Flowers will only last one day, and if left un-pollinated, will fall off. The plants are self-fertile, and pollination requires the transfer of the pollen from the anther to the stigma, which involves using a small splinter of wood or a grass stem to carefully lift the rostellum (i.e. flap) out of the way and press the overhanging anther against the stigma. You need to do this soon after the flower opens. Remember that the flower only lasts one day....never to open again - so you need to be observant.

The vine should be able to produce vanilla pods after 2 or 3 years of good growth.