Based on experience at Oregon State University in 1998, Emerald was about two weeks earlier than Imperial Star, and appears to need little, if any, vernalization. Emerald buds tended to be angular in 1998, which had an exceptionally warm summer. Two other artichokes that are grown from seed are Grand Buerre and Talpiot, developed in Great Britain and Israel, respectively. A purple globe artichoke, more tolerant to heat and cold and grown from seed, is the variety Purple Sicilian. Proper climatic conditions are extremely important in artichoke production.
Artichokes do best in a frost-free coastal area with cool foggy summers.
Under such conditions the plant receives the proper vernalization and the right climatic conditions throughout its growing period to produce compact, tender buds for an extended period. 1991 and 1992 research data from Virginia indicates that vernalization of about 1300 hours of temperatures under 50 F was adequate to completely vernalize Green Globe and Imperial Star. Grande Buerre and Talpiot did not flower even after 500 hours of chilling. As noted above, Emerald appears to require very little vernalization. In the Willamette Valley, late summer and early fall production should be targeted due to hotter mid-summer temperatures which may result in rapid flower stalk growth and poor quality.