Charles Leach comes to some conclusions about his -

Experiment to Save Energy with
Part 3
plus other suggestions for saving energy
when wintering over tropical waterlilies
(Click here to review Part 1 - Part 2)
by Charles Leach, Ohio USA - Zone 6
Images by Ruth Leach - Click to enlarge


The coldest part of winter has passed and the battle to keep tropical waterlilies awake without having to declare bankruptcy due to energy cost is all but over. This is the final installment in this series. How did we do?

Viviparous lilies in the green house tubs without supplemental heat, above right, did very well overall. The only casualty was a fully developed Nymphaea 'Crystal' that died back without leaving a tuber, but the three baby backup plants in the small heat-mat-warmed tubs on the shelf are doing very well. The other 13 varieties of viviparous lilies in unheated tubs survived and most thrived, blooming throughout the winter; even with room temperatures occasionally dropping as low as 62° F (17 C). The photos below were taken in late winter.

N. 'Paul Stetson'

N. 'Mrs. Martin E. Randig'

N. 'Patricia'

N. 'Madame Ganna Walska'

N. 'Margaret Mary'

As it is well known that viviparous tropical lilies are more cold tolerant than most non-viviparous varieties, it isn't going to come as a surprise that my first recommendation for economical wintering over is to select viviparous varieties or more cold tolerant non-viviparous varieties. One such is 'Star of Zanzibar', left, that thrived and bloomed all winter in our sun room with supplemental lighting.

Non-viviparous varieties in heat-mat-warmed 40 gallon (151 liter) tubs in the green house did fairly well but were not thriving at the dawn of a new year. I decided to extend the mini-heater trial a little by inserting them into a few pots.

< 'Leopardess' - the one on the right with a mini-heater inserted and one on the left without a heater. Obviously the addition of the mini-heater was appreciated.

'Director George T. Moore' >
wasn't doing well before the mini-
heater was inserted into the pot. 

My conclusion is that the heat mats under the 40 gallon (151 liter) tubs did not warm the water quite enough to make most non-viviparous tropicals happy in a room where air temperatures dropped into the low 60's F (mid-teens C) and that the mini-heaters provided the boost required.

Results with non-viviparous lilies in the sun room were mixed, probably because of limited light in what has been a very dark winter. The photo at the right shows a 'Hickory Bend Ruth' in the sun room last winter with no supplemental heat. It bloomed like crazy and had lot of beautiful leaves until early spring when it nearly went dormant. 'Hickory Bend Ruths' in the same location this winter hung on and the one with a mini-heater did better, though neither thrived nor bloomed.

As reported previously, recognizing that most varieties were not getting enough light, I resorted to using clamp-on grow lights to keep the varieties that were still kicking in late December from joining 'Red Flare', 'Mary Francis' and a couple others in going dormant. It should be noted that 'Mary Francis', like 'Hickory Bend Ruth', was very happy in the same location, without supplemental heat last winter which was sunnier. 

Results of the mini-heater trials in the basement tubs were disappointing. Although most plants in the approximately 7 cup (1.7 liter) size pots did well with only mini-heaters in their pots in the basement (where temperature often drops to 60° F [16 C]), 'Albert Greenberg', 'Red Flare' and 'Trudy Slocum' in 5 quart pails died or barely survived. "Ruth", 'Leopardess' and 'Midnight' in 5 quart (5.5 liter) pails did a little better but didn't bloom. I strongly suspect that the difference had as much to do with various varieties' tolerance of artificial illumination as with the failure of the mini-heaters to hold soil temperature high enough.

What have we learned about using mini-heaters to conserve energy when wintering over tropical waterlilies?

1. Amount of heat generated seems to vary considerably from heater to heater, especially with the Junior Aquarium Heaters from WalMart. A thermometer probe placed in contact with some heaters registered only about 90° F (32 C), while contact with other heaters registered up to 120° F (49 C). Needless to say I moved the high-reading heaters a little farther away from the crowns. A few heaters that generated very little heat were returned.

2. They do not perform miracles. Little 7.5 watt mini-heaters will warm the soil near them a little under 10° F (5 C). They do a pretty good job of warming whole pots in the 5 cup size range, even in the basement where temperature dropped into the low 60° F (16 C) range but were generally unable to keep plants in 5 quart pails happy in such low temperatures. Two or three heaters may have worked in the larger pots but it would be a case of diminishing returns. If there are six pails in a tub, with three 7.5 watt heaters in each, why not just use one 150 watt heater, with a thermostat that would shut it off when water temperature was high enough? The mini-heaters seem relatively effective in 5 quart pails in the sun room where we try to keep room temperature above 70° F (21 C).

