To facilitate the production of white asparagus (Asparagus officinalis L.) spears in winter, we studied spear blanching in rootstock planting forcing culture. A strong correlation was observed between the fresh weight of one-year-old rootstocks and their yields. Light conditions during the harvesting time had little influence on the yield, but, they influenced anthocyanin pigmentation in the spear. When asparagus spears were harvested under darkness maintained by an opaque film covering, anthocyanin pigments in the spears disappeared. There were differences between cultivar yields; these were caused by the differences in the extent of chilling exposure, which is necessary for each cultivar to break the dormancy of its rootstock. These results suggested that white asparagus spears can be produced with no anthocyanin pigment in forcing culture by using oneyear-old rootstocks of cultivars with a low level of dormancy ('UC-157 F 1 ', 'GrandeF 1 '), if spears are harvested under dark conditions maintained by opaque film covering.Key Words：anthocyanin, dormancy, light condition, opaque film covering

This study produced white asparagus (Asparagus officinalis L.) spears by covering plants with a shading film during semiforcing spring harvest cultivations of asparagus. White asparagus spears with no anthocyanin pigment were produced in plastic houses, when a 2.0 m-highwalk-in tunnel covered with a shading film was set up in the houses before the spears sprouted. The number of marketable white spears was smaller than that of marketable green spears. However, the weight of white spears was greater than that of green spears. Consequently, there was no difference between white and green asparagus production with regard to marketable yield. The characteristics of white asparagus spears produced in plastic houses with a shading film covering differed from those of green spears. Their tips were tighter and mid-section diameters were greater. Further, white asparagus spears that had been boiled for 10 minutes tended to be tougher than similarly treated green spears. Key Words：characteristics

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The combination effect of sowing and transplanting time on harvest time, yield, and external bulb quality was investigated to achieve earlier shipment of onions in northeastern Hokkaido, Japan. A total of five cultivars with different levels of photoperiodic responses for bulb formation were used in both the 1996/97 and 1997/98 trials. The seeds were sown on a monthly basis in a soil bed in an unheated plastic greenhouse from December to March, and the seedlings were transplanted outdoors from late April to mid-May. The daily minimum soil temperature was kept at almost 0°C, even when the air temperature in the plastic tunnel inside the greenhouse fell to −14.4°C in midwinter. Seedling emergence took approximately 20 and 35 days in the 1996/97 and 1997/98 trials, respectively, when the seeds were sown in December and January. However, these seedlings grew slowly, and the leaf length, fresh leaf number, and leaf sheath diameter of the seedlings at transplanting time were all greater when the onion seeds were sown earlier. In addition, the bulb ripening time advanced with earlier transplanting. The cultivars, 'Kitawase No. 3' and 'Kitahayate', with an intermediate photoperiodic response, were harvested in early August if they were sown in December and January and transplanted from late April to early May. Moreover, with this combination of sowing and transplanting time, these cultivars produced an acceptable yield and bulb appearance in terms of marketable quality. The cultivar, 'Sonic', a typical short-day cultivar, had the earliest harvest time. However, the yield was very low due to the short period of leaf growth. On the other hand, for the cultivars 'Okhotsk No. 1' and 'Kitamomiji 86', which belong to a long-day photoperiodic response group, although the yields tended to increase under early sowing or early transplanting, they were not harvested by early August. On the basis of these observations, a new cropping type for early sowing and early transplanting will be adopted in northeastern Hokkaido by using the 'Kitawase No. 3' and 'Kitahayate' cultivars for early shipment in the domestic fresh onion market.

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