Build an Indoor Seedling Starting Unit

STARTING SEEDS INDOORS CAN GIVE YOU A JUMP on the season and let you get your hands dirty while it’s still freezing outside. But indoor seedling starting systems can be costly, especially if you need enough space to start more than just a few plants.

In this video post, I’m going to show you how to build your own high-quality seedling starting unit at a pretty reasonable cost. There’s no question, you can build your own for even less money than I’ve spent, especially if you’re not “handyman-challenged” like I am.

Although it’s not the cheapest way possible, my plan for the unit is reasonably priced, easy and fast to assemble. The three main components are grow lighting, heating and shelving.


Sellers of greenhouses claim that you can’t have too much light for your plants, so you should buy the best possible lights. On the other hand, most people who’ve posted on the Internet about seedling starting have said that basic shop lights will do.

I made the mistake of purchasing fluorescent aquarium plant lighting for my shop light fixture. I won’t do that again. Basic fluorescent lights cost less and are good enough.

In addition, I opted for a very inexpensive light timer. Some people don’t like to put their grow lights on timers. They figure that, without a timer,  they’ll be forced to visit their plants at least twice a day to turn the lights on and off. That’s one way to help ensure that your plants are getting enough water, etc.


Often, the best possible germination rates occur when the seed starting mix temperature is between 70 to 75 degrees. If your growing space is on the cool side, you can usually have much better success if you add a little heat to the seed germination process. I purchased a seed starting mat from Hydrofarm. As an alternative, see this post by David LaFerney on his site called The Door Garden that shows how to build a great heating unit from rope lights.


An easy way to suspend the lights over the seedlings is to buy chrome shelving, which is waterproof and reasonably attractive. Another way to do this is to stack a table on top of another table and suspend the shop lights using screw-in hooks. I opted for the shelving.

Here’s my complete list of items that I used for my seedling starting unit and the approximate cost:

  • Shop Lights from Home Depot ($20)
  • Heating mat from Hydrofarm ($28)
  • Chrome Shelves ($40)
  • Chains and “S” hooks (already had them) for suspending the lights
  • Tarp (already had it) for protecting the floor from water
  • Some type of fireproof insulating material for under the heat mat
  • Trays and plastic milk jugs for holding the paper pots with seedlings
  • Light timer (already had it, but probably cost $10)


Here’s a video showing you how to assemble the unit. 

Related articles you might enjoy:

1. My Plan for Seed Starting Mix
2. My “Kick Start” Seed Trading Package from DG
3. Getting More Out of Seed Catalogs



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16 Responses to “Build an Indoor Seedling Starting Unit”

  1. Tara
    February 1, 2011 at 4:17 pm #

    are you opposed to the aquarium plant lights because of the cost? Just wondering b/c I splurged on the more expensive lightbulb. They are still ok for my babies (seedlings) right?

    • February 1, 2011 at 6:18 pm #

      Tara — Thanks for stopping by. The more expensive lights will be good for seedlings. There might even be some marginal benefit, but it probably wouldn’t be worth the added cost.

      I’ve tried it with both types of light bulbs and I’ve had good results both ways. When I was researching this post, I checked out a number of message boards. Almost everyone who commented said that normal shop lights work just fine.

  2. February 4, 2011 at 12:06 am #

    I definitely want to make a grow light system!

    • February 4, 2011 at 6:51 am #

      meemsnyc — It’s easy to build a unit. If you’re a little more adept at making stuff than I am, you can make one even more cheaply.

  3. January 6, 2012 at 7:43 pm #

    cheers, nice video. I don’t now if i would have all the materials though.

  4. Stacy
    November 3, 2012 at 4:24 am #

    Thinking about doing this with my kids as a Christmas for their dad. Watched the video and just wanted to check to see if the wood planks you put under the Hydrofarm mat were for “fireproof insulating material for under the heat mat”. Thanks so much for the video. I think this will be a great present.

    • November 3, 2012 at 9:32 am #

      Hi Stacy — In my case they are not fireproof, although I’m pretty sure it would be difficult for them to start on fire. I think it would be a good idea to use something that would be fireproof instead of the wood, although I’ve been trying to think of what would be good and not conduct electricity and haven’t been able to think of anything. By the way, as a dad, I think this would be an awesome Christmas present.

  5. John Affayroux
    January 23, 2015 at 9:32 pm #

    Nice job! I took a slightly different route. I made a 3 tier unit out of plywood and 2x4s. It is unsightly but in te basement. Each shelf measures 48 x 33, giving me room for 6 standard 11×22 plastic trays. Each shelf has 4 shop lights on adjustable chains. The lights are plugged in to 3 power strips so I can turn 1 shelf on at a time. I only use 1 shelf to start seeds and as they start to grow I transplant them into bigger cells which takes more room and there more lights turned on. I built my on heater “assembly”. My middle shelf is 3.5 inches thick (think 2x4s on their side), spacers hold a 12 foot heating cable with thermastat in the center on the 3.5 inches. It goes around and around with the wires never crossing each other. The top is galvaniazed steel from a heating place, the bottom is plywood, the whole thing is filled with sand which evens out the temp. It does a great job for starting seeds and after I no longer n3ed heat, I unplug the heater and use that as a 3rd shelf.

    • January 23, 2015 at 9:49 pm #

      I really like your idea of adding sand to even out the temperature.


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