Dear Mary Sue In the old days, back in the 40's, we used to save rain water in cisterns, barrels etc., and used this on our plants. I have not seen an analysis on the qualities of our drinking water compared with rain water, but given it is treated, chemicals added, I think it possible germination and/or growth inhibiting chemicals are to be found in our drinking water. Your observations regarding growth after rains, even when plants have been watered, could perhaps be simply due to this. Cheers, John E. Bryan