Stage 1 - field production
The root stage of the crop is grown for three to five months from mid-summer to autumn. The roots may then be forced over three to five weeks from autumn to winter but can be stored for up to 12 months at -1oC to 0oC. By this means, and use of the correct environment in stage 2, witlof may be produced throughout the year. In southern Western Australia, plants sown later than June may run to seed before digging.
Light, free draining soils, with a pH range of 5.0 to 7.0 (in calcium chloride), cultivated to 30cm, encourage straight root formation.
Hybrid white witlof varieties are usual but red varieties derived from radicchio are also marketed. These are smaller, sweeter and lower yielding than white varieties.
Sow seed into a well-prepared seedbed at a depth of 1-2cm, with rows 25cm apart and 20cm between plants. Thinning may be needed to give a spacing of 200 000 plants per hectare.
On sandy soils, apply a mixed NPK fertiliser throughout the life of the crop to ensure steady growth and high yield.
Immediately after planting (on the day of planting), broadcast 100kg/ha of a granular NPK fertiliser containing about 12% nitrogen, 5% phosphorus 14% potassium and trace elements. Continue broadcasting this product at 3-4 day intervals at 50kg/ha each time until day 21. Thereafter, step up the rate to 100kg/ha and continue at 3-4 day intervals until about day 35. From day 35 to until about 14 days before harvest, broadcast the same product at 125kg/ha per week.
Irrigate after topdressing to ensure that fertiliser granules lodged in leaf axils are washed out so that they don’t damage leaves and stems.
Irrigation
As witlof roots must be grown without moisture stress, the crop will require daily irrigation on sandy soils at most times of the year and twice-daily in hot weather.
Comprehensive information on the principles of irrigating vegetable crops in WA can be found on the vegetablesWA website. Irrigation rates and timing for your specific location and circumstances can be calculated by using the irrigation calculator.
No specific information is provided for this crop in the calculator but the guidelines for swedes can be used as a starting point.
Pests, diseases and weeds
The fungus Sclerotinia is the main disease likely. It causes the roots and witlofs to rot and is likely to infest land that has previously carried susceptible crops such as lettuce, beans, brassicas and potatoes. Close spacing and vigorous foliage growth increase the risk of Sclerotinia because of reduced air circulation.
Similar pests to those that attack lettuce can be expected on witlof foliage and African black beetle may attack the roots.
Hand weeding may be necessary in the early stages but as the crop covers the ground, it competes well with weeds.
The registration and availability of chemicals for pest, disease and weed control change regularly. Consult a trained and experienced horticultural agronomist or the Australian Pesticides and Veterinary Medicines Authority (APVMA) website for chemicals are currently registered or have a permit for use on this crop.
The information on the label or permit for a chemical must be followed, including directions for use, critical use comments, withholding period and maximum residue limit. Quality assurance (QA) schemes for horticultural crop production require producers to have current information on chemical registrations and permits readily available
Harvest
Roots should weigh about 100-150g at 20 weeks, with a diameter of 3-6cm. They can be dug by hand or with a converted potato digger after mowing off the tops.