Start indoors or direct sow?

Start indoors and transplant for the most reliable results in areas with shorter growing seasons. Cardoon develops a substantial root system, so use roomy cells or pots and transplant while plants are still young.

When to start Cardoon seeds

Sow indoors about 8 to 10 weeks before your average last spring frost. Set plants outside after frost danger has passed and the soil has begun to warm.

How to sow the seeds

Sow seeds 1/4 to 1/2 inch deep in a sterile, well-drained seed-starting mix. Use deep 3- to 4-inch pots or large cells, then keep the trays warm in a bright setup.

Germination

Germination commonly takes about 10 to 21 days. Aim for soil temperatures around 65 to 75 F and keep the mix evenly moist, never saturated.

Seedling care

Give seedlings strong light for 14 to 16 hours daily, or place them in full sun after they emerge. Water at the base when the surface begins to dry, provide airflow, and avoid crowding to reduce damping off.

Transplanting & hardening off

Harden plants off over 7 to 10 days before planting them in full sun after the last frost. Plant at the same depth, water them in well, and allow generous spacing because mature cardoons are very large.

Tips

Do not let seedlings become rootbound, since oversized plants are harder to establish. In cold-winter regions, treat cardoon as an annual unless you can protect it through winter.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.