Cichorium intybus L.
Asteraceae (sin. Compositae)
History and origins
Wild chicory has been known for thousands of years: the ancient Greeks and Romans used it raw, as salad and attributed it with therapeutic properties among which, the capacity to treat insomnia; Pliny the Elder (23–79 CE), in his Naturalis Historia, emphasizes the herb’s purifying properties; Galen (129 – 210 CE) calls it a “friend of the liver”; Apicius (25 BCE-circa 37 CE), deemed the greatest gastronome of ancient times, in his De re coquinaria recommends serving wild chicory with garum (a fish sauce), onion and a little oil.
There are types of radicchio with red leaves and others with variegated leaves. Several sources believe that the radicchio cultivars derive from spontaneous red-leafed plants in the East that were then introduced into Europe in the XV century. The ancestor of all radicchio cultivated today is unanimously considered to be the red radicchio of Treviso, the result of a long selection process and improvements in production techniques.
The earliest reports regarding its cultivation in Veneto date back to the XVI century, but the production technique would only be refined towards the end of the XIX century. In fact, some sources believe that the blanching technique of the radicchio “Rosso di Treviso” originated with a Belgian nurseryman, Francesco Van De Borre. In 1870, he was commisioned with the creation of an English garden at a villa in Treviso and was attributed with having introduced the technique of blanching Belgian chicory (Chicory Brussels Witloof, chicory Witloof or Belgian endive, Chicorium endivia L.) to that area.
Other sources hypothesize, instead, that the “forcing” technique is due to the necessity of farmers in Veneto to preserve wild chicory picked in the fields and save it from the winter frosts.
The first exhibition dedicated to the producers of the Rosso di Treviso was organized in the interest of Giuseppe Benzi, an agronomist with Lombard origins, and held at the Loggia dei Grani in Piazza dei Signori in Treviso in December of 1900.
Fiber, besides regularizing intestinal function, contributes to the sensation of satiety during meals, thereby limiting the consumption of food with high energy density, and seems to play a positive role in controlling glucose and cholesterol levels in the blood.
Red radicchio is rich in anthocyanins (anti-oxidant flavonoids which give radicchio its red-purple color) which help decrease the risk of tumors and cardiovascular diseases, and have positive effects on urinary tract illnesses and on memory.
Diffusion and importance
Biologic type: wild chicory is an herbaceous perennial plant (perennating root) or biennial; radicchio is cultivated as an annual.
Root: taproot, with storage function, cone-shaped.
Stem: erect, with short internodes.
Leaves: the shape (more or less elongated), the prominence of the midrib, the color (dark red, wine-red, uniformly variegated red with white-green tones, creamy white with variegated purple) and the type of tuft (open or closed) vary accordingly to the type of radicchio (see “Varieties and/or commercial types”).
Inflorescence: forms during the second year, especially when stimulated by temperature and photoperiod. The hermaphroditic flowers, with light-blue petals, are clustered in single heads on a flowering stem, with bracts, very branched, up to 150 cm high. It is a mostly autogamous species (self-fertilizing) with a small percentage of allogamy (cross-fertilization).
Fruit: it is an achene (incorrectly called “seed”), with a pyramid-shaped pappus, of variable color (from cream to dark brown) and weight (1.0-1.5 g / 1000 achenes) depending on the cultivar.
Climate and soil requirements
Il Radicchio has moderate thermal requirements (see table).
It has good resistance to cold though this depends on the type: the Rosso di Chioggia and the Variegato di Castelfranco are the most sensitive to cold (the earliest cultivars can be damaged at just a little below 0° C); the Rosso di Treviso resists well to as low as – 5° C, and in fact, the cultivation specifications state that it must be harvested after having undergone at least two frosts, so as to favor the red coloring of the leaves.
However, drops in temperatures during the first part of the cycle must be avoided as they induce bolting and subsequent losses in product.
Il Radicchio is a hardy plant that is able to adapt to different types of terrain, though it generally prefers soils which are cool, deep and well-draining. In particular, the Rosso and Variegato di Chioggia prefer sandy soils; the Variegato di Castelfranco, medium-textured soil; the Rosso di Verona and Treviso are cultivated in clay to sandy soils.
In non-specialized agricultural firms, radicchio is a catch crop as it is sown or transplanted from June to the beginning of September after wheat, autumn-spring forage, corn to be ensiled and alfalfa.
In rotations, it follows strawberry, carrot, potato, celery, onion, cabbage, bean, spinach…
It is not to be replanted in the same soil.
Varieties and/or commercial types
Radicchio cultivation developed and was refined both technically and commercially in the Veneto region, so it is no accident that the various types of radicchio are named not only based on their leaf colors (red and variegated), but are also named after their places of origin and the cultivation of the ecotypes:
Rosso di Treviso, early variety: eaves characterized by a very prominent white midrib that branches out with many small, penninerved veins in the deep red of the considerably developed leaf blade; head is bulky, elongated, well closed, with a small portion of root.
