plants; application(s) of appropriate fungicide can provide adequate control

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

Itersonilia canker
Itersonilia perplexans

Symptoms
Small brown necrotic lesions on leaves with pale green halos; lesions may coalesce to form large necrotic patches; gray to black lesions on bases of petioles; red-brown cankers on root crown and shoulder with rough texture
Cause
Fungus
Comments
Disease typically emerges late in growing season and emergence is favored by cool, wet weather conditions
Management
The disease can be reduced by keeping the shoulder of parsnip roots covered with soil throughout the growing season; inoculum can be reduced by rotating crops, planting in well-draining soils, removing weeds and plowing crop debris into soil after harvest

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

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

Beet armyworm
Spodoptera exigua

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

Carrot rust fly
Psila rosae

Symptoms
Surface scarring of taproot caused by tunnels; tunnels are filled with a rust colored mush; adult insect is a small, dark colored fly; larvae are white maggots approximately 1 cm (0.3 in) long
Cause
Insect
Comments
Carrot rust fly also attacks carrot, celery and other Umbelliferous crops which will also need to be protected if carrot rust fly is a problem
Management
Use of row covers will help to protect plants from damage but they must be installed before adult fly lays eggs on plants; harvest parsnips in blocks; do not leave any parsnips in the ground over winter to reduce overwintering sites

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, parsley 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