Tropical water lily tubers can be stored dormant. Tubers may be sprouted to produce plantlet(s). If these plantlets are grown on, they will produce adult, flowering plants. This guide applies to tropical nymphaea species, cultivars and hybrids in the brachyseras subgenus.
This is the author’s personal method of growing tropical water lilies from tubers. Parts of this article rely on content from “Hybridizing Waterlilies: State of the Art” and https://www.watergardenersinternational.org/journal/1-2/rich/page1.html
Timing is entirely dependant on your climate. I personally start my tropical water lily tubers in early April and aim at planting the adolecent plants out in the outdoor pond in early to mid June. For other areas, find out when the water temperature reaches 20 degrees Celsius and count back 2 months.
If you have tubers that do not show growth yet, these can be forced. To force a tuber, place the tuber in hot water (29-32 degrees Celsius) until growth emerges. It may take less than a week to months before growth emerges.
Your tuber might already show growth at one or multiple growing tips. Already sprouted tubers can be encouraged into further growth by placing the tuber in warm water, 22-26 degrees Celsius. No soil is required. As soon as new growth emerges, adequate lighting is of importance. Keep the tuber at a depth of 10-15cm below the water line.
Your tuber will now continue pushing out new (submerged) leaves that increase in size. These leaves may look deformed. Depending on the parentage of the tropical lily, the plantlet may keep producing submerged leaves for one week to several weeks until the first floating leaf appears.
Once your plantlet has a bundle of roots a couple of cm long (and possibly a few floating leaves), it is ready to be separated from the tuber.
Find the part where the plantlet is attached to the tuber and cut the plantlet away from the tuber. Take care to preserve the roots, crown and leaves of the plantlet. In some cases, a gentle twist and pull is enough to separate the plantlet.
Find a small plastic pot, 9 to 15cm. The pot may have holes in the bottom. Pots with no holes leak less soil and nutrients and can help keep the water clear in nursery ponds. Fill the pot with a layer of heavy soil. Mix in one quarter to half a fertilizer tablet. Fill the rest of the pot with soil. Make a hole for the plantlet’s roots. Insert the plantlet so that the crown of the plantlet is flush with the soil level. The crown of the plantlet is the point where new leaves emerge. Fill back the soil around the plantlet’s roots.
Place the potted plantlet in a brightly lit water vessel. Allow around 10-15 cm of water over the crown of the plantlet. Maintain the water temperature at 22-26 degrees Celsius. In areas with short day lengths, artificial lighting may prove to be of great advantage. Your water lily should keep sending out new floating leaves that increase in size. Once the plant has filled the soil with roots, it is time to pot the plant on to a larger pot to allow further development.
Once the plant has again filled the pot with roots, find a pot that is wider than it is deep. 15 litres of soil is a minimum. The larger the pot, the larger your lily will grow. Put in a layer of heavy soil. Grind a fertilizer tablet and mix it into the soil. Plant the water lily into the soil with the crown of the plant at the same level as it was before.
If your water temperature has reached 20 degrees Celsius then you may now plant the lily out into its final position. A depth of 20-40cm below the water line is optimal. If the floating leaves of your lily do not reach the surface immediately, use bricks to lift the pot until the leaves are within 10cm from the water line. Once the leaves have reached the water line, take away a brick and keep repeating this process until the lily is at your desired depth.
From now on, follow the instructions on the fertilizer packet on dose and frequency. Water lilies are heavy feeders so fertilizing is essential for numerous blooms and healthy growth.