Fluorescent Lights, Seeds, Transplants

What to do on a cold January day?  I think I’ll finish replacing my old T-12 fluorescent fixtures in my light box with some new T-8 troffers (commercial ceiling fixtures) that I purchased at a big box store last week.  In 2013, I raised all of my vegetable and annual flower transplants under a set of T-12 fluorescent fixtures which I have used for over 30 years.  But, T-12 fluorescent tubes are getting harder to find and the ones that are available at reasonable prices are 34 watts and only produce around 2,000 lumens. To raise healthy transplants, I found that a lumen rating of around 2,600 is necessary.

So, last Thursday I went to a big box home improvement store and purchased 4 2 foot by 4 foot T-8 troffers  (without fluorescent tubes for $42 each) to replace 8 1 foot by 4 foot T-12 strip fixtures.  T-8 fixtures use 32 watt fluorescent tubes ($3 each) and I installed 2 warm white tubes (6100K) and 2 cool white tubes (4100K) which have ratings of 2,550 and 2,600 lumens, respectively.  While cool white tubes (blue/green spectrum) by themselves will raise good transplants, I believe the addition of red spectrum light provided by the warm white tubes produces better transplants for me.

To install them, I had to connect about 4 feet of 3 wire 16 gauge wire ($1.50) and a three prong plug ($5).  So for a total investment  of about $60 per installed troffer, I can raise 4 flats of plants.  I use my lights continuously from late January through the end of July to produce transplants not only for the initial planting of vegetables and flowers, but also to have transplants available for when a space comes open in my garden.  For example, about June 15, my spring broccoli and cauliflower are spent, so I’ll have transplants of say zucchini ready to fill that hole in my garden. 

Remember that fluorescent lights lose some of their brightness as they age.  The T-8 tubes I purchased have a rated life of 20,000 hours, but will lose 10% of their brightness during the first 10% of their life.  Because I use my lights about 180 days a year for 16 hours a day (or 2,800 hours) a year, I replace my fluorescent tubes on an annual basis.  If your seedlings are looking leggy and you have the lights within an inch to two inches from the top of the seedling, try replacing the fluorescent tubes with some new tubes with at least a rating of 2,600 lumens.

If you are interested in seeing a picture of my light setup and reviewing an earlier (more in depth) blog I wrote on growing transplants under fluorescent lights, see my blog dated February 1, 2013 or search for “lights”.  You can also view a quick video on seed starting by clicking on this link.

4 Comments on “Fluorescent Lights, Seeds, Transplants

  1. Hi Kent,

    My system is not as well thought out as yours, but it works: Shop lights, fluorescent plant grow lights, Ikea moveable book shelves, heat mats, power strips and timers.
    The onions have germinated already. The goal is to grow enough to supply the Harvey household with enough onions to last the entire winter. They taste so much better than what is available in the store. And yes, we eat a lot of onions!

  2. I”m impressed, Sabine. I know the size of your garden and the thought that you could produce enough onions to last your guys all winter is mind-boggling. WHat kinds are you planting?

  3. I'm right behind you on this Kent. I'm ready to replace my T-12 fixtures with T-8s. Are you supporting your new lights from 2 points or 4 points. And did your fixtures come with a cover or safety grid you had to remove?

  4. Thanks for the detailed information, Kent. I need to upgrade my seed-starting setup, and you've made it easy.

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