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 Cardoon?
Cardoon (Cynara cardunculus) is a relative of the artichoke (Cynara scolymus) and will cross pollinate with it. Ideally they should be planted at least 100 yards apart. Most of us don’t have that kind of space in our yards so most gardeners just grow cardoon or artichoke, but not both. Another good alternative is to prevent the plants from blooming so that they cannot cross-pollinate. A good choice would be to grow cardoon just for its architectural foliage and grow artichokes for their edible buds.
Both cardoon and artichokes are thistles and members of the sunflower family. Cardoon is native to the western and central areas of the Mediterranean where it was domesticated thousands of years ago. Wild versions of the plant still exist in the area.
The flower buds of cardoon can be eaten like artichokes although they are much smaller and spinier. It is the stems of the young leaves that are most often eaten. They are blanched by either hilling them (like leeks) or by being wrapped in black plastic, a common method used by farmers who are growing them as crops. After the stems are harvested, they are braised. They look like celery and taste like artichokes.
Cardoon is hardy in zones 7 – 10. In colder climates, they are grown as annuals. The plants are 3 – 4 feet tall and 4 – 5 feet wide. They grow in a vase shape with leaves that are silvery gray with jagged edges. They are quite striking so cardoon is often grown as an ornamental plant. They have received the Royal Horticultural Society’s Award of Garden Merit.
New leaves emerge from the center of the plants, while the older ones die around the outside. These dead leaves lay on the ground forming mats that smother weeds and surrounding plants. You will want to keep an eye on the dying leaves and remove them before they get matted. Deer do not bother these plants thanks to their fuzzy leaves and sharp spines.
Because this is a perennial plant, it will flower in its second year. The flowers grow on stalks that can be up to 6 feet tall. They are purple and look like thistle flowers. Bloom time is late summer. Cardoons don’t flower in colder areas because they die at the end of its first growing season when frost occurs. Pollinators such as bees love the flowers.
The buds can be used as a substitute for rennet in cheesemaking, producing vegetarian cheese. Rennet is curdled milk from a calf’s stomach. It has been used for thousands of years to make cheese. It curdles the milk which then becomes cheese. Cardoon buds contain enzymes which curdle milk like rennet does, making it a good alternative for animal based rennet.
How to Grow Cardoon
Cardoon needs full sun and well-drained soil. It grows best in places with cool summers and mild winters. Due to its size, grow it in an area that is sheltered from the wind to prevent the plants from blowing over. They cannot be staked because they grow in a rosette of leaves. There is no central stem to attach a stake to. Thanks to its long taproot, the plants only need an inch of water each week. The plants are quite tough and not bothered by disease. They can become infested with aphids. Use a hose to wash them off of the leaves.
How to Grow Cardoon From Seed
In warmer climates, you can sow your seed directly in your garden after your last frost but most gardeners start their seed indoors 6 – 8 weeks before the last frost so that they can get a jump on the season. Seeds should be planted ¼ inch deep. Germination is quick – as little as 1 week. You can transplant your seedlings into your garden after your last frost when the soil has warmed. In my New Jersey zone 6 garden, I wait until the end of May for both the soil and the nights to have warmed up. Plant your seedlings 2 to 3 feet apart. They will grow into large plants and need space.
How to Harvest Cardoon
Your plants will be ready for harvest in 120 days. 3 to 4 weeks before harvest when the plants are at least 3 feet tall, you can begin the blanching process. You can either hill them as you would leeks or you can wrap the plants with burlap up to 18 inches to prevent exposure to the sun.
You can begin harvesting the leaf stems after 4 to 6 weeks of blanching. Using a sharp knife or your pruners, cut the stems at soil level. Then cut off the leaves, leaving just the stems.
How to Store Cardoon
It is best to use your harvest as soon as possible but if you aren’t able to, you can wrap the stems in plastic and store them in your refrigerator for 1 to 2 weeks. You can also freeze the stems for use during the winter.
© 2020 Caren White
Penny Leigh Sebring from Fort Collins on January 18, 2020:
I have never heard of this before! It sounds delicious!