Water Gardening
in a Basement Greenhouse

by Stuart Culp - Click images to enlarge

Central New York State is not what a tropical plant grower would consider to be a paradise, to say the least. Short summers and a fairly high latitude limit the growing season to July and August, and even then a break in the weather can require some night-time protection.

Water lily nurseries will ship stock in early June, and successful plantings result, but the pond water is barely 65°F at that time (maybe even cooler at the bottom if some circulation is not provided) and for the plant to become acclimatized and produce a month or two of bloom that summer is a difficult task. It has been my experience that tropical water lily growth is minimal with root temperatures much below 70°F (remember, that is at the bottom of the pond where the water is at its coolest). Plants accustomed to 75°F will go into shock if lowered to 65°F and will take weeks to recover. It is not usually until the first of July that pond water reaches a reliable 70°F when growth can begin in earnest. Also killing frosts can occur by the first of September, although they have not done so in recent years.

The difficulty with keeping tropical lilies over the winter usually prompts the recommendation that they be treated as annuals, starting over the fresh stock each spring. But this is just the opposite of what the above experiences would suggest. It takes a full season just to get a plant established. Nothing beats the blooms from a mature plant several seasons old. It would be great if the outdoor season could be started with adult, blooming plants on the first of July. What a bonus it would be if the season could be extended all the year-round! The cost of heating a greenhouse or small conservatory to tropical conditions is enormous in these latitudes, so what can be done? I can hear some of you saying, "move south!" But what I have evolved gives me a compromise on the best of both worlds.
An indoor greenhouse in the basement allows me to putter in tropical splendor, while outside, a snowstorm prepares the mountains for a weekend of skiing. After several years of growing hardy only hardy lilies, I purchased a Nymphaea 'Mrs. Martin E. Randig'. At the end of summer, it was just getting started. I did not have the heart to throw such a beautiful plant away, so to the basement it went and into a half whiskey barrel lined with plastic. It was lit with a 100w reflectored light bulb connected to a timer to give 12 or so hours of daylight.

Grow room crowded with
tropical plants.
The need for an aquarium heater was soon apparent. Under these pathetic conditions many of the leaves were unable to unfurl, and the tub was far too small to allow more than a few leaves to float on the surface. But it lived! By the end of the next summer, it and several viviparous offshoots were healthy and blooming. I was hooked! But the whiskey barrel approach definitely had to go.  

The next winter, the whiskey barrel gave way to a child's wading pool 6' across and about 20" deep. Substituting for the 100w bulb were four two-tube 4' reflectored fluorescent lamp fixtures. The aquarium heaters grew to three, barely able to keep up with the load. I began to devour books on indoor gardening, and my telephone bill grew. Experimentation with various types of fluorescent bulbs produced little change in the way the plants grew. Even at a distance of 6" the light output of the fixtures was too low for such subtle differences to matter to the lumen-hungry, high energy lilies. But the procedure was successful, and I was now convinced that what I was doing could be reliably repeated.

However, two changes had to be made. The 65°F basement temperature was not compatible with what I was doing. Some form of insulation had to be added, and the evaporation of water was enormous. Both of these issues were partly solved through the addition of a plastic shroud draped over the whole affair. This gave the benefit of additional humidity, but took away from whatever visual enjoyment I may have had at the time. The following season brought about a larger, room-like plastic drape and the addition of a small agricultural 1000w water heater operated from a timer to raise the water temperature to the mid seventies F. But by now a further problem had arisen.  
Success was going to my head and Nymphaea 'Mrs. Emily Grant Hutchings' was added to my collection. Wonder of wonders, it bloomed a couple of times over the winter, but its blossoms pushed up into the fluorescent fixtures and were distorted and bent. I was starting to get picky. Not only that, but it fared much better in the low light conditions, and had to be continually cut back to keep it from completely choking back the less vigorous 'Mrs. Martin E. Randig'.  

N. 'Emily Grant Hutchings'

Other complications arose. Water hyacinths were added, and these also had to be overwintered. Plastic buckets with individual incandescent light bulbs worked, but the drape room was starting to look like something out of a Rube Goldberg cartoon. Anyone entering the room was threatened by electrocution!

