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
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!
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.
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.
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.
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.