Building a seedling rack


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seedling_rackthumbHaving a seedling rack with heated pads and special grow lights to be able to sprout and grow your seedlings indoors is, while not a requirement of Square Foot Gardening, most definately a bonus. In this way, you can grow your seedlings throughout the year.

What you do with those seedlings during winter is then up to you. We will be growing as many of them as we can in a variety of pots, barrels and even in an old metal bathtub. Those seedlings that we do not have enough containers for, we’ll put out into the SFG boxes, test various methods of keeping them warm and protecting them from frost and just generally see what happens to them.

Building the seedling rack in itself was pretty easy but trying to find suitable heating pads and grow lights was a little more difficult. I found a picture and basic plan online, popped in to my local builders warehouse for some wood and screws and put it all together in a couple of hours one night.

I did a fair bit of research to find out about special growing lights for seedlings and came away even more confused than before. There is a lot of conflicting information out there on this topic. I eventually went with the information provided by the guy who designed the growing rack and decided to go with two 2ft (double) fluorescent light fittings (for two of the shelves) with a ‘Cool White’ and a ‘Wide Spectrum’ tube in each fitting.

Only after I had purchased the fittings did I find out how difficult it was to find the ‘Wide Spectrum’ tubes. Most people didn’t have a clue about what I was talking about until I specifically mentioned that they were used for growing plants… “Oh, Grow Lights” they said, “well why didn’t you say so? Yes we do sell them but they are out of stock“. Everywhere I tried was “Sorry, out of stock“. I have a few 2ft ‘Grow Light’ tubes on order now but who knows when they will come through. And, I still don’t know if these ‘Grow Lights’ are the same things as a ‘Wide Spectrum’ tube šŸ™

So for the moment I am just using plain ‘Cool White’ tubes and I must admit that the seedlings are still doing very well under these globes. It will be interesting to see the difference that a ‘Grow Light’ tube would make, if any at all.

The heating pads were another story altogether. Most of South Africa does not have the same harsh winters as found in the USA, Canada and across Europe so we therefore also do not have the same range (and cheap pricing) of heating products in our country that is commonly available overseas. I came across one or two small, really expensive heating pads specifically designed for seedlings but, due to the prices, I decided to expand my search into various other markets too.

I thought of underfloor heating and spoke to a few people in the industry but it gets rather complicated when you start working with thermostats (they get pretty hot), waterproofing and coverings, sizing etc. I did however, find a 60cmx40cm heated ‘Foot Mat’ at builders Warehouse for R350 – no thermostat, just a low and high setting. I bought it to test.

Then I looked at the pet industry (fishtanks and reptiles) and found a few Reptile Mats in various sizes that could possibly work. Again no temperature settings but a little more waterproof than the Foot Mat so I bought a 35cmx35cm one for R90.

To make the Foot Mat waterproof I simply covered the top with a black plastic dustbin bag – overlapping it a bit on the bottom edges but leaving most of the bottom open so as not to ‘overheat’ the mat and burn it out. The Reptile Mat has a thin ‘foil’ covering so I am using it ‘as is’ (just being very careful not to tear the foil).

The ideal soil temperature for growing seedlings is between 24 and 28 degrees Celsius (depending on the plant) and I was a bit concerned that these heating pads would either be too hot or too cold. I needn’t have worried, at the pet store I also bought a ‘floating’ thermometer and have used it, pushed into the soil of a ‘blank’ seedling tray compartment, to test the soil temperature. A perfect 26-27 degrees when on the Foot Mat and a good 22-24 degrees on the Reptile Mat.

Here is our seedling rack (click on the images to enlarge):

Although I feel more like a carpenter than a gardener with all this building going on, my seedlings are now happy and therefore so am I šŸ˜‰

Happy gardening

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12 Comments on “Building a seedling rack”

  1. James Johnston says:

    Have you looked at the lamps for sale at aquarium shops. I am sure that you may find some thing better than a plain fluorescent lamp.

    • Mark says:

      Hi James
      I didn’t ever get my grow light tubes that were on order, I think they forgot about me šŸ™

      However, eight months down the line and my seedlings are still doing very well under normal cool white tubes so I am not really concerned about finding the grow lights anymore.

      • Riaan says:

        Hi,discovered your site and I find it very helpful. Thanx for all your effort. I found some “Grow LED bulbs”. They are a bit pricey, but they use next to nothing electricity wise and they are easy to install, just like a normal bulb. Make sure you select the correct voltage bulb. Have you thought about using those low consumption wall mounted heaters that Salton makes as a heat source?


  2. Peers says:

    Hi there every one! I’m in need of a cheap small growlight as part of my project! If any one can be a help pls do!!!

    email =

  3. Shingi says:

    Hi Peers
    Go to cashbuild – they have fluorescent casings for about R150

  4. Nicki says:


    Exactly what bulbs did you use for your seedlings. I am having the same difficulty sourcing Grow Lights.


    • Mark says:

      Hi Nicki
      I waited for so long trying to find grow bulbs that I simply gave up and used normal fluorescent bulbs. Works like a charm but they have to be close to the plants.

  5. David says:

    Hi All,

    For those looking for grow lights, I use those supplied by Fish shops for planted Aquariums and they work very well, you get Blue, Red and White, the White are broad spectrum and should be used.

    Just ask the folks who work there they will give you the correct ones. Just a note they range from cheap to expensive, some even have reflectors which increase the directional light output. I personally started with the cheap ones at about R50 for a 25w from Boyu.

    Good Luck!

    • Mark says:

      Thanks David, that’s a source that I never even considered. Next time I’ll be sure to check them out and I’m sure it will help others as well.

  6. Julian says:

    Hey Mark the term ‘grow lights’ is a complete misnomer when you are dealing with seedlings. Cool white ( that is light with a temperature of +- 5000k) is not only ideal for vegetative growth but also widely available – and cheap. You could even use regular cfls, although strip lights are better in terms of light distribution, because of their shape. Broad spectrum is unnecessary unless you want to fruit indoors – but that is a completely different story.

    Great blog!

  7. Elize Rogers says:

    Hi Mark, just read through your article. Can you please direct me to your supplier of the 35×35 heating mat?

    • Mark says:

      Hi Elize, as per the post “Then I looked at the pet industry (fishtanks and reptiles) and found a few Reptile Mats in various sizes that could possibly work.” So you’d have to ask at a pet shop near you.

2 Trackbacks/Pingbacks

  1. Square Foot Gardening in South Africa | Planting our first seedlings 03 07 09
  2. Square Foot Gardening in South Africa | Growing Vegetables in Winter 03 07 09

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