Bonjour Aad, It depends on the species, but generally I have succeeded best with shortening the dormant period, if you can get the bulbs as soon as they have been lifted. With a January planting the bulbs may get started and will go dormant again in June. Kind greetings Lauw de Jager, South of France http://www.bulbargence.com/ -----Original Message----- How long will it take to convert a bulb from southern to northern hemisphere and what is the best approach to do it. For instance is it beter to lengthen the dormant period or the active growth period