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Corey, K.A., D.J. Marchant, and L.F. Whitney. 1990. Witloof chicory: A new vegetable crop in the United States. p. 414-418. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Witloof Chicory: A New Vegetable Crop in the United States*

Kenneth A. Corey, David J. Marchant, and Lester F. Whitney

    1. Field Production Stage
    2. Storage
    3. Forcing
  8. Table 1
  9. Fig. 1
  10. Fig. 2
  11. Fig. 3
  12. Fig. 4


The United States currently imports approximately 2,340 t of witloof chicory (Cichorium intybus L.) valued at about $5 million annually The major exporting nations are located in western Europe, with Belgium in possession of the largest share of the U.S. market (Table 1). Recently, there has been considerable interest in the establishment of a domestic witloof chicory industry involving both field and forcing stages of production. Such an industry would provide economic opportunities for growers to produce on a year-round basis, a high value crop involving a recently developed adaptation of soilless crop production technology under highly controlled conditions. The objectives of this report are to summarize the management techniques established by European research on the crop while incorporating results of some of the work conducted in Massachusetts, evaluate the potential of witloof as a high value crop to U.S. farmers, and identify production and marketing constraints.


Witloof chicory, which is also known as Belgian endive by the general public, is a biennial herbceous plant belonging to the family Asteraceae. During the first year of growth, the plant develops a deep taproot and produces a rosette of leaves on a short stem. Following a period of cold exposure, the plant develops a floral meristem. Commercial production involves harvesting the plant following the attainment of a proper stage of maturity of the root, followed by floral bud induction (cold storage) and then an accelerated but controlled development of the floral axis and surrounding basal leaves in the dark (forcing). The end product of forcing is a chicon (Fig. 1), a small white head of leaves ringed with regions of yellow-green.

Related vegetables of commercial importance include lettuce (Lactuca sativa L., Cichorium tribe), the leafy salad vegetables referred to as endive and escarole (Cichorium endivia L.), radicchio (Cichorium intybus L.), and chicory grown for use as a coffee substitute (Cichorium intybus L.). In the U.S., the term endive usually refers to endive or escarole. While the common name Belgian endive helps distinguish it from the crops in C. endivia, it is not as descriptive as the common name witloof chicory which translated means "white-leaf" chicory. Some operations have combined the two common names and use the name witloof endive for the purpose of making this market distinction. Hereafter, the name witloof chicory will be used.


Field Production Stage

Witloof chicory can be grown successfully on a wide range of soil types. However, poorly drained, stony and compacted soils should be avoided as these conditions may lead to poor taproot development and interfere with planting and harvesting operations. It is desirable to grow the crop in rotation with crops that leave low residues of soil nitrogen. For this reason, small grains such as wheat, barley, and rye which typically require lower nitrogen inputs than other crops are generally considered to be ideal rotation crops. Excessive residues of soil nitrogen are undesirable because they may lead to luxurious leaf growth at the expense of the desirable accumulation of dry matter in the taproot and also because it may lead to a poor quality forced product (loose and open chicons). Generally, experienced European growers plant witloof on a given area once every four years to ensure that levels of inoculum of pathogens such as Sclerotinia sclerotiorum, and Pseudomonas marginalis do not reach injurious levels.

Planting dates for the crop will depend on location and the potential for prolonged periods of exposure to soil temperatures below 7°C. In the northeastern U.S. planting should begin not earlier than the last week of May and can extend as late as mid-July For early plantings, we have observed both cultivar and plant spacing effects on the percentage of plants that produce flowering stalks. Later plantings avoid this problem and also would enable the use of double cropping systems with fall-planted small grains.

