There are several key factors needed to grow lotus flowers in our USDA zone 4 climate.
Grow this plant in full and hot sun.
Remember this is a river edge grower so sunlight is part of its genetic inheritance. It might help if you remember that the most famous home for this plant is the Egyptian Nile River area. I mention this even though the Lotus is not native to Egypt – it is forever associated with this area in myth and history. Egypt is not noted for its shady garden areas.
A water depth of 4″ to 6″ over the soil line is best right after planting.
However, as the plant grows and leaves shoot up above the water, you can increase water depth by two to three inches.
In containers, and growing on the ledges of ponds, these plants do best in a rich loam and following an old soil recipe; I pack two inches of composted manure on the bottom of the tub before I fill the rest of the tub. That’s all I give them for the season.
You could use a water lily food stake but I prefer the compost.
If you’re growing them in a natural setting, out of containers, then no extra fertilizer is needed. And if you try, you’ll likely only create green or brown water.