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Radicchio
What it is: Cichorium intybus var. foliosum, family Asteraceae.
Origin: Mediterranean Basin, Italy.
Characteristics: A biennial herbaceous plant, cultivated as an annual, with variegated leaves or in various shades of red, yellow, or pink; leaves can be long and narrow with an upright habit or rounded and overlapping, forming round heads. In the second year, flowering stalks appear, with intense blue corollas.
Growing cycle: From 55 to 150 days, depending on the type and variety.
Easy to grow, radicchio is the king of salads thanks to its unmistakable flavor and the beauty of its leaves, which in some varieties open up like a corolla. There is still time to sow it for a winter harvest, when it becomes even tastier after a few frosts.
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Soil preparation: Radicchio, with its taproot reaching 30–40 cm in length, requires deep soil preparation, loosening the ground with a garden fork without turning the soil clods. Then spread 1.5 kg of mature compost per square meter (or 1 kg of pelleted manure per square meter) on the surface and lightly incorporate it with a rake or tiller.
Sowing period: For autumn-winter harvesting, sowing is generally done between June and July in the North, and between late July and August in the South.
Sowing method: Sow radicchio directly in the field: on well-prepared soil, make parallel furrows about 1 cm deep and 40 cm apart using a stick. Distribute the seeds along the furrows, cover them lightly with soil, and, if needed, level the surface with a roller to ensure good seed-to-soil contact. Water with a fine spray immediately after.
Thinning: Seedlings sprout 2–3 days after sowing, and once they have developed 4–5 true leaves, thin them out, leaving one plant every 30 cm.
Weeding: Throughout the growing period, it is very important to keep the soil free of weeds with regular hoeing.
Irrigation: Water regularly, especially in dry weather. It is best to water early in the morning so that leaves can dry during the day.
Harvesting: Depending on the chosen type, radicchio is ready from 55 to 150 days after thinning. The right time to harvest is when the head is firm and the leaves are well packed. If harvested after a few frosts, its flavor improves: the cold reduces its characteristic bitterness, makes it crunchier, and intensifies leaf color. Cut the head about 2 cm below the collar and remove any damaged outer leaves.
Pests and diseases: Radicchio can be attacked by aphids, which can be controlled with soft soap or other organic methods. In hot, humid conditions with poor air circulation, fungal diseases like powdery mildew can develop; this can be controlled with foliar sprays of water and baking soda, repeated every 2–3 days.
Growing requirements
Climate: Radicchio prefers temperate climates, with temperatures between 15 and 20 °C, and sunny, well-ventilated locations. Late varieties tolerate light frosts and snow, resisting down to –4 °C.
Soil: Thrives in loose, deep soils rich in organic matter and free of water stagnation.
Nutritional needs: Prefers fertile soils; apply compost or mature manure before sowing.
Varieties
Closed head, rugby ball-shaped, with scarlet red leaves elongated like a sword blade – hence its nickname “Spadone.” The central rib is white and broad. Bitter in taste, it is best suited for cooked consumption: in risottos, grilled, or baked. Sow from early July in the North to early August in the South, with harvests from mid-October to December.
This variety has a pinecone shape, with a compact head and deep purple-red leaves firmly adhered to each other. Bitter and crunchy, it can be eaten raw or cooked and is even used in sweet recipes. Sow from early July in the North to late August in the South, with harvests from early October to February.
Also known as the “Rose” or “Edible Flower,” for its open head with cream-colored leaves speckled with red and serrated edges. After harvest, the leaves are usually opened by hand in water to give them their traditional corolla shape. It is generally sweet, with a slightly bitter aftertaste, making it versatile and popular in cooking: traditionally eaten raw in salads, but also excellent in fillings, sauces, and even desserts. Sow from early July in the North to mid-August in the South, with harvests from October to mid-February.
This variety has a compact, round head with whitish-yellow leaves and crimson-red veins. It has a slightly sweet, pleasantly aromatic flavor, ideal for salads, though also used stewed. Sow from late June in the North to mid-August in the South, with harvests from mid-September to mid-January.
A descendant of “Rosso di Verona” with distinctive red-violet veins bordered in white, maintaining the same pinecone-shaped head. Its fleshy leaves make it particularly suitable for raw consumption in salads. Sow in early August in the North and mid-August in the South, with harvests in January and February.
Oval-shaped head with a beautiful straw-yellow color and fleshy leaves. Highly appreciated raw in salads for its texture. Only mid-late varieties exist, sown in the first half of August in the North and mid-August in the South, with harvests in December and January.
Leaves are pink with varying shades of intensity, and the head shape resembles “Rosso di Verona.” Due to its color and fleshy texture, it is mostly appreciated raw. Sow in mid-August, with harvests from December to January.
How to grow it?
1)Preparate the soil
Loosen the soil with a garden fork without turning the clods. Incorporate the fertilizer with a rake.
2)Sow
In summer, sow along 1 cm deep rows, cover with a thin layer of soil, press with a spade or level with a roller, and water.
3)Thin Out
When the seedlings have 4–5 true leaves, thin them out, leaving one plant every 30 cm. Select the healthiest, most vigorous seedlings.
Trick
Grow it on raised beds
Radicchio is sensitive to waterlogging and does not thrive in water-saturated soils, as these prevent oxygen from reaching the roots, causing root asphyxiation. To avoid this problem, especially in poorly draining soils, Andrea Ghedina, geneticist and co-founder of the seed company Smarties.bio (www.smarties.bio), recommends growing radicchio on raised beds 10–15 cm above ground level: if 80–100 cm wide, they can host two rows. This ensures quick water drainage. To extend the harvest period, if nighttime temperatures drop well below zero, it is advisable to cover radicchio with non-woven fabric.