How to grow cardoons – for a colossal ornamental edible that’ll catch the eye in any garden

Cardoons (Cynara cardunculus) are also known as artichoke thistles, and they are unique double-whammy additions to any space. Not only do plants offer spectacular architectural beauty, but they are also edible, with cardoon leaf stalks being popular in Mediterranean cuisine.

If you are looking for a striking plant for any flower bed, look no further than the cardoon. Reaching six feet in height, these herbaceous plants have silver-grey spiny leaves and tall flower stalks topped with thistle-like flowers, which attract pollinators.

You can grow cardoons as an annual or perennial, depending on your location, for a harvest of tender stems with a mild artichoke flavour. There is a skill to achieving the perfect harvest, which we’ll share here, along with tips for growing cardoon from seed and caring for plants throughout the season.

How to grow cardoons – a quick word of warning

There are many positive reasons for growing cardoons, as they are not only striking and bold additions to a space but also provide a harvest.

Growing cardoons is also an excellent choice for any wildlife garden, as their nectar-rich blooms attract a large number of bees and butterflies. They are also deer-resistant and rabbit-repellent plants due to their spiny foliage.

However, cardoons do self-seed in ideal growing conditions, which has led them to be classified as invasive plants in the warm climates of Argentina, Australia, and California. Check the status of cardoons for your location before planting or sowing.

Where to grow cardoons – planting tips

Cardoon can be grown as a perennial in US hardiness zones 7-10. Ashleigh Smith from True Leaf Market explains that 'cardoon is not a cold-hardy crop', but this does not mean it is not possible to grow in cooler climates.

'It should be grown where winters are mild, as this perennial is native to the western and central Mediterranean,' she adds. 'In cooler zones, it may still be grown as an annual with proper planning.'

Growing the plant as an annual means you get the large stalks and foliage, but not the thistle-like blooms, as the growing season isn’t long enough. However, you do still get the harvest of leaf stalks.

'Growing cardoon is simple and easy when done under the right growing conditions,' adds Ashleigh. 'Cardoon requires full sun and warm weather to thrive. Grow in a location with well-drained soil and room to spread up to 4-5 feet.'

An ideal place to grow cardoon will get at least six hours of daily sunlight. The plant will tolerate partial shade but won’t grow as impressively. It will thrive in fertile, well-draining soil types, supplemented with the addition of compost or well-rotted manure.

Ashleigh Smith

Ashleigh Smith is the Managing Editor at True Leaf Market with a bachelor's degree in horticulture from Brigham Young University, Idaho. True Leaf Market is a nationally certified organic, non-GMO seed and horticultural company based in Salt Lake City, Utah.

How to grow cardoons from seed

You can find young cardoon transplants in garden centers or online to plant directly into the garden after the last frosts for your climate. Alternatively, a more budget-friendly way to get plants is to grow cardoon from seed.

Start seeds indoors 4-6 weeks before your final frost, sowing the small seeds a quarter-inch deep into small pots filled with quality potting mix. The seeds will germinate well at 70-80°F in a greenhouse or on a warm windowsill, provided the soil is kept consistently moist.

The seedlings need indirect light, and lots of it, so consider using grow lights to supplement natural light and prevent leggy seedlings. Harden off the young plants and transplant seedlings outside into the garden after the frosts, spacing each at least 24 inches apart.

How to grow cardoons – care tips

• Watering - When growing cardoons, it is important to keep the soil evenly moist, especially while the plant is establishing. When mature, a cardoon can be quite a drought-tolerant plant thanks to its long taproot. However, they benefit from regular deep watering during dry periods to ensure you have tender stalks to harvest. A lack of moisture causes stress, which in turn leads to pithy stalks. Mulching around plants with organic matter helps to retain moisture in the soil and provides nutrients.
• Feeding - The addition of compost before planting helps supply lots of nutrients. When growing cardoons as perennials, or in the absence of compost, apply a balanced fertilizer each spring to promote healthy growth at the start of the growing season. Supplemental feeding can be done with a nitrogen-rich feed (such as this NitroGreen water-soluble fertilizer at Amazon) every few weeks during the season, which will encourage lush foliage and stalks to harvest. Additional feeds throughout the growing season are especially beneficial in poorer soils.
• Staking - Cardoons can reach six feet tall. Taller varieties will require staking to prevent them from flopping, especially when laden with the large flower heads that can make them top-heavy. Providing sturdy supports is especially important in windy sites, as the plants are liable to fall over. Put stakes in place when the plants are young, such as these heavy-duty metal plant supports at Walmart, and loosely tie the stalks as the plant grows with soft materials, like this soft and flexible garden tie also at Walmart.
• Pruning - Ashleigh Smith from True Leaf Market recommends pruning cardoons to maintain the plant’s 'attractive vase shape'. She advises: 'Remove the older leaves from the base of the plant as they age. The leaves may simply be snapped off or trimmed with pruning shears.' As new growth emerges from the center, old foliage is liable to cover the ground and smother nearby plants. Removing it keeps the plant shapely and healthy and also prevents it from covering other plants. Taking time to prune off spent flower heads also prevents cardoons from self-seeding and spreading. Perennial plants will die back during winter, and you should cut the debris to around 12 inches from the ground.
• Overwintering - In zones 7-10, cardoons can overwinter by mulching the plant to protect the roots from any winter colds. 'When grown in cooler regions, try pruning the plant to about a foot tall and covering it with soil or compost to protect it from the cold winter conditions,' adds Ashleigh. 'Uncover in the spring. If it successfully survives, you may enjoy its thistle blooms in the second year.'

How to harvest cardoons

Cardoons are harvested for their leaf stalks. These stalks need to be blanched for 4-6 weeks ahead of harvesting to make them more tender and flavorful. This can be easily done once the plant reaches three feet tall by tying a bunch of leaves together or wrapping stems with cloth or burlap to exclude light.

In late fall, cut the blanched stalks near the base with a sharp knife. Discard the tougher outer stalks and keep the tender, inner ones. Cardoon stalks can be stored in a refrigerator for 1-2 weeks and do need to be cooked before eating.

FAQs

Should I deadhead cardoons?

Deadheading is advisable when growing cardoons. The seed heads can offer an architectural look and provide food for birds during winter. However, deadheading them tidies up the plant and limits the plant's self-seeding around the garden.

Can you transplant cardoons?

You can transplant cardoons when growing them as perennial plants, and the best time to divide plants and move them is in early spring.

There is often some confusion between cardoons and globe artichokes. The two plants have a similar appearance, but the main difference between them is which part is harvested for cooking. For cardoons, it is the stalks that are picked. But when you grow artichokes, you harvest the immature flower buds.