Experiments on the retardation of Dutch Irises

The normal market of Dutch bulbs lies in the Northern Hemisphere since the successful growing of these bulbs is only possible in those countries where the temperature during winter is not too high. In tropical regions it is not possible to grow normal flowers, unless a low temperature can be provided after planting by artificial means; e.g. by planting the bulbs in pots or boxes and keeping them in cold storage for some months at a temperature in the region of 10°C. (Beijer 1948) Formerly this same need for a low temperature following planting seemed to prevent the exportation to the Southern Hemisphere, for when sent at the normal time, in September or October, on their arrival in South Africa, South America or Australia the bulbs had to withstand the very high summer temperature prevailing. Planting during this summer period nearly always resulted in failure to flower, and was often followed by total loss of the bulbs.