Primlarp Wasuwat Chukiatman
Photo by Byoung Sup Ghill

We know that tropical day-blooming waterlilies cross-pollinate and set seed freely. Every day we can find new hybrids in our ponds. Some look the same but we cannot be sure that they are the same or different unless we find the key characteristics to identify them. Growers need to look carefully at their hybrids or they might sell the wrong one to the customer.

As an example I show you two varieties of tropical day-blooming waterlilies that really look alike when we first see them. They are Nymphaea 'Thongsook' and N. 'Lueang Thong'.

Look at these two flowers. Can you tell the difference between them? They appear similar in the flower shape, number of petals and the colour. In fact, the flower on the left is N. 'Thongsook' and on the right is N. 'Lueang Thong'. These two cultivars were produced by Dr. Slearmlarp Wasuwat who selected them from open-pollinated hybrids of N. 'Trail Blazer' in 1988 and introduced them in 1992.

I cannot tell the difference from the flowers. These two cultivars are medium sized waterlilies which need water depth of 0.30-0.60 m (12-24") and their diameter is 0.45 m (18") and larger. They need at least four hours a day of sunlight. I must find the key to tell the different between the two of them with my eyes. The clues follow:

It's much easier to tell the difference from the leaves. N. 'Thongsook's' sinus is partially open but N. 'Lueang Thong's' is fully open. Another outstanding characteristic is the colour of the back side of the leaf. N. 'Thongsook's' background colour is almost entirely purple while N. 'Lueang Thong's' is almost entirely green with some purple near the sinus.

If you ask me how to tell the difference between N. 'Thongsook' and N.'Lueang Thong' simply, of course I will tell you to look closely at the leaves.