Radicchio: tips for planting, care & successful harvest
The Italian vegetable with a slightly bitter note is still very popular and extremely healthy. We will show you what to keep in mind when cultivating radicchio.
Radicchio (Cichorium intybus var. foliosum) is a well-known vegetable from Italy, which is mainly enjoyed in salads. However, the cultivation of this red leafy vegetable differs from lettuce, as it is sensitive to too low temperatures at the germination stage. Nevertheless, it is still possible to cultivate this Italian delicacy in cooler climate zones. We will tell you everything you need to know to have your radicchio thriving in your garden. You will also learn about the origin, suitable varieties, cultivation, care, harvest and other uses of this flavoursome vegetable.
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Garden salads belong to either the genus of Lactuca or Cichorium. Alongside chicory (Cichorium intybus var. foliosum), endives (Cichorium endivia) and sugar loaf radicchio (Cichorium intybus var. foliosum f. cylindricum) all belong to the genus Cichorium. Together with chicory, radicchio forms the special subspecies Cichorium intybus var. foliosum. Typical of these is the bitter taste caused by the bitter substance called lactucopicrin. The plant is also known as red chicory or purple chicory.
For a long time, radicchio was only cultivated in Italy and imported to the countries north of the Alps. Recently, however, breeding was successful in producing new varieties that also grow in cooler climates. The red leaves bring colour to our plates and further embellish our vegetable patches with their vibrant heads. Although radicchio is mostly used to spice up salads, it can also be fried or steamed. It is thought that due to the bitter substances and other constituents, it is very valuable in terms of nutrition.
Radicchio: origin and characteristics
The largest area for growing radicchio is still in Bella Italia, which makes perfect sense as this is the origin of most varieties. To this day, Northern Italy is still the home of the most diverse set of plants of this genus. For a long time, radicchio was cultivated exclusively in that region as they thrive particularly well there. The crop is so integral to the northern Italian towns of Chioggia and Treviso that the two most important radicchio varieties derive their names from there. Since about 1985, however, it has become possible to grow it outside the region, so today it is widely cultivated in Spain and France.
In the past, it was mainly grown as a biennial plant, today it is usually cultivated as an annual. It forms a strong taproot – a straight tapering root growing vertically downwards and forming the centre from which subsidiary rootlets spring. Depending on the variety it can develop a thick leaf rosette with a lettuce head that is either firm or loose. Also, some varieties grow either round or elongated. The leaves of the lettuce are typically red with a white marble pattern, but some are completely red, green or a shade of yellow. In more northern latitudes radicchio is generally propagated indoors and not sown directly in an open field, this reduces the risk of flowering without any head.
Radicchio varieties
There are many varieties of radicchio in Northern Italy. Some are protected by the region of their origin and may only be sold under the variety name if the cultivation has taken place in the corresponding region. In Italy, a distinction is made between two types: type A is sown from spring to summer and harvested in autumn. Type B is sown from late summer to autumn and has more limited hardiness. This type can be hibernated in the wine-growing regions, in a foil tunnel or under a fleece. The numerous radicchio varieties differ mainly in colour, shape and harvest season. In the following, we have listed some of the most well-known varieties.
Round radicchio
- ‘Rosso di Chioggia’: This variety has the typical round, dark red heads with white-ribbed leaves.
- ‘Indigo’: This variety also has a round head and dark red, white-ribbed leaves.
- ‘Palla Rossa’: This variety has round, small heads that shine in an appetizing red with white ribbed leaves.
- ‘Orchidea Rossa’: This radicchio variety has bright red leaves. The head is loosely opened.
Elongated radicchio
- ‘Di Treviso’: The growth of this variety is rather unusual, as it is particularly tall. The leaves are of a dark red shade with a white rim. Also, this variety is cold-resistant.
- ‘Granato’: This variety has an elongated head and deep red leaves with white veins. It is excellent for dipping sauces, creams or for topping and decorating bread.
Colourful radicchio
- ‘Galileo’: Yellow to light green radicchio; this variety has special pink and red spots. It is also characterised by its delicate, mild flavour and is highly recommended for salads.
- ‘Variegata di Lusia’: firm heads in light green; the taste is delicate and mild.
- ‘Rosalba’: This variety has light pink coloured leaves and is rather rare.
- ‘The Yellow of Trieste’: This variety has yellow-green, round oval leaves with a mild taste.
- ‘Cicorino verde’: This radicchio variety has green leaves.
Variegata di Castelfranco: a unique delicacy
The variety ‘Variegata di Castelfranco’, with its peculiar shape, originates in the municipality of Castelfranco Veneto in the north-east of Italy. Italians often prize this speciality for its mild aroma and great taste. The variety also differs from the classical radicchio in appearance, as its shape is more similar to typical lettuce. The leaves of ‘Variegata di Castelfranco’ are light yellow with red splashes of colour – this is probably what gave the variety its nickname “orchid salad”.
