Hi Wim:
Of Zephyranthes there are over 70 species and depending on their origin they have different cycles and requirements.
Minima is a species of the pampas of my country, Argentina. In the wild it grows in moist pastures, in full sun and receives year round rainfall. Sow now in a standard drained soil and keep growing for as long as you can wihtout forcing dormancy.
The natural cycle is summer dormant, flowers at the beginning of the cycle in autumn, with the tips of the leaves that keep on growing thru autumn, winter and spring.
Flowers are minute, white with carmine red tips. Seeds are largish and rounded. If you remove faded flowers they produce bloom after bloom. Never offsets, only propagates from seed.
Hope this works.