The globe artichoke (Cynara scolymus L.) is usually propagated vegetatively because plants grown from seed lack uniformity. Furthermore, in much of the United States, only a small percentage of plants grown from seed flower during the first season due to insufficient chilling for vernalization. Artichokes cannot be grown reliably as perennials without winter protection where temperatures are consistently below -10C. The new cultivars Imperial Star (IS) and Talpiot (TP) reportedly produce uniform plants from seed and a high percentage of flower heads (capitulum) the first year with minimal chilling. `Imperial Star' and TP were compared with the standard seed-propagated cultivars `Green Globe Improved' (GG) and `Grande Buerre' (GB). Plants of each cultivar were tested over a 3-year period in Blacksburg, Va., or for 1year in three other locations. Essentially all IS and GG plants flowered after receiving 1356 h of chilling at <10C. With 205 h of chilling, 83% of IS plants flowered compared to 25% for GG. No TP or GB plants flowered after receiving as much as 528 h of chilling. In the mountains of western Virginia, only IS plants established in the field in early May received sufficient chilling to produce flower heads during the late summer and early fall. June transplants did not flower because sufficient chilling was not obtained for vernalization. In warmer areas of central and eastern Virginia, fall establishment for spring harvest may yield a higher percentage of flowering plants compared to spring planting and summer harvest.
Gregory E. Welbaum
S. Husain and K. Stewart
This research is focused on developing production techniques for globe artichoke (Cynara scolymus L.) production in Quebec, Canada. It is a herbaceous perennial grown for its immature flower bud. The globe artichoke is usually propagated vegetatively because plants grown from seed lack uniformity. Furthermore, only a small percentage of plants grown from seed flower due to insufficient cold treatment for vernalization. Artichokes cannot be grown as perennials where winter temperatures are below –10°C. The objectives are to determine the optimum nitrogen fertilizer requirements, and irrigation levels, and to evaluate two widely grown cultivars. Globe artichoke was grown in the greenhouse from seed in March 1995. Seedlings were naturally vernalized and transplanted to the field in mid May on silver plastic mulch. A split-split-plot design was used with three replications. At the rate of 2.5 cm per week water was applied via drip irrigation to one half of the field and the other half received irrigation based on tensiometer readings. The nitrogen treatments were 100, 200, and 300 kg/ha of N of which two-thirds was incorporated preplant. The remainder was applied as a sidedress a month later. In this study, `Imperial Star' (IS) produced uniform plants from seed and a higher percentage of plants produced flower heads (bolted) than `Green Globe Improved' (GG Imp). The harvest period began on 1 Aug. for IS and 9 Aug. for GG (Imp). It ended on 18 Sept. for both cultivars. Eighty-six percent of the IS plants produced buds compared to thirty-nine percent for GG (Imp). Both cultivars produced a high percentage of small buds. Yield from plants that received 2.5 cm of water weekly was greater than the irrigation treatment based on tensiometer readings. Data on nitrogen treatments, days to flowering and harvest, flower bud quality, weight and size of terminal buds, and total yield are being statistically analyzed using SAS.
Stan C. Hokanson, Fumiomi Takeda, John M. Enns, and Brent L. Black
Tissue-culture derived mother plants were established in a greenhouse suspended-gutter, nutrient-film technique growing system to evaluate runner tip productivity in the system. Effects of cultivar (`Allstar', `Chandler', `Latestar', `Northeaster', and USDA selection B 27) and duration (0, 1, or 2 months) of cold storage at 1 °C on tip viability, rooting success, and performance in fruit production were determined. The average number and weight of runner tips produced in the gutter production system, the capacity of runner tips to form cohesively rooted plug plants, and the number and length of adventitious roots produced by runner tips varied significantly among the cultivars and the three storage durations (0, 1, or 2 months). In the field, plants produced from runner tips stored for 2 months produced more runners than plants produced from freshly harvested runner tips. Crown number differed among the cultivars, but was not affected by cold storage treatment. No treatment differences were noted for the fruit harvest parameters evaluated. The results suggest that the transplants derived from mother plants grown in a greenhouse-based soilless system can be useful for annual plasticulture strawberry production in colder climates. Although long periods of cold storage of runner tips resulted in lower tip-to-transplant conversion ratios, field performance of transplants was not adversely affected. Additional research is needed to improve greenhouse strawberry production practices for increasing runner output and storage conditions that maintain the integrity of cold-stored runner tips. Without these improvements it is unlikely that soilless runner tip production will become a widely accepted technique that would replace the field nursery tip production method currently used by commercial strawberry propagators.