Cardoon, a close relative of the artichoke and native to southern Europe, is mostly grown as an eye-catching ornamental in the United States but in Mediterranean cuisine, it is also used as a vegetable. Depending on the climate, cardoon is grown as an annual or a perennial. It starts out as a fast-growing, large, urn-shaped rosette with silvery, thistle-like leaves up to 3 feet long. Cardoon typically blooms in September or October and the growing season in areas with cold winters is usually too short for it to reach the bloom stage. But the foliage alone is striking so it is worth growing cardoon as an annual ornamental or for its edible stalks. The celery-like ribbed stalks may be blanched, steamed, or braised. The large, thistle-like, globe-shaped flowers are violet-purple and make striking, long-lasting flowers.
Cardoon Overview
Where to Plant Cardoon
Plant cardoon in a location with full sun. If you are planning to harvest the stalks, high soil fertility is key. For an ornamental, average soil will do. Cardoon grows in soil that is slightly acidic to neutral.
Cardoon needs plenty of room to spread and it has a deep tap root so it should be planted in soil that offers ample room for root development. The plant grows 5 feet tall or more, making it a stunning focal point in the back of a bed or border amid low-growing companions. You can also plant it in a vegetable or kitchen garden. Its bold, dramatic appearance makes cardoon a showstopper no matter where you plant it. If you have the space, plant a cluster of three cardoon plants to maximize its eye-catching appearance.
In some warm climates, such as in California, cardoon has become an invasive species. The plant aggressively self-seeds, which has led to the plant encroaching on wildlands. If you live in an area with mild winters where cardoon grows as a perennial and blooms every year, make sure to check that cardoon is not considered invasive. Even if it is not considered invasive, as a precaution, remove the mature flowers before they set seed and dispose of them in the trash.
How and When to Plant Cardoon
Start cardoons from seed indoors 6 to 8 weeks before the last average frost date in your area. Fill 4-inch pots with damp potting mix and plant 2 to 3 seeds in each pot, ¼ inch deep. Keep the pots at a room temperature of around 70 degrees F during the day and slightly cooler but not below 60 degrees at night. Spray the soil with water to keep it evenly moist. Once the seedlings emerge, they will need plenty of sunlight or grow lights, otherwise, they will get leggy. Thin to 1 plant per pot and remove the weaker seedlings, cutting them at the soil level.
Harden off the seedlings and transplant them in the garden after the danger of frost is past. Space plants 2 to 3 feet apart.
Cardoon Care Tips
Light
Whether grown as an annual or perennial, cardoon thrives in full sun with at least 8 hours of direct sun per day,
Soil and Water
Cardoon is adaptable to a variety of soil types, including sandy soil as long as it is deep and well-drained. Rich, fertile soil high in organic matter with a pH of 6.5-7.0 is ideal. Liberally adding compost, well-rotted manure, or other materials before planting will help produce bigger, healthier cardoon plants.
Because of its impressive taproot, cardoon is quite drought-tolerant. However, if you grow it as an edible, make sure it receives a constant supply of moisture. Under drought stress, the leaves and stalks become pithy and inedible.
Temperature and Humidity
While hardy in Zones 7 to 9, it prospers in climates with mild summers and winters, such as the Pacific Northwest. In a hot climate, cardoon is not long-lived. Heat also affects the taste. In hot weather, the stalks become unpalatably bitter but the taste will mellow again as cooler fall weather sets in. Protect cardoon from strong winds by planting it in a sheltered location. Mulch around the base to protect the root from the winter cold.
In climates with cold winters, cardoon is grown as an annual.
Fertilizer
Use a granulated all-purpose fertilizer for vegetable gardens and follow the dosage and frequency directions for annual or perennial crops.
Pruning
Prune damaged or diseased leaves any time. It is a good idea to remove the dead foliage that covers the ground around the plant, especially if it smothers surrounding plants. As new foliage emerges from the center of the plant, cut off the older, larger leaves to maintain a more vase-shaped plant.
Perennial cardoon dies back to the ground during the winter. In the spring, remove the debris to make room for the new growth.
Pollination
Cardoons are self-pollinating although the plants attract bees and other pollinators.