The crop is generally precision seeded in 38 cm row spacings on the flat or on double-row ridges spaced at 76 cm. Results of planing experiments in June, 1988 at the University of Massachusetts demonstrated that at least 70 to 75% singulation of the naked seed can be achieved using standard precision seeding equipment and the appropriate belts. This is important for the elimination or minimization of the high labor requirement for thinning. The objective in planting according to European production recommendations is to achieve a plant population of 200,000 to 250,000 plants/ha. Results of our work indicate that higher plant populations may be used without sacrificing yield. For example, at a plant population of 440,000 plants/ha, crown diameters reached a plateau of about 3 cm and percentage dry matter in the roots leveled off at about 23% (Fig. 2). Both of these characteristics are important as indirect indicators of maturity It is necessary for the roots to reach a suitable stage of maturity or "ripeness" in order to later obtain maximum yield and quality of the forced product. Results of harvesting roots of 'Bea' and 'Flash' 123 days from planting and forced following two weeks storage at 1°C produced high quality chicons weighing from 100 to 120 g. Later forcings resulted in greater chicon weights due to an increase in the soluble sugar fraction resulting from the breakdown of inulin during storage. European growers consider roots possessing crown diameters of 4 to 5 cm as optimum for high yields and quality when grown at populations of 200,000 to 240,000 plant/ha and harvested 120 to 160 days from planting, depending on cultivar. Prospective U.S. growers will need appropriate recommendations for determination of the optimum time to harvest roots under their specific conditions. Studies in Massachusetts are currently in progress to determine optimum combinations of planting dates, plant populations, harvest maturities, cultivars, and forcing times.


Following harvest, the roots are placed into cold storage and held at 0 to 2°C and 95 to 98% relative humidity. During the first two weeks in cold storage, the vegetative bud differentiates to a floral meristem which then elongates during the forcing process. Also during storage, the storage carbohydrate inulin slowly breaks down leading to an increase in the soluble sugar fraction, a process necessary for growth and development of chicons during the forcing stage. The duration of storage influences the yield and quality of the forced product and is dependent on the cultivar and maturity status of the root. Generally, it is desirable to produce a range of cultivars that are suitable for early, intermediate, and late forcing to maximize yield and quality over the complete production cycle.


Forcing is the production phase with high value added and may be conducted using hydroponic methods or by conventional methods whereby a solid medium is used. Since the development and commercial application of hydroponic forcing methods has become a widespread means of producing this crop on a large scale, we have chosen to describe it here in more detail.

Using the hydroponic method, a crop can be grown to a harvestable stage in 20 to 25 days with forcing temperatures in the range of 13 to 22°C. The actual forcing temperatures used are dependent on maturity, cultivar, and duration in storage. Temperature adjustments are often necessary to increase or decrease, the rate of growth of chicons in order to produce the best quality product. For our studies, we have developed a modified and scaled down version of the large factory-scale systems (Fig. 3). Watertight trays generally 1 m2 are fabricated using wood or steel. A 4 cm outlet hole at the midpoint and as close to one edge as possible receives a telescoping plastic pipe fitting which can be extended downward into the tray below. Flow level in the top and succeeding trays is controlled by protruding the telescoping plumbing above the bottom to the desired level. This provides a 5 cm depth of flowing solution to the packed roots in the tray below. Sufficient headroom is provided to allow space for the chicons to grow. Stacking of the trays is such that the outlets are opposed to each other, thus providing a labyrynthian flow through the stack. Stacks are therefore in multiples of two trays and typically are 8 high, making for efficient utilization of vertical space.

The nutrient solution generally consists of three salts, Ca(NO3)2 at 0.45 g/liter, MgSO4 at 0.30 g/liter, and KNO3 at 0.88 g/liter. An upward drift in pH may occur during forcing attributable to the uptake of anions and efflux of hydroxyl ions and maybe monitored and adjusted periodically by additions of nitric or sulfuric acid to maintain a pH near 7.0. Nutrient depletion may also be monitored by measurements of solution conductivity and periodically adjusted by additions of fertilizer solution concentrates. Advanced forcing operations consist of computer assisted monitoring and adjustment of temperature, pH, solution conductivity and fertilizer injection.


