What you need to do is take the bulb out when all the foliage has died back and store it in a warm dry dark place I usually put all my crinum bulbs into paper bags they must be kept dry.

I got my Crinum from my brother, as next door neighbour wanted it out of the way for her boys to play football in her yard. It was only a little tiny offset but it is now a huge plant community in a large pot outside. I have one in the garden that survived our severe winter this year. I know it will get to be huge. If you want to stay in control, then take it up and store as suggested. The original crinum is now in several gardens as my brother gardens for several friends.