In order to establish the computer control system in the early forcing of iris, the effect of temperature in the initial stage on the growth and flowering was studied for 3 years.
1. The Bulbs ofiris 'Wedgwood' were planted on September 26,1976 and kept for 20 days at three different temperatures ; high, middle and low. From that time on, they were transplanted to a computer-controlled green house and received the same growing conditions until harvest time.
2. Though the number of days required for flowering after planting became smaller in proportion to the increase of temperature in the initial stage, the cut flowers of high temperature section were inferior to those of other two sections both in yield and quality. The same tendency was observed in the early forcings of iris at our experi mental farm in the past two years.
3. As 22℃ was assumed to be the upper limit of temperature favorable for the growth of iris, the accumulated excess room temperature over 22℃ was calculated in the three temperature sections for each 5 days of the initial stage. As the results, the value in the high temperature section was about 200% and the value in the low temperature section was 28% of that in the middle temperature section.
4. In 1975 when the temperature in the initial stage was relatively high, the flowering rate was extremely lower than those in 1974 and 1976.
5. From these results, it can be said that the planting time of iris bulbs in early forcing should be determined on the basis of long-range weather forecast since it is still difficult to keep the temperatue in the initial stage adequate for the growth of iris without powerful air-cooling devices.