How to Grow Cardoons
Cardoons are an interesting and unique vegetable that can add flavor and visual appeal to any garden. Though not as common as many other vegetables, cardoons are worth getting to know. With some planning and care, it’s easy to grow cardoons successfully. In this guide, I’ll walk through everything you need to know to plant, grow, and harvest delicious cardoons.
Choosing a Variety
There are a few different varieties of cardoon to choose from. The main options are:
Giant Smooth Spanish: This early maturing variety produces large, silvery-green stalks. It has an upright growth habit and is an excellent choice for northern climates.
Ivory White Smooth: As the name suggests, this variety has creamy white stalks. It’s an early maturing, spineless cardoon that does well in zones 3-8.
Vert de Provence: This is a popular French heirloom variety. It produces particularly large, flavorful stalks over a long harvest period.
For the home gardener, Giant Smooth Spanish and Ivory White Smooth are good choices that offer reliable results. I prefer the Giant Smooth Spanish variety for its vigorous growth and suitability for shorter growing seasons.
When to Plant
Cardoons need a long growing season of 120-150 days. This means seeds should be started indoors in late winter or early spring, 2-3 months before the last expected frost.
Here is a general planting schedule based on USDA Hardiness Zones:
Zones 3-5: Start seeds indoors in February or March. Transplant outdoors in May.
Zones 6-7: Start seeds indoors in March or April. Transplant outdoors in late April/May.
Zones 8-10: Direct sow outdoors in late winter/early spring.
It’s important to time plantings so that cardoons mature during cooler temperatures. Hot weather can cause bitterness and prevent proper development.
Starting Cardoon Seeds
Cardoon seeds need light to germinate, so sow them just below the soil surface. Provide bottom heat of 70-75°F to speed germination, which takes 7-21 days.
Once they develop 4 true leaves, transplant seedlings into 4″ pots or cell packs. Grow them on at 60-65°F for 6-8 weeks before hardening off and transplanting outside.
Proper starting ensures healthy, vigorous transplants that will mature quickly once planted in the garden.
Cardoons thrive in full sun and need nutrient-rich soil with a pH between 6.0-7.5. Work aged compost into the planting area before transplanting.
Space plants 2-3′ apart in rows 3-4′ apart. Cardoons have a upright, clumping growth habit and need sufficient room to develop.
Water transplants daily for the first week to help them establish. Then provide 1-2″ of water per week, adjusting for rainfall. Proper watering is key during the growing season.
Caring For Cardoon Plants
Cardoons require diligent care to produce a quality harvest:
Weed regularly to prevent competition for nutrients and water. Mulching around plants helps suppress weeds.
Stake stems as they grow to prevent toppling. Tie stems loosely to stakes.
Provide nitrogen fertilizer monthly to fuel growth. Compost tea or fish emulsion are organic options.
Monitor for pests like aphids and thrips which can damage developing leaves and stalks. Use insecticidal soap as needed.
With attentive care throughout the summer, cardoon plants will grow rapidly and fill out nicely.
Blanching Cardoon Stalks
An important step in growing cardoons is blanching the stalks as they size up. This involves excluding light from the stalks to reduce bitterness and make them more tender.
Once stalks reach 1-1.5” in diameter, wrap them together and tie with twine. Then wrap stalks with cardboard, black plastic, or fabric row cover to block out light.
Leave stalks blanched for 2-3 weeks before harvesting. Check periodically and re-cover any exposed areas. Proper blanching improves both flavor and texture.
Depending on the variety, cardoons are ready for harvest 90-150 days from transplanting. Plan to harvest before a hard frost.
Use a sharp knife to cut stalks off at ground level. Trim off all leaves, then peel the tough outer strings from the stalks. The innermost tender white parts are what get eaten.
Cardoon stalks will keep in the refrigerator for 1-2 weeks. They can also be blanched and frozen for longer storage.
Enjoy this unique vegetable prepared roasted, braised, or added to soups and stews. Cardoons compliment rich, wintery flavors. With proper care, they deliver an abundant and tasty harvest. Let me know if you have any other cardoon growing questions!