Lotus are generally grown from rhizomes planted in late May or early June. If a lotus is to be grown in a pond or pool, it should be planted in shallow water (15 to 50 cm below the surface), directly in the bottom or in a container 30 cm tall and 50 cm across. The water temperature must be at least 18°C during the growing season. The soil must be quite rich, i.e. one part loam, one part leaf mold, compost or well-aged manure and one part clay soil. Slow-dissolving fertilizer, such as bone meal, may also be added.
A lotus may also be grown in a pot, which should be 60 cm in both height and diameter. The advantage of this method is that the water will warm up faster and the plant flower earlier. Place a 25 to 30 cm thick layer of the appropriate soil mixture in the bottom of the pot. Plant the rhizome horizontally, on a slight angle, and cover all but the last 2.5 cm of the growing tip with soil.
Then cover the growing tip with 10 cm of water. Gradually raise the level of the water until it is about 20 to 25 cm deep, as the heat of the sun will encourage the foliage to emerge quickly. Blooms will appear earlier if the rhizome is placed in a container in a hothouse heated to 18 to 22°C. The lotus prefers a very sunny location. Cooler temperatures may cause the plant to go into dormancy, and it may be difficult to coax it to rebloom. For better growth and flowering, slow-release fertilizer tablets may be used once a month, and the first flowers should be removed as soon as they fade.
The lotus is normally propagated by rhizome division, with two or three eyes being kept on each section. It can also be propagated from seed. Lotus seeds have a highly effective dormancy mechanism and require a number of specific steps to encourage them to germinate. The surface of the seeds must first be scarified to break the outer coating. Then they should be placed in a container, a drinking glass for instance, filled with a few centimeters of water, which must be changed daily. Each plant should be pricked out once two leaves emerge, along with rootlets. Plants started from seed in March may flower the first year, in August and September, while rhizomes planted in containers will flower in July.
In our climate, it is best to lift the rhizomes in the fall. They should be stored in their original soil, covered with 5 to 20 cm of water and kept cool (5° to 10°C), safe from any risk of freezing. Plants grown in the bottom of pools or ponds should be protected with sheets of plywood and polystyrene to protect the rhizomes from freezing. Containers may also be moved to a deeper part of the pond where the water does not freeze.
Plants should be divided every three or four years.