Starting Cardoon from seed is feasible, starting indoors for later transplant outside should commence 4 -6 weeks before the final frost date, transplant outside after hardening 3 to 4 weeks after the average last frost date in spring. If all goes well, it will be ready for harvest in roughly 120 - 140 days.
Germination Temperature at 65 -75°F.
Direct Seeding - sow 1/4 inch deep 12-16 inches apart
Thin out to 18-24 inches leaving only the best specimens
Row Spacing 36 to 48 inches apart.
If grown as an annual - spacing can be reduced somewhat as it will not reach its otherwise full potential
Height 3 - 4 feet
Spread 2 - 3 feet wide.
Full sun partial shade tolerable.
Soil - Well drained
Soil pH 6.0 to 7.0.
Evenly water allowing plants to dry out between watering. Water the ground and not so much the foliage.
Fertilizer - Cardoon has a high nutrient requirent when developing, fish emulsion bone meal and blood meal are helpful as are compost and well rotted manure which should be amended into the soil pre-planting. Side dress with a high nitrogen fertilizer.
Cardoon is at times targeted by aphids, spider mites and whiteflies if grown in a greenhouse. Artichoke Plume Moth will feed on Cardoon, but is rarely a major problem. Slugs have been reported to feed on the spineless varieties.
Harvest Cardoon buds before they reach full maturity for the best flavor. Harvest the stalks after blanching for at least a month. Blanching in this case is blocking out sunlight as described earlier, you'll also want to 'blanch' it in boiling water before eating it. Cut stalks off at ground level and trim away the leaves.
Cardoon stalks can be kept in the refrigerator for up to 2 weeks. It can also be frozen, canned, or dried. The stalks should be treated in the same fashion as celery.