Sow seeds ¼ inch (.6 cm) deep in a rich starting soil. For successful cultivation, follow these Imperial Star artichoke care steps: Start Imperial Star artichokes indoors 8 to 12 weeks before the final frost date. Artichoke is considered to be one of the ultimate vegetables. Imperial Star In colder areas with severe winters, you should grow Artichokes as annuals. Germination time for Imperial Star artichoke plants is 10 to 14 days. Provide seedlings with 16 hours or less of quality light for optimal growth. Maintain ambient temperature between 65- … If the seedlings become root bound, transplant to a 3- … At 3 to 4 weeks, feed seedlings with a weak solution of diluted fertilizer. How to Grow an Imperial Star Artichoke. Seed varieties found in this category are great for annual cultivation, and produce well in their first year.