Water lily is a common name for a genus of aquatics called nymphea. The water lily's scientific family is Nympheaceae of the order Nymphaeales. About 70 species of lilies exist and are divided into tropical water lilies, hardy water lilies and night-blooming water lilies. The night bloomer is a tropical lily, not hardy, and will die if it it freezes.

Most people love hardy water lilies and everyone can have them. I have seen them growing in Nymph Lake in Rocky Mountain National Park at 12,000 feet above sea level.

Growing tropical water lilies
Tropical water lilies are grown in the tropical climates of our world. They are beautiful, with bloom stalks shooting in the air almost a foot with an intensely colored flower waving at the end at the slightest breeze. Most are aromatic and make the garden smell of tropical paradises that most of us never visit except in our back yards.

All water lilies need a minimum of 6 hours of sun daily. Put the pots at least 18" below the surface of the water.

Fertilizing tropical water lilies
Tropical water lily leaves reach the top of the pond in May after being dormant during the colder, shorter days of winter. That is when we begin fertilizing. Water lilies are heavy feeders and will love food at least once a month. I have been known to feed every two weeks. They like aquatic plant tabs that are simply pushed into the soil with your thumb, one tab per gallon of pot. If you don't have aquatic plant tabs, use tree spikes cut into four pieces. Tomato spikes also work well. The only fertilizer I have not tried is a time-released one like Osmocote because that is activated by water, so I don't know if it would be released too rapidly to do much good. If you have many water lilies, you may want to stagger the feeding schedule because any fertilizer feeds all water plants, algae included, so you may inadvertently turn your water green with too much fertilizer.