Planting Hardy Water lilies
Place the tuber at a 45° angle with the non-growing end against the side of the pot and the crown (where the leaves come out) towards the middle of the pot. Do not plant too deeply--the cut end should be deep enough to keep the buoyant rhizome from popping out of the soil, but the growing end should be at or only slightly below soil level. Add either several tablets of fertilizer or a 1 yr fertilizer spike. Lilies are heavy feeders and should be fertilized monthly (if using tablets) after planting throughout the growing season. Be careful that the fertilizer is not touching the new roots as this may burn them. Press the soil around the roots, being careful to barely cover the crown of the plant. Covering the crown any deeper may kill your water lily. It is better to plant lilies too high than to plant them too deep. Hardy lilies are placed at the bottom of the pond. Large to medium varieties should be placed at a water depth of 18" to 30". Small varieties should be placed at a water depth of 12" to 24". Dwarf varieties should be placed at a water depth of 6" to 12". When placing lilies in the pond, position them away from waterfalls and fountains as they prefer still water.
Once they reach a mature size, large waterlily cultivars may be moved into deeper water. With a large pot and adequate fertilizer, a large cultivar will be happy in water up to 5 feet deep or even a little deeper, but it takes time to grow a plant to this point.
For specific planting depths and type of container to use read the plant information at the bottom of the item description for the plant you are planting.