The question of promoting tuber production of tropical waterlilies has come up many times in the past and the answer has been published in several articles and books. Unfortunately, these publications often have had limited distribution and therefore seldom quoted. Consequently, I will try to list as many of these sources of which I have personal knowledge and, where practical, copy out a passage from them.

To start with, one could peruse the several pertinent articles found in the Water Garden Journal. Below are listed the Volume (Number): Page. Title and Author of these Journal articles:

1(3):18. Tuber Production of Night-Blooming Waterlilies, by Kirk Strawn

2(4):21. The Culture and Storage of Tropical Day-blooming Waterlily Tubers, by Kirk Strawn

15(4):16. Production Procedures for Tropical Waterlily Tubers, by Evan Williams

16(1):19. Propagation of Tender Waterlilies, by Pete Bisset

17(2):9. Nursery Production of Tropical (Water) Lilies, by Brad McLane

Although many books have been written on waterlilies, few have addressed methods of directly producing resting (hard) tubers in tropical waterlilies. Even Charles Otto Masters in his 1974 "Encyclopedia of the Water-lily" devotes only one sentence to it. This can be easily missed in this 512 page book.

I find only three books (out of over 150 published since 1850) that treat the subject adequately. They are:

William Tricker. The Water Garden, 1897

Peter Bisset. The Book of Water Gardening, 1909, 1924, 1929

Robert Sawyer & E, Perkins. Water Gardens and Goldfish, 1928, 1934

For those who may find it difficult to procure these books, I quote from Wm. Tricker (p. 47):

"The most simple and easy method of holding stock plants is to keep one or two of a kind in 4 or 5 inch pots during the summer; they will probably exhaust the plant food in these small pots before the season is over, and may give but little bloom, but show a tendency to go to rest early, the leaves take on autumn hues and tubers are formed. At the proper time these plants should be taken out of the water, and the pots, with their contents, placed under the bench in the greenhouse or other suitable or convenient place. If left too long in the water and the weather is hot, the tubers may restart growth. If taken out of the water too soon, the tubers may not be sufficiently ripe to keep until they are wanted to start in the following spring."

Peter Bisset clarifies the time when the plants should be taken out of the water in his 1929 edition (p. 135):

"When the plant tubers have ripened, which will be shown by the leaves becoming yellow, brown and red, the pots should be taken from the water and laid on their side in a moist place under the greenhouse bench, where they will not dry out too rapidly, and where is maintained a temperature of from 50 to 60 degrees Fahrenheit. Here they should remain, protected from mice and rats, until spring."

Robert Sawyer adds to this in his second (1934) edition (p. 128):

"Nymphaea caerulea and N. zanzibariensis will often refuse to form bulbs in five inch pots because they overgrow. Try them in two inch pots and they will nearly always form good bulbs -- small ones but sound and vigorous."

In his Encyclopedia, Charles Otto Masters summarizes all this up in one sentence (p 84):

"Occasionally tropicals in outdoor pools can be induced to produce tubers by placing them in pots or containers which are really too small but which through root binding and exhaustion of nutrients, tend toward tuber production."

Since many of us do not have a greenhouse bench under which to store the potted tubers until spring, several alternate methods have been used in recent years. Two of these are:

1) Wash the tubers and store them covered with slightly moist sand or sawdust in closed jars.

2) Put the cleaned tubers with a little water in sealed plastic bags and store in a cool rodent-proof place.