Commercial Parsnip Production in Ontario

This infosheet was originally authored by V. L. Shattuck,formerly of the Department of Horticultural Science, University of Guelph; R.F. Cerkauskas, Agriculture Canada; and M. Valk, formerly of theUniversity of Guelph, Muck Research Station. It was reviewed by Janice LeBoeuf, Vegetable Crop Specialist, OMAFRA.

Table of Contents

1. Introduction
2. Soil Preparation
3. Planting
4. Nutrition
5. Weeds
6. Insects
7. Diseases
8. Harvesting
9. Storage

Introduction

The parsnip (Pasfinaca sativa) is a member of the parsley family which includes carrots and celery. Parsnips are native to Europe and Asia and were used by the ancient Greeks and Romans for medicinal and food purposes. Parsnips are biennial, but are grown commercially as an annual. The edible portion is the enlarged fleshy taproot. Although a majority of Ontario-grown parsnips are marketed within the province, some are also shipped into eastern Canada.

Soil Preparation

Parsnips are grown successfully on both mineral and muck soils. Muck soils are among the easiest to work and yield high quality roots. Parsnips are also ideally suited to loam soils. Heavier soils, where moisture cannot be controlled, are not the best for parsnips since it is harder to establish a good plant stand because of soil crusting. The soil depth should be at least 45 cm to facilitate the development of straight roots. Shallow soils may lead to forked or crooked roots. Good soil drainage is essential since waterlogging can result in crop failure.

Ontario parsnips are seeded in the field from April until mid-May. On mineral soils, a major problem in parsnip production is stand establishment. Careful attention should be given to preparing the seedbed.

The soil should possess a fine tilth and be free from clods and debris. Soil obstructions make seedling emergence difficult thereby leading to a more variable plant stand and may also result in misshapen roots.

Planting

Parsnips are planted in rows 45 to 75 cm apart with spacing between plants from 3 to 6 cm. To maximize yields, some growers use planters that scatter seeds thinly over a 5 to 8 cm strip rather than drilling seeds in a single line within the row. Thinning is seldom practiced due to the expense. The density of planting is important since this will determine root size at harvest. A few growers precision seed to ensure root uniformity and a lower number of culls.

The seeds should be planted at a depth of 0.6 to 2.0 cm. If the seeds are sown too deeply emergence will be reduced, and if they are planted too shallowly soil moisture necessary for germination may be lacking. In areas where winds are a problem, attempts should be made to protect planted fields from soil dispersal. Blowing soil may result in unevenly covered seeds which may lead to spotty stands (Figure 1).

Parsnip seeds germinate optimally when soil temperatures range between 10 to 21º C. In general, germination is slow even under ideal field conditions and where sub-optimal conditions prevail emergence may require more than four weeks. After germination, the soil surface should not be allowed to bake-out or the seedlings may be destroyed. Parsnip seed usually retains viability for only two years; thus it is advisable that growers purchase new disease-free seed each year from a reliable seed distributor.

To ensure continuous parsnip growth, consistent soil moisture is important. In muck soils the water table should be kept at 76 to 91 cm below the soil surface. Supplemental irrigation may be needed on mineral soils of low water holding capacity during arid intervals. If the soil is allowed to dry out for a period of time before irrigation, the developing roots may be prone to splitting.

Figure 1. Part of a field of parsnips grown on mineral soil near London, Ontario, subjected to severe winds prior to seed germination. Note the spotty stand and plants at different stages of development.

Nutrition

The nutritional requirements of parsnips are very similar to those of beets and carrots. An adequate supply of nitrogen, phosphorus and potash are important for optimal parsnip development. On mineral soils 110 kg/ha of nitrogen is recommended with 70 kg/ha applied preplant and 40 kg/ha side-dressed.

