Hydroponic lettuce, is it worth it?

Today I moved some lettuce seedlings from the propagator into one of the bus tub ebb and flow systems. As you can see from the photo, each tub will hold fifteen net pots. With three ebb and flow systems growing under my T5 fluorescent fixture I can grow forty five plants in about eight square feet.

I don't know for certain, but I estimate the cost of electricity for the T5 light to be about five dollars a month. In any event, it is not making a significant difference in our lighting bill.

The air and water pumps use about as much electricity as an electric razor, and only run for a total of one hour per day. The cost to operate them is insignificant, to say the least.

The time to grow a plant from seed to completion will vary by the variety, but on average it is about 35 days.

So let's assume, including nutrients, I am investing about eight dollars a month on energy and supplies. Let's assume again that with proper planning, I harvest twenty five plants a month. That means each plant is costing me about thirty two cents to grow to completion.

Factor in the quality of the lettuce; absolutely fresh, blemish free, pesticide free, never touched by animal feces, and an incredible variety not available locally.

From my point of view, growing your own salad greens is another no-brainer.

Low wattage LED seed propagation

The above photo shows my 13.5 watt LED grow light being used for seed propagation.

As the LEDs produce hardly any heat I can lower the unit to a few inches above the seedlings. The normal recommended operating height is six to twelve inches above the plants, however when it comes to light intensity, I feel more is better. I have changed the photoperiod to 14 hours to give the seedlings a chance to use the protein accumulated during the lighting cycle. My thinking is by lowering the lamp the increased intensity will compensate for the shorter photoperiod.

While surfing garden sites I find a lot of gardeners asking: "what kind of light should I use for seed propagation?" The most frequent response I see is 48" shop lights with warm and cool tubes. A 48" shop light with two tubes is using approximately 80 watts of electricity, compared to my LED grow light's 13.5 watts.

Hopefully, at some point gardening suppliers will make LED grow lights more available to gardening enthusiasts.

Just for fun

These two plants are really blooming nicely using the shorter photoperiod, UV light and 2700K compact fluorescent light.

The plant on the left is Carnation, Ipswitch Pink, and the plant on the right is an ornamental pepper started from seed in September.

I have never had success growing peppers in my soil garden, however my experience with this pepper plant is inspiring me to try to grow Poblano Chilles indoors.

LED Grow Lamp Evaluation

On January 7, 2009 two varieties of lettuce were started to compare the LED Grow Lamp to a Compact Fluorescent Grow Lamp for seed starting. The varieties are Brune D'Hiver and Gentilina, which have very similar growth patterns.

Both varieties were planted in rockwool cubes and received identical preconditioning and nutrients. A sixteen hour photoperiod was used for the compact fluoresent, and the seeds were placed in a humidity dome on a heating mat. The seeds under the LED grow lamp had a photoperiod of twenty hours, and were simply placed on a tray under ambient conditions.

As the photo above is labeled, the top row contains the seedlings grown under the compact fluorescent, and the bottom row contains the seedlings grown under the Red/Blue LED grow lamp.

For further consideration I would like to point out that the compact fluorescent is rated at 125 watts, and the Red/Blue LED grow lamp is rated at 13.5 watts. If my math is correct, that is a difference of almost ninety percent in energy consumption!

Aside from the energy cost; the compact fluorescent fixture and bulb, which only lasts a year, would be about $150. The small LED grow lamp, which has a life of fifteen years, cost me slightly more than $34, including shipping.

The seedlings grown under the Red/Blue LED grow lamp are further advanced, and are darker green in color.

Well, at least in terms of seed propagation, I am now a believer. I was impressed to the point that I have ordered a 90 watt LED UFO grow lamp for indoor growing and supplemental lighting for the greenhouse. The 90 watt LED is equivalent to a 400 or 600 HPS, and covers a growing area of 12 square feet. Additional advantages are that you do not have to change bulbs for the growing and flowering cycles, there is no ballast or ventilation to deal with, and it has a life span of more than 60,000 hours. Basically, it is a no-brainer.

Adding UV to plant lighting.

The Carnation mentioned in my previous post of bending the seasons, and illustrated in my 12/30/08 post, has flowered. This variety is Dianthus Plumarius, or Ipswitch Pink.

It progressed from just forming buds to bloom in one week, however, I can not attribute the blooming to just the addition of UV lighting. In addition to adding the UV LEDs, the photoperiod, temperature and Kelvin temperature of the lighting were also changed.

A future project will be to use the UV lighting with the LED grow light to grow a Calceolaria to completion. I have two plants about the same size, and I will grow one under T5 fluorescent, and the other with the LED and UV lights for comparison.

This should prove interesting!

The above photo is not a UFO, it is the LED grow light I will be testing to determine if it does grow superior plants, or any plants at all for that matter.

Being an eternal optimist, I have complete faith in this project. Well, almost complete faith.

The first test will be to compare it to fluorescent lighting for germination of seeds. I have been using full spectrum 6100K fluorescent lighting for seed starting. For this trial the LED light will be suspended three inches above ten rockwool cubes planted with lettuce and flower seeds. The initial photoperiod will be 20 hours, however, I have never tried that long a photoperiod. I have read that some commercial hydroponic lettuce growers use a 24 hour photoperiod for seeds, so 20 hours seems reasonable to try. It will certainly add some mood lighting to my growing area at night.....

It just seems like a good idea, and this light produces hardly any heat at all, and is super super super energy efficient.

Again, time will tell.

Cassandra lettuce

It is becoming more apparent to me that some varieties of lettuce grow exceptionally well hydroponically.

This particular plant, Cassandra, was started from seed on 11/20/2008, and on 1/3/2009 it is almost ready to harvest. Of course, individual leaves could have been taken from the plant while it has been growing.

The leaves on this plant are very soft to the touch, and I am guessing that it is going to be very tasty indeed!