Innovation Expands
Tropical Waterlily Season

by Charles B. Thomas
Images by Mark & Martha Prescott
Click to enlarge

At Pondapalooza 2006, I luckily ran into a friend I had not seen for seven years. He astonished everyone he saw there with exciting news for us tropical waterlily and Victoria aficionados.

No matter how many weeks tropical waterlilies bloom before succumbing to the cold, we all would love a few extra autumn weeks to enjoy them. Likewise, we all would love to start them outdoors safely a few extra weeks earlier in the spring. How could anyone accomplish this magic?  

Enter Mark Prescott of Stephentown, NY USA. A long time lover of tropical waterlilies, he operates a wholesale nursery in upstate New York supplying a full line of aquatic plants to garden centers. However, years of consumer resistance to tropical beauties perturbed him. He could not overcome their reluctance. A short blooming season and certain winter loss made tropicals unattractive to them. 

Thermoplanter at Pondapalooza

Three years ago, Mark conceived the idea of warming soil to stimulate tropical waterlilies to produce flowers more weeks per season in outdoor ponds. He not only wanted to create a method for himself, he envisioned a remarkable advantage for his customers’ benefit – one to overcome their disinclination to grow enthralling tropicals.  

Mark had discovered that soil temperature matters more than water or air temperature. He found the trick is to maintain a 70-80 F. (21-27C.) microclimate around a lily’s roots and growth point. He soon designed a unique soil pot equipped with a 70-watt heater. Named Thermoplanter, it allows USDA Zone 4 (temperature conversion chart) water gardeners to start tropical waterlilies outdoors the first week of May instead of mid-June.

Mark Prescott

His innovation encases a thermostatically controlled heater in an inner pot. It uniformly transmits heat to soil in an outer pot insulated to retain warmth. Why not use an aquarium heater? An aquarium heater in an ordinary soil container results in hot spots (burned roots) and a burned out unit.

Field tests in the summer of 2006 indicate that Mark has successfully devised a way to stimulate extra weeks of tropical waterlily blossoms at both ends of the season. Additionally, he finds that his imaginative device works nicely for Victorias.

Late May - Early June

In 2005, Mark’s tropical waterlilies were happily blooming May 7. Imagine! They flowered despite early May frost with air temperature dipping to the mid 20s F. Water temperatures varied from the mid 50s F (around 13 C) to mid 60s F (around 17 C) throughout May. Nevertheless, his tropicals thrived splendidly.

After several autumn frosts or light ice coverage, Mark recommends transferring tropicals with their Thermoplanters to a greenhouse pool or a tank by a sunny window. After mid February, longer days rouse them to begin new growth. In USDA Zones 7 and warmer, Mark says the pots keep tropicals blooming (or at least surviving) outdoors.  

Mark has enlisted other water gardeners to independently test his invention. So far, all of them report remarkable success. Biology Professor Emeritus Dr. Barre Hellquist has years of experience growing Victorias. In the summer of 2006, he tried one in a Thermoplanter in his Massachusetts pond. Viola! By mid August, he realized a breakthrough with his first pre-September Victoria blooms after years of effort. Another Victoria in the same pond without benefit of a Thermoplanter lost the race with 13-inch leaves (33-cm) and no buds by mid-August. 

Earlier, when Barre planted his victorious Victoria, he placed the Thermoplanter inside a ten-gallon (38-liter) pot and filled it with soil. This greatly increased the insulation factor. The plant’s soil was solely in the inner 2.5-gallon (9.5-liter) pot. Only 6-8 inches (15-20 centimeters) of water covered the top, leaving it the only non-insulated area of the system. Mark calls this the Hellquist Method.

Barre’s Victoria flowered and produced 31-inch (79-cm) pads despite low 60s F. (around 16 C.) day (low 50s [around 11 C.] night) water temperatures. The pot maintained an 82 F. (28 C.) temperature, substantially warmer than the surrounding pond water. The Thermoplanter’s warmth prevented cold shock. It spurred the Victoria to flower in spite of adverse cold water and air. Mark estimates Barre’s Victoria used under US$4 worth of electricity -- much less expense than heating the water.

Barre Hellquist's Victoria 'Longwood Hybrid' in Massachusetts in mid-August

Mark anxiously awaits results from England where The Royal Horticultural Society and Professor Craig Baldwin of Sparsholt College are separately conducting tests with four pots each.

With continued winning results, we anticipate that tropical waterlilies will find much greater popularity in many places where mild summer temperatures discourage growing tropicals. Additionally, those who now grow tropicals in temperate climates may enjoy extra weeks of tropical waterlily splendor. Thermoplanters should become generally available in 2007.

This article is not an endorsement of this product. 

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