By this time, my wife and I were taking occasional trips to the Caribbean. Seeds from tropical plants somehow found their way into our luggage. These soon sprouted and grew prolifically, they demanded a warm humid environment. You guessed it - into the drape room! Also, a few of our goldfish friends were now coming in from the ice and spending the winter in the basement. I had now advanced to Preferred Customer Status with the local power company, and was expecting a Christmas card from them. Several kilowatts of power were being poorly applied. The costs of a greenhouse or conservatory addition to the house were again explored. The location of our house dictates that the only location for good winter sun is in the front. A Burger King addition just wouldn't work out. So, it was back to the basement. I'm sure the neighbors appreciated my decision. By now I had a pretty good idea of what I wanted in the long run:

1. Space to move around in and to allow for expansion.
2. Two lagoons to allow for species separation and general experimentation.
3. A humidity barrier, both for plant health and minimizing evaporation.
4. Insulation, to remove the need for a heater.
5. Sufficient light at the growing surface, projected from four or more feet away.

Using inexpensive 1"x2" furring strips as studding, an 8'x14' room was constructed in the basement. A horizontal strip served as a base for the studs and was held to the floor using concrete anchors. The studs extended to the basement ceiling. A similarly framed door served as an entrance. Four mil clear plastic sheeting was stapled overall to provide a vapor barrier. Over this was placed a layer of ¾" "Foamular" extruded polystyrene insulation. Two 6'x4'xl8" deep lagoons were constructed, each holding 230 gallons. To cut costs and allow a custom design, these were constructed by using plywood, epoxy paint and silicone sealants, and were an interesting project by themselves. Windows in the sides of the lagoons allowed the viewing of fish. Potted plants were arranged around the edges on small shelves.
A metal halide lamp fixture was mounted over the center of each lagoon. Around the periphery of the room were hung, on adjustable chains, 4' two-tube fluorescent fixtures to provide light above the edges of the circle of light provided by the metal halide lamps. Item five was the most difficult to decide upon. The literature seemed to say that 1000 foot-candles (fc) or more would suffice - the more the better. But I was sure that hardware cost and kilowatts would be the limiting factor.  

Undershooting the mark was my biggest concern. Both General Electric and Sylvania were very helpful, and sent rafts of literature, but the horticultural applications were at the opposite ends of the spectrum - African violets at one end and commercial greenhouse supplementary light at the other. One of the most practical sources of information was the literature produced by indoor marijuana growers! 

Incandescent, fluorescent and mercury vapor lamps were rejected as having too low an output, although fluorescent light and a few incandescent spots were ultimately used as spot fillers. High and low pressure sodium lamps give poor color rendition. Metal halide is the modern lamp of choice; 400w and 1000w bulbs are the best choice for this application. One would think that a 1000w setup would cost less than two 400w units, but such is not the case. Using 400w fixtures allows better distribution of light and more versatility, but less overall intensity. I use Cooper Industries "Lumark", model number MHSS-M-400-MT-U fixtures with MH400 C/U bulbs. These can be purchased from discount electrical supply houses for about $200 each, including the bulb.

Mounting the lamps at the proper height proved the greatest challenge. Too high results in nice coverage, but too low a light level. At a height of 3' above the water, I get "adequate" intensity over an area about 4'x6'. By "adequate", I don't mean 1000fc. It is closer to 500fc. To achieve a level of 1000fc, the height above water would be about 2' using my present set-up, but then the lighted area would be less. It is possible to adjust the position of the reflector relative to the bulb to change the spot size somewhat, and adjustment holes are provided for this.

To illuminate an area described from a height of 2' would require drilling some extra adjustment holes, and would result in the bulb projecting below the reflector, giving some glare. It would also cut off some light from potted plants arranged around the edge of the water. If you have the money to spend, go for 1000w, which should give in excess of 1000fc at 3'. The light level of the present halide lamp at the water surface is about the same as that measured at a distance of 6" from two tubed 4' fluorescent light fixtures. Five or six of the fixtures would be required to cover the same area, with no light available for peripheral plants, at the same total wattage now used.

The foot-candle (fc) is the standard unit of measurement for light intensity. The variability of light intensity is enormous, and the human eye is a very poor judge of it. Foot-candle meters are available, and when used in conjunction with the standard 18% gray scale card (available from photography shops) the intensity can be measured. For those who do not have access to this equipment, approximate readings can be made using a SLR camera and a piece of white typing paper. Set the film speed to ASA 25, the shutter speed to 1/60 sec and use Table I to determine the amount of light reflected. Focus is not important. The distance used should be such that the entire field of view is covered with the paper - about a foot. The gray scale card results in readings about 2 f-stops darker, and should not be used with the table. A little experimentation with different locations will show just how variable light readings are. Table 1 is the result of averaging all the literature I could find on similar tables. It should allow for differences in cameras, paper reflectivity and other variables that you will encounter. If you have a foot-candle meter, so much the better.

