The following answer has been selected and edited by New Scientist staffPlants like
Selenicereus flower at night, when temperatures are low and the creatures that pollinate them are about. A white flower opening at night is highly visible, particularly with a full moon to illuminate it, so nocturnal flowering makes sense in evolutionary terms.There is also good evidence to suggest that plants sense the length of the night-time and that these periods trigger flowering. Therefore "interrupting" the night with a bright light such as a full moon could have an effect on flowering in plants. But I know of no scientific studies that have shown this to be the case.An internet search provides very few reports of
Cereus or Selenicereus flowering in response to a full moon. So the questioner's observation is likely to be the result of chance.There are 28 days in a lunar month, and on three of those days the moon will be at its brightest (approximately a full moon). So the plant has roughly a 1-in-9 chance each month of flowering at the time of the full moon. I suspect that if it flowers at another time, the observation is not considered remarkable and so does not get reported.P. Scott, School of Life Sciences, University of Sussex, Brighton, East Sussex, UK
