Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
What is Radicchio?
Radicchio (Cichorium intybus var. foliosum) is a perennial leaf vegetable related to chicory. It is often referred to as Italian chicory because it is most frequently used in Italian cuisine. It was developed in the fifteenth century in Italy but the familiar red vegetable is a much later introduction, thanks to the work of a Belgian agronomist who started blanching the vegetable by harvesting and storing it in water in a shed. The lack of light in the shed caused the plants to stop making chlorophyll which gives plants their green color. With the chlorophyll gone, the vegetable’s natural red coloring was revealed.
There are several varieties of radicchio. Each is named for the region of Italy where it was developed by local farmers. The most popular variety here in the US is Chioggia. It has a rounded head and deep red coloring. The heads range in size from the size of an orange to the size of a grapefruit. The Treviso variety has an elongated head and more white ribs. Less often seen is Radichetta which is more loose leaf.
No matter the head shape, radicchio has a distinct flavor: bitterness. It is usually eaten cooked and less often in a salad. Radicchio is used in dishes as diverse as risottos, strudel, and tapenade.
Is Radicchio Poisonous?
According to folklore, when the root is used as a substitute for chicory in coffee, it can cause blindness. There is no scientific evidence of this. What scientists have discovered instead is that the plants contain oils similar to the herb tansy which are good for getting rid of intestinal worms. Radicchio is used as a forage supplement for farm animals because it helps to clear their intestines of worms which cause illness and sometimes death.
How to Grow Radicchio
Radicchio is a cool season plant best grown in the spring or the fall. It is perennial but is usually grown as an annual. In zone 8 and warmer, if the head is carefully cut from the roots in the fall, the roots may survive winter to regrow another head in the spring.
It grows best in rich, well-drained soil and full sun. Consistent watering is key. 1 – 1 ½ inches of water each week is ideal. If the plants are allowed to dry out, the flavor will become too bitter. With consistent watering, the flavor will actually sweeten in the cooler weather of fall.
Also key is weeding. Keep your plants well-weeded. Weeds compete with them for water and nutrients. A thick layer of mulch will help keep the weeds down and the soil moist.
Plan on 5 – 6 plants per person in your family. Space them 8 – 12 inches apart in rows 12 inches apart.
How to Grow Radicchio From Seed
Radicchio is most often grown from seed. The seed can be direct sown in the early spring for a spring crop or late summer for a fall crop. In my New Jersey zone 6 garden, that means sowing either in March or August.
Sow the seeds ¼ inch deep in rows 12 inches apart. Germination should occur in 7 to 14 days. When your seedlings are 3 inches tall, thin them to 12 inches apart.
How to Blanch Radicchio
To achieve the characteristic red coloring, you will need to blanch your plants. Blanching means to exclude sunlight from the heads so that they lose their chlorophyll and their true red coloring becomes apparent. Start your blanching process 2 – 3 weeks before harvest. There are three ways to do it.
Use the Plant’s Own Leaves
An easy way to blanch the heads is to pull the outer leaves over the head and secure them with either string or a rubber band. Make sure that the outer leaves are completely dry. If they are wet or even damp, they will cause the heads to rot.
Use Flower Pots
Another easy way to blanch your radicchio heads is to cover them with flower pots. For this you will either need a lot of extra pots or just a few heads.
Build a Shade Structure
This method requires building materials and the skill to erect structures. Take two long boards and stand them on their sides between the rows. Lay a third board on top of the side boards to prevent sunlight from reaching the plants.
How to Harvest Radicchio
You can harvest individual leaves at any time. To harvest the heads, gently squeeze them. If they are firm, they are ready to harvest, usually 60 – 65 days after you sow the seed. Just remember – older heads are more bitter. Harvest all of your heads after a frost. Discard any frozen leaves.
When you are ready to harvest, use a sharp knife to cut off all of the plant above the soil level.
How to Store Radicchio
Store your newly harvested heads in a perforated plastic bag in the crisper drawer of your refrigerator. They will last up to 2 weeks, but it is best to use them within 1 week. Raw radicchio that has been sliced can be stored for up to two days in an air tight container in your refrigerator. Cooked radicchio will also last two days when it is refrigerated in an air tight container.
© 2020 Caren White