Results of experiments from both field and forcing production stages indicate that witloof chicory can be grown successfully in Massachusetts and Connecticut. A major question that remains is whether high yields and quality can be obtained during years when high temperatures are encountered. Perhaps, it is more critical for cool temperatures to occur during the latter stage of growth when roots are accumulating dry matter at a high rate. Planting dates in Mid-Atlantic and Southeastern U.S. states could be as late as August, enabling cool temperatures during the latter stages of maturation and also enabling double-cropping systems with small grains to be used.

The economic implications of the factory-based hydroponic forcing systems are worthy of note. Fig. 4 shows a plot of roots per box (1 m2) and gross value of the chicons produced per box as functions of crown diameter. The calculation made to construct these plots assumes a wholesale value of $2.20/kg, 7.7 chicons/kg, and 80% marketable chicons. While these figures are crude and do not attempt to assess production inputs, the high potential gross return of the crop becomes clear when extrapolated to an area. For example, 5 cm diameter roots can be packed 400 to a tray as compared to slightly over 800 for the 3.5 cm diameter roots. The wholesale value would then rise from $90 to $180 per tray. Even if only 180,000 usable roots are produced per hectare very high returns would occur if all could be marketed. An economic analysis including production and forcing expenses needs to be prepared to determine the true value or profitability of this new crop enterprise.


The degree of success for witloof chicory to become a significant domestic enterprise is strongly dependent on marketing factors. Currently witloof chicory is considered primarily to be a gourmet item and the price it commands at the retail level makes it a vegetable that is purchased on an infrequent basis by the average consumer as a novelty. This is in contrast to the situation in France, Belgium, and the Netherlands where the crop is not as expensive and is consumed regularly during the winter and spring. For expansion of the U.S. market to occur, a combination of strong promotional campaigns and a moderate decline in price will be necessary. It is not likely that the price can decline to the point where it is competitive with other vegetable crops since two production stages and a storage stage are required. Given that increased consumer awareness of the culinary versatility of this crop leads to market expansion, opportunities for growers to produce this high value alternative crop will develop.

An additional marketing problem that may need to be addressed is the development of a retail pack that excludes light and the undesirable greening of the chicons, yet enables the consumer to view the product. This goal could be achieved by using a colored film that would exclude wavelengths of light necessary for chlorophyll synthesis at the top of the pack, with the remaining portion of the pack having the transparency necessary for consumer viewing of the product. The retail pack design could also incorporate the necessary gas permeability characteristics of the overwrap film to develop passive modified atmospheres, since witloof chicory has been demonstrated to respond favorably to lower oxygen and higher carbon dioxide concentrations.


The verdict on the feasibility of producing high yield and quality of this crop under a range of seasonal conditions will soon be established. At this stage, it is certainly a feasible and economically viable alternative crop available for some growers on a limited scale. An additional possible outcome of the transfer of the specialized technology used to force this crop is that it may be adaptable to producing other high value specially crops such as blanched asparagus. What remains to be determined, is the extent to which witloof chicory is accepted by consumers and consequently how much market expansion is possible. In conclusion, the future of witloof chicory as an alternative crop to U.S. farmers appears to be more limited by marketing factors than it is by production constraints.


*Paper No. 2903 of the Massachusetts Agricultural Experiment Station. Supported by funds from U.S. Department of Agriculture, Agreement No. 87-CRSR-2-3023.
Table l. Quantity and value of "witloof chicory imported by the U.S. from western European countries.

Quantity (t) Value ($)
Country 1985 1986 1985 1986
Belgium 1,865 2,189 4,016,839 4,555,125
France 23 26 50,535 39,955
Netherlands 158 151 376,835 402,281

Fig. 1. Carton of high quality, trimmed chicons forced hydroponically from roots of Cichorium intybus.

Fig. 2. Increase in crown diameter and accumulation of dry matter of roots of two witloof chicory cultivars during growth and development.

Fig. 3. Schematic diagram of forcing chamber adapted from factory scale systems used to evaluate treatments from experimental work.

Fig. 4. Generalized relationship of root packing density and projected value of chicons to root crown diameter. See text for assumptions and details.

Last update September 4, 1997 by aw