This study was undertaken to clarify the growth and development of flower budin herbaceous peony and the effect of chilling period on the flowering of forcedherbaceous peony.
The leaf number increased from June 20(at the beginning of investigation) toSeptember 28, but no differentiation of bracts was found. Sepals were observed atthe first 10 days of October, the differentiation of petals from the middle 10 days ofOctober, stamens from the middle 10 days of November and pistils from the last 10days of November.
The longer the chilling period, the longer the length of flower bud was. Norelationship was found between chilling period and the diameter of flower bud. Noincrease in petal number was recognized during chilling.
The earlier the planting date, the earlier the sprouting and flowering were. Thenumber of days from planting to flowering was shortened with increasing chillingperiod. The cumulative temperature from sprouting to flowering was almostconstant regardless of chilling period. The flowering percentage in plot 1 (chillingat 4℃ for 30 days) was the highest (67%), but it did not reach 80% (the base limit forcommercial production). The cut-flower quality was good in all plots and was notaffected by chilling period.