After a quick google scholar search, the abstracts that I have read suggest that temperatures above (not below) 17C during active growth (not dormancy) could induce flower bud abortion in some species. Optimal flowering occurred following vegetative growth at temperatures BELOW 17C. One cannot know from only reading the abstracts whether air or bulb temperature was monitored or controlled in the research mentioned above. In the real world, the possibility of the interior bulb temperature matching the ambient air temperature is nearly nonexistent in most circumstances. However, if you are growing your Nerine sarniensis in black plastic pots, like I am, you might improve your flowering by preventing the low winter sun from blasting the side of the pots during those sunny winter days (during active vegetative growth). Nathan Lange