Plant only flowers after rain, and not from being watered. What plant is it?

Question

My landlord has this plant in his garden. (See pictures at the bottom.) I water it for him several times a week, using water from a closed well.

It doesn't usually rain here. There's maybe one or two periods of rain each year. The rest of the year we have a dry, tropical climate.

No matter how much I water it, this plant never flowers. I've tried copious amounts of water, frequent watering, etc. It doesn't matter.

However, when it rains, like it did this week, it only takes a few days for the plant to give these beautiful flowers. As far as I have seen, this rule never fails. The plant never flowers after being watered with well-water, but always flowers after rains.

What is the name of this plant?

We are in southern India. The plant may be native to this area, it might be native to somewhere else. I'm not sure. But it does fine here, except for the well-water thing.

As for why it only flowers after rain, that is not the purpose of this question, but people are welcome to mention that. I intend to ask it in a sepreate question once I have ascertained the name of the plant.

With a DVD for size comparison:

Answer 1

This plant is Zephyranthes carinata, a bulb with the common name Rain Lily. There are lots of hybrids these days, but the reason they're called rain lilies is because they flower after rain. Some only flower once a year, and that is later in the summer/autumn, when the autumn or summer rains arrive, but some of the newer hybrids flower more often and do respond to watering. However, this one probably only ever intends to flower at certain times, and however much you water inbetween times, it will not force the flowering - that's programmed within the bulb itself.

More info here, though the picture in the link is not of this particular variety

http://www.easytogrowbulbs.com/g-52-rain-lily-zephyranthe-planting-guide.aspx

UPDATED ANSWER

I should have said, these plants require periods of drought, and when they flower in response to rain, its because the humidity is higher, which triggers the flowering response; that doesn't happen with you watering copiously, the humidity may increase a little, but not enough.

https://www.dawn.com/news/883145/nature-talk-rain-lilies

Answer 2

The flowers in the photo are called Rain water lilies , I grow these flowers at my home , I was shocked just like you when I don't know about this in the beggining , then I take a picture of my flowers and googled it , then I find out that this plant is Rain water lilies and yes it grow flowers only through Rain water . As per my opinion you should give water to plant everyday and patiently wait for monsoon season to rain and the flowers will grow , this is the characteristic if this plant it only give flowers through rain water that is why they are called rain water lilies. This my favourite plant because its flowers grow only through Rain water which is somehow magical for me , and I patiently wait for rainy season to see this beautiful rain water lilies bloom.