Cardoons are a vegetable in the same family as artichokes.
The plant is perennial, with silverish green leaves and stalks, and can grow up to 7 feet (2 metres) tall. Most stalks are straight, but the curved ones are the most desired. The stalks look like celery, with the ridges on them. The ridges are sharper, though. "Razor-like" even, say people who think cardoon is the devil's own weed. When the plant flowers, the blossom looks like a large purple thistle, 2 to 3 inches (5 to 7 1/2 cm) wide from spring to mid-summer. Occasionally, a plant will produce white blooms.
Cardoon is regarded as a nuisance weed in North America. The plants have a deep taproot, down to 8 feet (3 metres.) They can infest an area very densely. Chopping a cardoon plant down repeatedly doesn't work; it just keeps growing back from energy reserves in its root. To deter wildlife from munching on it, it has tiny prickly spines on the leaves and stems, that can inflict painful wounds even though they are hard to see. Brushing up against one can make your arms look like they have a rash.
Ones being grown as an eating vegetable should be blanched as they grow. You pile soil up around the stalks as they grow, and when the plant is knee high, you gather up and tie up the outer leaves. Then, cover the lower 1 3/4 to 2 feet (50 to 60 cm) of the plant with black or dark green plastic, then cover the plastic with newspaper (to stop heat from turning the plastic wrapping into a small oven that cooks the plant.) Allow 2 to 4 weeks of growth in this way. Or, some wrap the plant with brown paper in spring and summer.
There is confusion between "lunghi" and "gobbi" cardoons. The two distinctions have nothing to do with different varieties or types of cardoons, but rather refer to cultivation practices. Gobbi is an Italian word that means "hunchback." What Italians do as the plant grows is bend the stalks down to the ground when young, and bury them in the earth. This blanches the stalks naturally, reducing bitterness and making them tender. English and American growers aren't familiar with this practice; they just let the stalks grow straight up.
If allowed to go straight up, Italians call them "lunghi." Though they have ways of dealing with the more bitter "lunghi", Italians naturally prefer to work with the ones grown as "gobbi", which even have some sweetness to their taste.
Ones grown as gobbi can sometimes be eaten raw.
In places where winter is mild, cardoons will continue to grow through the winter, but be woody and bitter by spring.
Cardoons can also be grown as an ornamental. Ornamental cultivars are bred with an eye to the most showy foliage and flowers, and not necessarily for the most tender stalks.
It is the stalks that are edible. The leaves can be eaten if at the end of summer, they are tied together and covered with dark plastic to blanch them, which softens them and whitens them.
Those who have had it grown and prepared properly say the taste is like that which comes from the tenderest part of an artichoke heart, the taste that you never get enough of when eating artichokes.
Most other people can't stop talking about the bitter taste. Though younger stalks are less bitter, you still have to par-boil them before you put them in stew to leach some of the bitterness out. Some people think they are just horrible, stringy, nasty and evil plants. They say by the time you've leeched out all the bitterness, and boiled the bejesus out of it to make it tender, you end up with something that tastes vaguely like overboiled artichoke.
Cardoons are often used as a dipping item in the Italian dish called "Bagna cauda." For use in this, it's simmered until just tender, drained, and plopped into ice water to keep it firm.
Cardoons are popular in France, Italy, Spain and North Africa. They were popular in England during Victorian times.
Italians often fry them in batter. Some people in France believe that boiling Cardoon with a large piece of bread helps remove the bitterness. In Provence, France, Cardoon is served on Christmas Eve in an anchovy and garlic sauce.
An extract made from dried Cardoon flowers can be used instead of rennet to curdle milk for cheese. This is used for instance in Azeitao cheese (Portuguese), and Queso de La Serena (Spanish.) The extract is not as strong as calves rennet, so curdling happens more slowly and can produce a creamier-textured cheese. It can also give the cheese more of a tang.
Very young Cardoon flower buds can be pickled in spiced vinegar or brine (using spices such as silphium and cumin), in the same way that caper buds are.
One variety, "White Ivory" ("Cardo Bianco Avorio"), produces white stalks without the need for manual intervention to blanch it. This variety is possibly of Italian origin, owing to its name always appearing in Italian in seed catalogues.
Discard outer ribs (they are too tough.) Cut the inner ribs into 3 inch (7 1/2 cm) slices. Pop in water containing vinegar or lemon juice to stop them from browning.
If the stalks are young, they will be tender and can be eaten raw or used directly in a recipe.
Use a vegetable peeler to clean off prickles, small leaf "ruffles", and ridges, before cooking.
Many recipes suggest an initial boil of 15 to 20 minutes for older stalk pieces to both tenderize them, and to help leach the bitterness out. After doing this, drain, cool, and peel off and discard the fibrous strings from the skin.
Some people consider that an effective way of removing bitterness from very bitter cardoon is to boil it with a piece of bread, or in water that has a runny paste of flour and water added to it, plus lemon juice.
To cook in a microwave, put the cardoon into a microwave-proof dish, cover with water, then cover the container (allowing hot air to escape.) Zap on full power for 5 minutes, then medium for 30 minutes. Test to see if it is tender to the fork. If you want it softer, continue cooking on medium for another 5 to 10 minutes (check water first.)
To steam it, just steam it until tender.
To deep-fry cardoon, steam or microwave it first, then drain it, then batter and deep-fry it.
To fully cook cardoon by boiling, it will take either 2 hours of boiling in a regular pot, or 50 minutes in a pressure cooker.
Freeze Cardoon only after you have cooked it until tender.
It was also introduced to Australia, New Zealand, and South America.