155 Effect of Environment and Gibberellic Acid (GA 3 ) on Earliness and Yield of Globe Artichokes S. Goreta, L. Bućan and G. Dumičić Institute for Adriatic Crops and Karst Reclamation, Put Duilova 11 21 000 Split Croatia Keywords: Cynara scolymus L., early yield, stalk length, head weight, cultivar Abstract Artichoke production in Croatia is concentrated on islands and in coastal area with main harvest in spring time. The aim of this paper was to research the influence of different concentrations of gibberellic acid (GA 3 ) on earliness and yield of cv. Imperial Star. Research was conducted during two years on island (Jelsa, 42 o 59`N, 16 o 41`E) and in the coastal area (Opuzen, 42 o 50`N, 17 o 33`E). In both years planting was done on 28 September in Jelsa and 20 September in Opuzen. GA 3 in concentration of 0, 12.5, 25, 50, 75 and 100 ppm was applied on plants with 12 developed leaves. Growth of the head stalk, early and the total yields, and average head weight were evaluated during experiment. An elongation of head stalk was influenced by GA 3 application on both locations and in both years. The highest stalks were recorded with application of 75 ppm GA 3. Harvest beginning was most influenced by year and location of growing, even though greatest early yield was achieved with 50 ppm GA 3 . The total yield and average head weight varied depending on location and year of growth, but they were not affected by GA 3 . Although the influence of GA 3 on growth and early yield was noticed, the effect depends on the climatic conditions after treatment and during growth period. INTRODUCTION The commercial production of globe artichoke (Cynara scolymus L.) in Croatia is located in narrow Adriatic coastal belt and islands, with prevailing Mediterranean climate. The floral induction of seed propagated artichoke cultivars requires a period of about 250 hours at temperature below 7 o C (Foury and Pecaut, 1988), while Welbaum (1994) found that 85% of plants of cv. Imperial Star (IS) produced the heads after 205 h at less than 10 o C. In Croatian growing conditions the temperature requirements are fulfilled in early winter for bolting of IS, but the bolting started with prolongation of day duration, as pointed out by Basnizki and Goldschmidt (1994). Depending on the climatic conditions the harvest of autumn planted IS starts as early as the middle of April in Croatia, and depends more on spring climatic conditions than on transplant age or type (Bućan et al., 2000). The influence of gibberellic acid (GA 3 ) on earliness of globe artichoke has been known for a long time (Gerakis et al., 1969), and has been employed on commercial basis (Ryder et al., 1983). In globe artichokes GA 3 participates in the process of flower initiation and in the subsequent stages of stem elongation and inflorescence development (Basnizki and Goldschmidt, 1994). However, the effectiveness of GA 3 depends on stage of growth and development and on the rate of application (Elia et al., 1994). In addition, in seed-grown varieties GA 3 effectiveness depends on sowing date, sensitivity of cultivar and number of applications (Schrader, 1992; Elia et al, 1994; Mauromicale and Ierna 1995). Enhanced earliness on artichoke crops means a higher price on the market as well as prolongation of harvesting period in spring season, which is highly important on Croatian market where the early spring crop has the best price. The objective of this study was to evaluate whether the application of GA 3 on naturally vernalized plants could affect earliness, head stalk length, early and total yield and head weight under different environmental conditions. Proc. of V th IC of Artichoke Ed. F.J. Sanz Villar Acta Hort. 660, ISHS 2004