The amount of nitrogen applied to muck soils should be reduced to 60 kg/ha applied preplant. Nitrogen fertilization should be carefully monitored since excessive usage may result in rank foliage growth and increased susceptibility to diseases. If manure is applied or a soil-improving crop such as a legume precedes the planting of parsnips, the nitrogen requirements should be reduced (see OMAFRA's vegetable crop publications). Also, if manure is applied it should be well rotted before parsnips are sown. Fresh or non-rotted manures may cause deformed roots.

Phosphorus and potash requirements of the soil may be obtained through the appropriate soil tests (OMAFRA's vegetable crop publications). Parsnips may be susceptible to boron deficiency on new muck soils. In severe cases, boron deficiency may cause a breakdown in leaf and root tissues.

Weeds

Weeding is an essential operation during the first month after emergence. During early development parsnip seedlings are quite vulnerable to being crowded out by invading weeds. If hand or mechanical methods are employed for weed control the cultivations should be kept shallow or injury to developing feeder roots may result.

Insects

Principle pests of parsnips in Ontario include the carrot rust fly, carrot weevil, cutworms, flea beetles, leaf hoppers, nematodes and spider mites. The seriousness of these insects will depend on the location and year.

Diseases

Parsnips are subject to two major foliar and root diseases, Itersonilia canker and Phoma canker. An adequate spray program should be rigorously followed to control Itersonilia canker (see OMAFRA's vegetable crop publications). Spray applications typically start in early August, but may commence in July if the season has been wet. Phoma canker infection may result in substantial crop loss in the field as well as in cold storage. Grower experience has shown that crop rotation is important in parsnip production, especially in areas where Phoma canker and other diseases have occurred. Significant losses may be expected if parsnips are grown in soils where diseases have occurred the previous year. In recent years cavity-spot and/or horizontal lesions, which occur in carrots, have been reported in Ontario-grown parsnips. However, it appears that this problem is minor.

Harvesting

Parsnips are a long-season crop typically needing 110 to 130 days for maturity. However, in certain areas in Ontario, roots are lifted and sold after only 95 days.

Parsnips are harvested similarly to carrots. In the Bradford Marsh, in fields where excess foliage growth has occurred, some growers remove part of the parsnip tops during the season or prior to harvesting thereby facilitating harvesting (Figure 2). Roots are lifted by a carrot or modified potato harvester or in small plantings by hand. It should be noted that parsnip roots and foliage possess compounds which may induce inflammation of the skin. Thus, it may be necessary for certain employees to wear protective clothing when handling parsnips.

Figure 2. Parsnip Toper in the Bradford Marsh, Ontario.

Some parsnips are lifted in late August and sold fresh in Ontario. Most of the parsnips are harvested in October and November for winter storage. Some of the crop is left in the ground over the winter and then harvested in March through April the following year. Parsnip roots left in the field over the winter are very resistant to freezing injury. However, over-wintered parsnip roots will not tolerate soil thawing and freezing which may occur in April. Roots subjected to these conditions quickly lose quality and become cracked and pithy. Overwintered roots should be dug as early in the spring as possible before sprouting leads to a loss in root quality.

Storage

Sound roots may be kept in cold storage for 4 to 6 months at 0 C and 98 to 100% relative humidity. The sweet nut-like flavour of parsnips is not developed until roots have been exposed to temperatures near freezing; these temperatures normally prevail in late September and October. At low temperatures the starches in the root are converted to sugars.

Mature roots which have not been exposed to low field temperatures may be stored for two weeks at 0 to 1º C to develop flavour. Extremely low temperatures in storage may damage root tissues. Parsnips will freeze at -l.7º C. The centre of the core of frozen parsnips may become watersoaked with reddish brown areas developing in the cambium layer. The root may become externally dark brown after freezing, subsequent thawing, and exposure to room temperature for a short period of time. Parsnips should not be stored with ethylene-producing crops (e.g. apples), since the possibility exists that the ethylene may impart a bitter flavour to the root tissues.

During the winter months parsnips are periodically removed from cold storage, washed, sorted and usually packaged into 454 or 908 gram plastic bags for sale.