‘Variegata di Castelfranco’ is rich in vitamins and, according to nutrition experts, has a positive effect on digestion and blood formation. As demand is currently very high, this explains the exorbitant price of up to 15 euros per head of lettuce. Local traders in Italy sometimes charge a proud 12 euros per head for this highly sought-after radicchio variant.
Cultivating and planting radicchio
Radicchio is particularly sensitive in its juvenile stage. They require optimal conditions to grow. In the next section, we will tell you what to look out for when growing radicchio, when it is best to sow and plant correctly. You can also read interesting facts with instructions for growing lettuce in our article here.
When do you grow radicchio?
The cultivation of radicchio from sowing until its last harvest takes place between mid-March and early winter. Most importantly, remember to keep the plants indoors or under glass between mid-March and the end of May. The early varieties from the sowing period in mid-March are planted out under shelter from the beginning of June. At the end of June, the young plants sown in April are brought outdoors. The late varieties sown after the end of May can be planted out from July to the beginning of August.
Tip: The emergence of inflorescence is caused when the head formation stops. This is also known as bolting and usually results in off the emergence of a flowering head. This is often stimulated by cool temperatures and decreasing length of the day. Radicchio planted out too early are at higher risk of sprouting. For that reason, particularly cool years must be covered to keep the plants warm and to protect them from direct sunlight. Conversely, radicchio planted later is less likely to sprout, as it is usually consistently warm in late summer and the day length increases again.
Summary: When to plant radicchio
- Early varieties: plant seeds starting in mid-March, plant outside at the end of June. The beginning of June is possible under glass or foil.
- Late varieties: plant seeds starting around end of May, plant outside from July to beginning of August.
Where can you plant radicchio?
Radicchio is best grown in a sunny to semi-shady location. However, the full midday sun should be avoided. As is common in its native country, Italy, this vegetable also likes to stay as warm as possible. Loose, deep soil is ideal. This allows the deep taproot of the plant to spread well. Radicchio does not tolerate stagnant moisture; it tends to rot if the soil is too wet. The soil should be rich in nutrients, humus and slightly acidic. However, radicchio is a light feeder, so refrain from fertilising it excessively. Very poor soils can be enriched with a plant-based fertiliser with a long-term effect, such as our Plantura Tomato Food. These release their nutrients slowly to not cause an oversupply.
The ideal location and soil for radicchio cultivation:
- Sunny to semi-shaded
- As warm as possible
- Loose, deep, humus-rich soil
- Without water-logging
- Improve very poor soils with fertiliser with a long-term organic effect
Tip: Good planting companions in a patch with radicchio are beans (Phaseolus vulgaris), dill (Anethum graveolens), fennel (Foeniculum vulgare) or onions (Allium cepa). Less suitable are parsley (Petroselinum crispum ssp. crispum), radishes (Raphanus sativus var. sativus) or celery (Apium graveolens).
How is radicchio cultivated?
Sowing is a critical step in cultivation because young radicchio is particularly sensitive to cold. We, therefore, recommend sowing in a greenhouse or inside on a windowsill. First, prepare pots of low-nutrient growing soil such as our low-nutrient Plantura Organic Herb & Seedling Compost. Next, place two to three of your seeds inside at a depth of one to two centimetres. Lightly sprinkle with soil and gently ensure everything is well moistened. Ensure that the temperature in the room never falls below 17 °C. Temperatures around 22 °C are even optimal. In a bright location without direct sunlight, the seeds should begin to rise within ten to fourteen days. When the first germinating seedlings have formed their first real leaves, the plants are ready to be relocated to larger pots. Choose the healthiest and strongest plants at this stage.
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Summary: How to grow radicchio
- Prepare the pots for growing radicchio with some soil
- Place the seeds into the soil at 1 – 2 cm depth
- Cover with soil only lightly
- Water the seeds carefully
- Put a plastic bag over the pot or put it in a mini-greenhouse
- Place in a bright location
- Ideal germination temperature: 20 – 25 °C
- Germination period: 10 – 14 days
- Transfer the strongest plants to a bigger pot when the first real leaves appear
The young plants can be moved outside when temperatures outside constantly begin to remain above 17 °C. For planting, keep a distance of 30 centimetres between each row. Prepare planting holes about 25 to 30 centimetres apart digging no deeper than the pots the plants have been inside so far. Loosen the surface soil in the area of your garden you wish to plant. Now you can place the radicchios in the planting holes and fill them with soil. Finally, water all of the plants thoroughly.
Heavier soils will need to be dug a little deeper. Remember to remove weeds and stones from the soil. Depending on the quality of your soil you may need to consider our Plantura Tomato Food. Due to the large proportion of organic ingredients, it can provide an excellent and steady supply of key nutrients for poor-quality soils and contributes to the formation of important humus.
Tip: How about combining radicchio cultivation with other plants between the rows? This way you can optimise the space and the soil is better protected. Onions or dill for example make excellent choices for neighbour plants. Both grow rather upright and will not hinder your radicchio.
