12月促成開花に適したボタンの品種選抜

Cultivars of tree peony (Paeonia sulfruticosa Andr.) suitable for December flowering were searched. Two-year old grafted plants were lifted from the field, chilled at 3℃ for 47 days from late September, planted in the pots and cultured in the heated glasshouse. Pink cultivars, 'Hanakisoi' and 'Yatsukajishi' successfully flowered in late December. 'Yatsukajishi' needed prechilling treatment (15℃ for 11 days) for normal leaf extension. Red cultivars, 'Higurashi' and 'Nichigetsunishiki' also successfully flowered although days from planting to flowering in 'Higurashi' were relatively long. Purple cultivars, 'Shimadaijin' and 'Hanadaijin' were also suitable cultivars for December flowering. White cultivars were very difficult since flower blasting occurred at high rate. It was demonstrated in the test of 'Hanakisoi' that the bud size before chilling was closely related with occurrence of blasting. Thus, plants with large buds (10 mm or so in diameter) should be used for commercially successful flowering (80 % or above) in December.