Radicchio – An Italian Conquers Austria
In the spring of 2024, the Experimental Station for Special Crops in Wies, on the initiative of Andrea Pölz (Chamber of Agriculture of Lower Austria) together with the Italian radicchio breeder Andrea Ghedina (Smarties.bio), organized a technical seminar dedicated to radicchio.
It was therefore an opportunity to closely examine a total of 21 varieties. This Italian specialty was mentioned for the first time in the 16th century. It is assumed that the varieties o that time had a much lower percentage of red leaves compared to those cultivated today. It is a fact that these remained in the fields during the winter months and were only harvested in spring. At that time, they were mainly open varieties, without forming a head, which were only later selected to obtain closed heads. The varieties we know today originated in the 1950s thanks to breeding work. All radicchio varieties derive from common chicory, of the Asteraceae family. Through the selection of different traits, very diverse forms developed around the cities of Northern Italy. The type that most closely resembles the original form is the Late Treviso Radicchio, with its fleshy white stalks and a reduced amount of red leaf blade. The Early Treviso Radicchio already shows a higher percentage of red leaves and forms a head. From the selection of more compact plants came the Verona Radicchio, with its oval shape. Through further crossing, this time with endive (Cichorium endivia), the Variegato di Castelfranco was created. After decades of breeding aimed at obtaining denser and tighter heads, the Chioggia Red Radicchio was developed. In recent years, further selections have led to the creation of new varieties with yellow, pink, or fuchsia-colored leaves.
Cultivation
To ensure good plant development, seedling production is recommended. The ideal germination temperature is between 25 °C and 28 °C. Growing temperatures below 16 °C can induce vernalization in the seeds and young plants, causing premature bolting. The optimal time for transplanting is when the plants have developed three to four true leaves, i.e., after about 23–25 days. Planting density is similar to that of lettuce, and the nutrient requirement is medium: 140 kg of nitrogen, 30 kg of phosphorus, and 140 kg of potassium per hectare. Excess nitrogen leads to the formation of excessive bitter substances. Most common varieties require between 90 and 120 days from transplanting to harvest. However, there are both earlier and much later varieties (Table 1). It is important that late varieties are not transplanted too early, as this would result in more outer leaves, smaller heads, and, in the worst case, premature flowering. Frost resistance is higher in late varieties compared to early ones. Temperatures around –6 °C are not a problem for the former, and even if frost damages the outer leaves, the inner part can often still be successfully marketed.
Harvest
Maturity is reached when the heads are compact and show the typical coloration. Radicchio stores well. Here too, the rule applies: early varieties have a shorter shelf life than late ones. Only healthy and as dry as possible heads should be used for storage; some outer leaves can be removed shortly before sale. For short-term storage of 2–3 weeks, optimal conditions are around 4 °C with a relative humidity of 95–98%. Varieties with a 110-day or longer cycle can be stored for up to 3 months. In this case, it is advisable to leave a piece of root attached to the head and to harvest slightly before full maturity, i.e., when the central vein is still slightly green rather than completely white. The ideal temperature for this type of storage is –0.5 °C with a relative humidity of about 70%. However, the inner part of the head must not freeze, and the air in the storage room must circulate.
Chioggia Red Radicchio is characterized by its abundant red foliage and thin central vein. The leaves form a very compact head. This variety is also eaten raw in Italy, often as a colorful touch in mixed salads. In addition to the Red Chioggia, there are also speckled and lighter forms.
Unlike the round types of Chioggia, the Early Treviso Red Radicchio forms elongated heads with a white, fleshy central vein. This radicchio is consumed exclusively cooked or grilled in Italy. A specialty of Northern Italy is the forced Late Treviso Red Radicchio.
Some varieties of the Late Treviso Red type (“Botteniga”, “Cagnani” and “San Benedetto”) were uprooted for forcing: the outer leaves were removed, the roots cleaned of soil, shortened and placed in perforated crates. These were arranged on ebb-and-flow tables in a greenhouse, filled with water that was changed several times a week. In about two weeks, tender and delicate leaves develop inside the head, which are consumed as a vegetable. They can be eaten raw in salads, stewed as a side dish, or au gratin in the oven. The taste is delicate, with a slightly sweet note.
The Rosso di Verona Radicchio is oval or egg-shaped and significantly smaller than the Treviso or Chioggia varieties. In Italy, it is often used for risottos. Its broad white central vein gives it a crunchy texture, making it also suitable for raw consumption. In Austria, this type is still little known.
Alongside the Late Treviso Red, another variety has been cultivated, still completely unknown in our region: the Rosa di Gorizia. This is the “Voglia” radicchio variety, which does not form compact heads. After the first frosts, these plants were also uprooted with their roots and forced for 14 days as described above. The inner parts, grown in the dark, are white, while the small existing leaves take on a light red hue. The tender heart of the plant is consumed (see image), after removing the outer leaves. The table clearly shows which varieties reached maturity in a few weeks and which required longer. Contrary to expectations, most varieties completed their development more quickly than predicted by the breeders.
1 Vesuvio Cicoria Rossa di Chioggia 2 Scala Cicoria Rossa di Verona 3 Voglia Cicoria Goriziana 4-6 Cicoria Rossa di Treviso Tardivo 5 Sangria Cicoria Rossa di Treviso Precoce
Sources:
Pölz Andrea, FIBL, Bio-net: Guide to the Cultivation and Varieties of Radicchio, 2025
Smarties.bio: https://www.smarties.bio/en-eu
DIin Doris Lengauer,
Mag.a DIin Andrea Pölz