Planting radicchio outdoors:
- Loosen the garden bed on the surface, dig deeper with heavy soils
- Remove stones and weeds
- Improve very nutrient-poor soils with fertiliser
- distance between rows: 30 cm
- planting distance: 25 – 30 cm
- Only place plants as deep as they were in the pot
- Water carefully
- Optional: Sow bedding neighbours such as dill or bulbs between the rows
Tip: Take extra care when removing the plants from the pots. Radicchio forms long roots that should not be damaged.
Care: watering and fertilising
Radicchio does not tolerate drought during its growing period and should therefore be watered sufficiently in high summer. If your radicchio has already been fertilised at the time of planting with a long-term fertiliser such as our Plantura Tomato Food, further fertilisation during the growing period is no longer necessary.
How is radicchio best fertilised and watered?
- Basic fertilisation with Plantura Tomato Food during planting stage
- Water sufficiently and frequently
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Tip: Over-fertilisation of red lettuce can lead to rotting heads. Burnt leaf edges on lettuce can be a sign of excessive fertilisation with nitrogen. It is better not to use mineral fertiliser, but rather a primarily organic fertiliser.
Propagating radicchio
Those who want to produce radicchio seeds will have to be patient until the following year. Only then will the plants form one to two-metre-high stems with beautiful, light blue flowers. To enjoy this bloom and the seeds that later develop from it, you must ensure to hibernate your radicchio. It is best to protect it from the cold with a fleece or with straw.
When the flowers have wilted, remove the inflorescences completely and dry them upside down in a warm place. The seeds can then be easily removed after drying and stored in a cool, dark and dry place. You can then use the seeds in the year after that.
How do you propagate radicchio?
- Hibernate lettuce plants: protect them from frost with fleece or straw
- In the second year, the radicchio will blossom
- Allow flowers to wilt, cut off inflorescences completely and dry upside-down
- Remove the seeds and store in a cool, dark and dry place
Harvesting and storing radicchio
Radicchio is a typical autumn and winter salad. This is partly because the typical reddish colour is only formed when the temperature varies greatly between day and night. We recommend harvesting radicchio heads only from the months of October to November. This is when you can enjoy rich red lettuce leaves.
Tip: If you expect early frost, you can cover frost-sensitive varieties with a foil or fleece so that they are not damaged if it is too cold before harvesting.
Radicchio cultivation takes a long time. The lettuce heads are only ready for harvest about ten to twelve weeks after germination. To harvest, use a sharp knife and cut the head off above the ground. Alternatively, you can pluck off individual leaves to keep the whole lettuce fresh while still in the garden bed.
Even when harvested, radicchio can be stored for a long time. You can store the fresh red radicchio in the refrigerator for up to four weeks. If you would like to store the lettuce for even longer, it is recommended to harvest it with the root. In a cool and dry place, such as a cellar, this way the lettuce will keep for several months.
How is radicchio harvested and stored?
- For a rich red colour only harvest from October onwards
- First harvest: 10 – 12 weeks after germination
- Use a sharp knife for harvesting
- Cut the head of lettuce just above the bottom
- Alternatively, just pick a few leaves and harvest them again and again
- Harvested radicchio stays fresh in the refrigerator for up to 4 weeks
- Harvested with root, the lettuce lasts for several months
Radicchio: nutritional information and use
The lettuce is not only appreciated for its bitter taste but is also very low in calories and full of valuable nutrients.
100 grams of raw radicchio contains:
- 10 kcal
- 0,2 g fat
- 1.5 g of carbohydrates
- 1.5 g dietary fibre
- 240 mg potassium
- 1.5 mg iron
- 28 mg vitamin C
The bitter substances in the leaves have a positive effect on digestion. This is because the leaves contain plenty of inulin, which the body digests like fibre to stimulate the digestive system. Radicchio not only spices up salad dishes visually but can be used in many ways. Enjoy radicchio baked, charred or pickled. Italians enjoy the leaves as a grilled side dish with meat, in pasta or risotto. Did you know that during the war, radicchio and other chicory plants were also used as a coffee substitute? The bitter taste was intended to recall the tart notes of roasted coffee beans.
Today radicchio is considered a delicacy. Those who do not appreciate its bitter taste combine it with sweet fruit, such as oranges or pears, or briefly soak it in lukewarm water. If you then remove the leaf veins, it tastes much less bitter. Longish varieties are best suited for cooking.
Common pests and diseases
Younger plants in particular are a prime target and should be protected from slugs (Arion lusitanicus).
Occasionally, however, aphids (Sternorrhyncha) can attack the plant. In this case, natural plant protection should be used. Those who like to grow their vegetables usually also find it important to garden sustainably.
Another thing to be aware of is signs of over-fertilisation. This is usually visible by the rotting of the leaf heads. Leaf edge burn can also occur in nitrogen-rich soils or over-fertilisation.
In general, radicchio is considered robust and easy to cultivate, one that is sure to add a leafy delight to both your garden and salad plate.
