Here is a photo of lilies in our back yard.
I had always called them Rain Lilies because they pop up after rainstorms, but an on-line check tells me that they are Red Spider Lilies (Lycoris Radiata).
When I said pop up, I meant that literally. They go from invisible to bundles of blooms on a 16 inch stem in less than a day.
I don't know where they came from - we never bought any, so they probably hitchhiked in on something we did buy. I don't do anything to encourage them, in fact the brown in the fence line just behind them is the result of spraying weed killer a few weeks ago.
The particular blooms seen here were generated by what rain we got from Tropical Storm Beta.