3. They can be a small part of an energy conservation program, not the whole program. Mini-heaters are sort of like an inside sweater in the winter. They can prevent chilling in rooms in which the temperature is reduced to 65° F (18C) but not much more.  

Rethinking and Applying Lessons Learned

The mini-heater experiment was part of an overall attempt to keep skyrocketing costs of wintering over tropicals in check and, based on this year's results they will be part of our ongoing effort, but only a small part. In order to come up with a plan to do a better job of containing costs next year it is necessary to look at the bigger picture, starting with examining why we have attempted to keep tropical lilies growing through winter.

Why have we insisted on keeping tropical lilies growing through winter? The primary reason is that my wife Ruth and I really enjoy having beautiful waterlily flowers all winter long. We also have had a lack of confidence that stored tubers would survive winter and some varieties have not formed storage tubers for us. Thanks to resources at, we probably have a handle on why so many of our lilies fail to form tubers, but I'll get into that later, and given fairly good results with tubers stored over last winter we are not as worried about storing them. Of special concern previously, because the lily existed nowhere else, has been the possibility of losing stored 'Hickory Bend Ruth' tubers. Tubers of this variety seem to store exceptionally well and a friend is now growing this treasure so there is a source of replacements.

Why bother if they don't bloom? Last winter only one non-viviparous lily ('Star of Zanzibar') bloomed consistently and it had supplemental lighting. Looking at the situation with cold logic, we have been going about keeping lilies growing through winter for our enjoyment all wrong. We have been keeping non-viviparous lilies that haven't been blooming in the sun room. There they are far more visible and we pass them many times a day. We've kept our viviparous varieties in the attached green house where they are out of sight. Energy costs aside, this is dumb because we have the non-viviparous varieties that need more light in the sun room where they get only filtered light, while keeping the viviparous varieties in the green house where they get more sunlight. If we switched the types, the fact that we are trying to cut energy costs is impractical, because keeping the green house temperature high enough for non-viviparous tropical waterlilies would make our electric meter spin like a top.

Rethinking our situation. It has been suggested that we would be better off letting our tropicals go dormant in the winter. Given overall success in storing tubers this past winter, probably due to better temperature control, I feel far more comfortable doing so. Kit Knotts also addressed failure of some of our lilies to form tubers by pointing out something that should have been obvious to me. Keeping lilies growing through a southern Ohio winter is in effect the same as growing them in Florida..

That being the case "Tubering Tropical Waterlilies in Warm Climates", which I had previously ignored, is applicable, and it seems I have been keeping my tropicals too happy for them to bother forming tubers. It's sort of like the story about a boy who didn't speak until he was 11 years old. One morning he surprised everyone by complaining that the toast was burned. "Why haven't you ever talked before?" his mother asked. "Up to now everything has been OK," the boy said. Guess it is the same with tropical waterlilies. As long as everything is OK they don't speak up by forming tubers.

Another article that is applicable, but I ignored previously because I thought it didn't apply to our zone, is "Repotting Overgrown Tropical Waterlilies", which explains why some of the lilies we bring in and repot for winter die. From now on we will "turn" or "chop and drop" old tubers so that they don't affect healthy growth above them.

Our New Plan

I wasn't planning a major overhaul of our wintering over program but it looks like that is what we are going to do. To reduce energy cost as much as possible we intend to implement the following, roughly step by step, plan:

Step 1: We are going to order quite a few new tropical waterlily varieties because, by letting most to go dormant, we will have enough room to winter over more varieties.

Step 2: We will promote formation of storage tubers / Kit Knotts "Tubering Tropical Waterlilies In Warm Climates" article.

Step 3: Tubers of as many varieties as possible will be stored in damp peat moss, possibly in a mini-refrigerator to maintain cool temperatures over a longer period.

Step 4: We will keep all, primarily viviparous, varieties that we want to keep growing through winter in the sun room and not have electric heaters running in the green house until we bring tubers out of storage to float and sprout on the heated shelf in the green house in early spring.

Step 5: We will postpone potting sprouts in small pots and repotting into larger pots for placement in green house tubs and heated basement tubs until April or May.

Step 6: Varieties that don't make it through the winter as outlined above will no longer be grown.

Hope our little experiment will help a few people lower energy costs a bit. 


Experiment to Save Energy with Mini-Heaters
Part 1 - Part 2

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