Potting and Repotting Cardoon
Due to its long taproot, growing cardoon in containers is not ideal, especially if your climate is mild enough to grow it as a perennial over several years. Also, the considerable height of the plant makes it likely to topple over.
If you want to grow it as an annual, use a container 1 to 2 feet in diameter and with large drainage holes. Keep in mind that potted plants need more water and fertilizer than plants in the landscape.
Pests and Problems
Cardoons are prone to be attacked by Japanese beetles and attract aphids, snails, slugs and blackflies. Powdery mildew is a common late-summer occurrence. More serious potential plant diseases, though rare, include gray mold and root rot, which is often caused by wet, poorly draining soil.
How to Propagate Cardoon
Cardoons are mostly propagated from seed as described under planting instructions above. Collecting seeds from your own plants is best if it is the species and not a cultivar, as those seeds won’t produce plants that are true to the parent. For cultivars, it is best to purchase seeds from a seed company.
Harvesting
When harvesting cardoons, blanching the stalks before the harvest requires an extra step but you’ll be rewarded with more tender, milder-tasting stalks. In the fall when the temperatures have consistently dropped below 70 degrees F, gently but firmly tie the stalks of the plant together with twine and tightly wrap the stalks with a thick layer of newspaper to keep the light out. Leave the wrap in place for 3 to 4 weeks.
Remove the wrap and cut the stalks at the base with a large, sharp knife. Remove the leafy growth; only the tender core of the stalks is eaten.
Depending on how long the cardoons continue to grow in your climate, you can keep harvesting them during the early winter.
Types of Cardoon
‘Porto Spineless’
This cultivar is grown for its culinary use but the attractive sharply lobed and serrated silver-green leaves are also used for flower arrangements. The stalks of this variety have been bred to have significantly fewer spines than the species. Zone 6 to 10
‘Gobbo di Nizza’
The name of this rare Italian heirloom variety of culinary cardoon means "hunchback of Nice." It has thick, almost spineless stalks and grows 6 feet tall with the flower heads so it may need support. Zone 6-10
'Tenderheart'
Grown mostly for its stalks but, with its large grey-green serrated leaves, this variety also doubles as an attractive ornamental. As a perennial, it grows over 7 feet in height so it may also need staking. Zone 8-10
Cardoon Companion Plants
Switchgrass
Switchgrass, a tough ornamental grass that stands up to a variety of harsh conditions, adds both texture and color to a garden. It spreads slowly over time and adds stunning vertical accents wherever it is planted. This warm-season grass blooms in mid to late summer. Zone 4-9
Dusty Miller
Easy to grow and long-lasting, dusty miller seems to thrive in almost any condition. Dusty miller is a tender perennial, similar to cardoon, it cannot be grown as a perennial below Zone 7 and it is therefore grown as an annual. With its low-growing silver foliage, it makes a good bedding plant. Zone 7-10
Coleus
Any coleus that thrives in full sun is a good companion plant for cardoon: edged-leaf, splotched-leaf, solid-leaf, or veined-leaf varieties. What all coleus have in common is that they are easy-to-grow annuals that need warmth and moist soil.
Garden Plan For Cardoon
Garden Plan to Soften a Fence
Here is a garden plan that uses a fence as a backdrop for a gorgeous bed of perennials and annuals blooming in shades of pink and purple. Most of the plants in this design are perennials, with a few bulbs and small shrubs mixed in for added interest. The result is a long-lasting garden that will require minimal maintenance year after year.
Frequently Asked Questions
- What is the lifespan of a cardoon plant?In a mild climate, a cardoon plant lasts up to 10 years. In cooler climates where cardoon does not survive the winter, it is grown as an annual.
In a mild climate, a cardoon plant lasts up to 10 years. In cooler climates where cardoon does not survive the winter, it is grown as an annual.
- Is cardoon the same as an artichoke?The two plants are closely related but different. Artichokes are a domesticated variety of Cynara cardunculus whereas cardoons are the wild form of that species. The kinship of the two plants is mirrored in the common name of cardoon, which is also called artichoke thistle, desert artichoke, or wild artichoke.
The two plants are closely related but different. Artichokes are a domesticated variety of Cynara cardunculus whereas cardoons are the wild form of that species. The kinship of the two plants is mirrored in the common name of cardoon, which is also called artichoke thistle, desert artichoke, or wild artichoke.