Rosso di Treviso, late variety: elongated narrow leaves, wine red, with a very noticeable and completely white midrib; the leaves tend to close the tuft at the apical part; taproot is at most 6 cm long.
Rosso di Verona: slightly elongated leaves, roundish, dark red, with prominent midrib, curved upwards (resembling an upturned ‘cascade’ of leaves; very large taproot.
Rosso di Chioggia: spherical, bright red with thin white veins; small portion of root.
Variegato di Castelfranco: open tuft (rose-like); cream-colored leaves with streaks (from light purple to purple red to bright red) uniformly spread over the leaf surface; veins are not very prominent; taproot at most 4 cm long.
Variegato di Chioggia: spherical head, thick and fleshy leaves, variegated red with uniform white-green streaks.
Rosso di Chioggia, Variegato di Chioggia and Rosso di Treviso (early variety) have only one phase of cultivation in open fields: harvested plants are stripped of damaged outer leaves and immediately marketed.
Rosso di Treviso (late variety), Rosso di Verona, Variegato di Castelfranco: after their cultivation in the fields, harvested plants undergo a phase of post-harvest forcing: the cultivation in open fields produces plants with roots that are full of stored substances which are harvested, stripped of their leaves, and then subjected to a process (several forcing and blanching operations at adequate temperatures, with little light and humidity) so that they will sprout blanched, crisp and brittle leaves with a delicate and slightly bitter taste.
Rosso di Treviso, Rosso di Verona, Variegato di Castelfranco and Rosso di Chioggia have all obtained PGI (Protected Geographic indication) European certification status.
Far away from the traditional areas of selection and certified production, only early types of Rosso di Chioggia and Rosso di Treviso are cultivated.
Detailed information on standards of production can be found on the websites of the various PGI Associations for the Protection of Radicchio at the following addresses:
– www.radicchioditreviso.it : Consorzio di Tutela (association for the protection of) Radicchio Rosso IGP and Radicchio Variegato di Castelfranco IGP
– www.radicchiodiverona.it : Consorzio di Tutela di Radicchio Rosso di Verona IGP
– www.radicchiodichioggiaigp.it : Consorzio di Tutela Radicchio Rosso di Chioggia IGP
Fundamentals of cultivation practices
Il Radicchio can be sown or transplanted in rows 30-35 cm apart with a density of 7-10 plants per m2, depending on the variety.
The planting period varies, from June to the end of August, according to types and production areas.Fertilization and irrigation
Nitrogen requirements vary: they are high for Rosso di Chioggia (100-150 kg/ha) and low (60-70 kg/ha) for types to be blanched. In any case, nitrogen must not be distributed near harvest time (when planting and in the phase when plants have 3-4 leaves).
Irrigation is necessary, especially with loose soil and with dry, seasonal trends.Forcing of radicchio
Forcing is done for radicchio Rosso di Treviso, Rosso di Verona and Variegato di Castelfranco. In short, it is done in the following phases:
– Pre-forcing phase. Harvested plants, with 10-15 cm of taproot (according to the radicchio type), are stripped of outer leaves and cleaned of any remaining soil on the root. They are (separately or, if it is the Rosso di Treviso, in bunches) put into crates which are then put into furrows 20 cm deep and are, with well-ventilated tunnels, protected from rain and frost.
– Forcing and blanching phase. This is the most important phase. It is carried out by forcing the heads to sprout new leaves that, in conditions without light, will blanch and highlight the red areas, lose any fibrous consistency, become crisp and acquire a pleasantly bitter taste. The heads are positioned vertically into protected cement tanks and submerged up to the collar in spring water at about 11° C for 20-25 days, with little light. The plants are then brought into environments with a constant temperature of 18-20° C and put into layers of sand or other inert matters that can absorb water, until buds are completely ripe.
– Trimming. Leaves are removed, taproots are shortened and cut to a definitive length.
Radicchio is typically planted in summer and harvested in autumn-winter.
In the case of Radicchio Rosso di Chioggia and the opportune combination of varieties, areas of cultivation (the crop crossed the borders of its traditional Veneto area and is now cultivated in Fucino in Apulia and even Sicily) and means of protection (tunnels for northern cultivation of very early and late varieties in February-March and harvested in May-July), production has now become year long.
Even concerning the early variety of Radicchio Rosso di Treviso (which is not subjected to forcing and blanching), in the Center-South areas of the country, a certain interest in extending the period of production has been noted.
The other types of radicchio (the late varieties of Treviso, Verona, Castelfranco) remain, instead, in their traditional production areas, as they require solid specialization practices.
More specifically, the production and harvesting periods are as follows:
– Rosso di Treviso: from the beginning of September (early type) or from the beginning of November (late type) until the end of winter
– Rosso di Verona: from November to February
– Rosso di Chioggia: all year long (from the south, early types with summer production)
– Variegato di Castelfranco: from November to March
– Variegato di Chioggia: March-April
Harvesting is done by hand or, in large cultivations, even mechanically.
With radicchio types that do not have to be blanched, plants are cut at ground level; with types that have to be blanched, plants are cut 10-15 cm below their collars.