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Seeds Love This Simple Indoor Greenhouse

And so will you when you see the results of this easy greenhouse setup. Nearly all your seeds will germinate and grow into strong nursery-quality plants than ever before. What it amounts to is this: Providing seeds what they need for the best start possible, and then keeping their growing conditions consistently ideal. Seeds can’t help but shoot up, grow straight and strong, and be ready to flourish outdoors.

Once constructed, this little greenhouse will last from year to year, with only the change of light bulbs. You can use it year round, or only during the planting and growing season. It is easy. It is quick. Takes up little space. And it’s inexpensive. (I was able to afford it on a part-time income.)

I got the idea after trying — with little success — to start seeds indoors using window sunlight. The results were so poor I nearly gave up. But I was so poor, I needed to try some other way, since I couldn’t afford all the flowers I wanted to plant in my yard.

My failed experiment told me the most important ingredients for growing seeds indoors were the warmth, light and moisture. And above all these was consistency of those conditions. So, that meant some kind of controlled atmosphere – a greenhouse.

I drew a picture of what this might look like, where such things were available, how they would work together and whether I could build it and afford it — being not a carpenter and not rich.

Seeds Love This Simple Indoor Greenhouse
Indoor Greenhouse

The Results are The Indoor Greenhouse Step-by-step Instructions Below

Even on my first attempt at growing seeds in this make-shift apparatus, the results far exceeded my expectations. Nearly every seed germinated in my little greenhouse setup, often in about half the time listed on the seed packet. Each seed that germinated grew to a healthy size in a matter of weeks. 

I started in February and March. By April and May, my seedlings were more than large enough to be transplanted.

That first spring and summer, I had more nursery-quality seedlings than I had space or time to plant in my own garden. I ended up giving away hundreds of plants! Even as a novice gardener, I was able to successfully grow petunias, marigolds, coleus, carnations, lavender, salvia, painted daisies, shasta daisies, campanula and many others in the greenhouse.

While escaping a huge bill at the nursery, I was able to plant my garden extravagantly, and then had the joy of presenting the leftovers to neighbors, friends and relatives.

If you’re still not convinced about setting up an indoor greenhouse, here’s one more reason: convenience. You escape weekend mobs at garden centers, plus the work of hauling everything home and then the rushing to get it planted before it wilts.

The last benefit is one you may not even notice, but is perhaps the greatest: you will learn a great deal about plant care, which will only make you a better gardener. So, find a spot for this little greenhouse. It can be in the basement, the garage (only if sufficiently warm during cold months), any spare room, even the kitchen – wherever it fits in your home.

You can make it as small or large as you want: two shelves, six shelves, two sets of shelving units; it’s all up to you. So, here are the directions, the materials you will need, and the approximate cost for creating your own indoor greenhouse.

Utility shelf (plastic or metal) $30 – $40
Shop lights (one or two per shelf)$8 – $10 each
Fluorescent light bulbs (two per shop light) $10 (2-pack)
Heavy duty light timer$10 – $15
Power strip$3 – $5
Extension cord (if needed)$5
Small fan$10


  • At the hardware store, home supply center, or discount store – anywhere you find the best price — purchase stand-alone utility shelves, either of metal or plastic. I prefer plastic shelves because they won’t corrode. Plus, they are lighter and easier to assemble and to move later. This becomes the frame of the greenhouse structure.
  • The shelves themselves should have grids or open spaces, allowing light and air to pass from one shelf to another. There are three reasons for this: 
  1. You need the openings from which to hang the shop lights on each level; 
  2. You want the light to diffuse and be reflected all around the seedlings; 
  3. You want the air to circulate around your seedlings as they grow, helping prevent “damping off,” mold and sogginess after watering.
  • Assemble the shelving near the place you intend to set up the greenhouse. Once large shelves are assembled, they can be awkward to move. Put the shelving near an outlet, or have a good quality extension cord handy to connect to the nearest outlet. Keep these away from foot traffic, pets and children, because the lights will be going on and off every day as your seedlings grow for several weeks.
  • For as many shelves as you intend to use, you will need at least one shop light. Two per shelf provide even more consistent lighting. Shop lights are inexpensive and usually made of durable plastic and don’t come with lights. You’ll have to buy them separately, so remember to pick up some fluorescent tubes — two per each shop light — when at the store. The shop lights should come virtually assembled. All you do is pop in the lights and attach the suspension chains that come with them. Shop lights can use either plain fluorescent bulbs (inexpensive and very long lasting!) or they can accommodate special “grow lights”. There are differing opinions about whether grow lights actually help. They also can cost about twice as much as plain fluorescent bulbs. I have tried both, with no visible difference in results. Grow lights emit a wider color spectrum.
  • Attach the chains of the shop lights and use them to hang the lights securely above each shelf. For the top shelf, suspend the light from the ceiling. For shelf lights, suspend from the above shelf. The chains also allow you to adjust the space between the lights and the seedlings as they grow. (More about that under Starting Seeds.)
  • After assembling the shop lights and hanging them from each shelf, it’s time to plug the separate light cords into the power strip. If you’re using a set of tall shelves, it may be necessary to secure the power strip to the back of the center shelf so that all the shop light cords can reach it. Also, make sure the power strip, itself, has a cord long enough to reach the outlet. Plug each shop light into the power strip. To test, plug the power strip into the outlet, flip the switch to “on” and make sure all the lights are working properly. Then, unplug the power strip.
  • Next, program the light timer for the hours you want all the shop lights to be on, and the time you want them to go off. This should be 12 to 18 hours a day, even when seedlings are just starting. Don’t worry about the power usage. Fluorescent lights use a great deal less power than incandescent bulbs. They also stay cool, even being run all day. This isn’t too much light for the plants. Fluorescent light is much less intense than sunlight.
  • Plug the timer into the outlet and plug the power strip cord into the timer. If you want to test the timer, let the setup run for a day before you put any seed flats in it.
  • Place covered seed flats on the shelves in any formation that fits and that gives each tray adequate light. Make sure the lights are on the seed trays right away. This provides a mild warmth that will help spur germination. Check the light timer in the first day or two to make sure it is operating correctly. Adjust the level of the lights so that they are just above the tops of the clear plastic covers on the seed flats. Do not let the light bulbs touch the plastic covers.
  • In five to ten days, you’ll begin seeing tiny green sprouts. THIS IS IMPORTANT—once the majority of seeds in a flat have sprouted, REMOVE the cover. This allows air circulation, which helps prevent mold and “damping off” disease, which kills new seedlings. After removing the covers, adjust lights downward to about two inches above the tops of the seed flats. Tiny seedlings need to be close to the lights in order to grow fast and strong. If the lights are too far away, the seedlings will grow stringy trying to reach it. You will move the lights upwards as the seedlings grow.
  • Water seedlings when the surface of the planting medium feels dry. This is about every two to five says.

CAUTION: Never let the planting medium become less than moist. (See Starting Seeds for details on caring for seedlings.)

  • As seedlings grow, make sure the lights stay at the right distance and that no plant is straining to get enough light. You know this when you see seedlings leaning in one direction. Either adjust the lights or rotate and move the flats around the greenhouse shelves so that each plant gets adequate light. Check the lights occasionally. Replace burned out bulbs immediately.

HINT: As seeds grow, gnats sometimes develop, even from the “sterile” planting medium. To control them, use flypaper or other sticky materials made for this. They are inexpensive and work well, without chemicals. Sprays would likely damage or kill tender sprouts.

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