Table 1: Table to Use Camera as a Light Meter (ASA 25, 1/60 sec)

 F-Stop  Foot Candles
 2.8  108
 4  219
 5.6  430
 8  877
 11  1660
 16  3512
 22  6639

Frangipani in the grow room
Results: With the timer set to provide about 12 hours of light, the plant room temperature is 80-85°F and the humidity is about 50%. The water temperature in the lagoons is 75°F. At night, the room temperature drops to about 75°F, being held there by the mass of water. Growth of the peripheral tropical plants under the fluorescent lights is better than they achieve outdoors in the summer, possibly due to the lack of cool evenings they encounter when outdoors. One of the frangipani is now in bloom.

Nymphaea 'Mrs. Martin Randig' day bloomers generally have one or two blossoms each, and although smaller than in the outdoor light level, they nevertheless fill the room with their sweet scent. The two Nymphaea 'Mrs. Emily G. Hutchings' night bloomers take turns blooming, with one flower each. Water hyacinths grow well and bloom occasionally, but would do much better if it were not for the goldfish eating the roots. Water lettuce also thrives, although the goldfish eat the roots of this as well. Incidentally, I have found that water hyacinths and water lettuce just do not mix with goldfish, because of this problem. For the best looking plants, even outdoors in the summer, I always separate them, except during spawning time. Next winter, I swear I will bring no goldfish indoors. In the late winter the room becomes very crowded with flower seedlings and tomatoes being readied for spring planting.

I have had very poor results with lotus -- even the hardy ones -- because of the short season. This year I am going to try to "jump start" one by bringing it out of cool storage in February and placing it in the "greenhouse". This is not a completed project. There remains much room for experimentation of all kinds. The temptation to add varieties, increase the light level and add more shelving is always there. But my original goal of extending the hobby to four seasons has been achieved.

Growing Plants Under Artificial Light -- In Retrospect

Although I in no way wish to take away from the above experience, I think it is important to say, in retrospect, that unless one has a fortune to spend in measuring equipment the measurement of the light used is at best a trial and error situation. Table 1 will get you in the ball park, but don't spend a lot of time with your light meter trying to achieve certain foot candle amounts. Why? There are two main reasons:

1. The intensity of light varies with the inverse of the square of the distance between the light and the subject. That means if the distance is doubled the intensity is divided by four!! If you are doing things in a relatively small way, you barely have enough light to do the job from a distance of a couple of feet. In the case of fluorescent lights you are talking a few inches. Under those conditions it is easy to lose a lot of your light just by moving the bulb distance a small amount. You also end up with the situation where the top of the plant is at an intensity many times that of the bottom. If you were in a commercial greenhouse situation the light would be applied from several feet overhead and variations in distance would not result in such a great difference.

2. This one is more complicated. Sunlight is an extension of the electromagnetic spectrum -- radio, radar, microwave, etc. The different colors of light relate to frequency and they each have different intensities, or amplitudes. The atmosphere acts as a filter, depending on how far the light has to travel to get through it, and it affects the different colors in different ways. The altitude of the sun in the sky, as it varies from June through September presents a slightly different spectrum to the plants. Some think that the red-shift in the spectrum, along with the shorter days, affects the maturing of plants and the ripening of seeds. For this reason some will use sodium vapor lamps, or a mix of metal halide and sodium vapor to achieve a red-shift in the applied light and improve flower-heading and seeding characteristics.

In normal sunlight, the different frequencies (colors) have about the same intensity, and light meters are designed to measure the AVERAGE of the various intensities, i.e. meters are designed to measure sunlight. But different types of light sources do not produce light having the same uniformity of color intensity as sunlight. In addition, plants do not respond uniformly to the different colors of light, so light source manufacturers will try to tailor the bulb to produce what the plant wants. The net result is that different light sources -- incandescent, fluorescent, special plant growing fluorescent, metal halide, sodium vapor, etc. -- have different shaped intensity curves. In the meantime, the light meter is reading AVERAGE.

Without agonizing further, suffice it to say that with only a little experimentation you will arrive at a satisfactory solution to your situation. In many respects I got better growth and blossoms, especially with low-growing water plants, in the basement grow room in the winter than in the outdoor greenhouse, because the outdoor greenhouse suffers from low light intensity and short days. It is likely that supplemental lighting in the greenhouse will be necessary in the winter just to keep a few of the water plant species alive.

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