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How to Build a Small Indoor Greenhouse

By Larry Parr ; Updated September 21, 2017

One of the keys to starting seeds or growing seedlings is to keep the temperature, light and humidity carefully controlled. One of the best ways to do this is with a greenhouse. When most people think of a greenhouse, they picture a large outdoor building covered with panes of glass. However, you can build a simple indoor greenhouse for under $100 that will start your seeds and help your seedlings turn into strong, healthy plants with very little effort.

Set up one or more plastic shelving units. These units can be purchased at any home improvement center or they can often be found at garage sales. Purchase units with at least three to four shelves.

Hang shop lights from the underside of each shelf. Shop lights should come with hanging chains to make this easy. Install fluorescent light bulbs in each shop light. The bulbs will need to be purchased separately. There is no need to spend the extra money on grow lights--regular fluorescent lights will do just fine.

Mount a power strip on the back of one of the shelves so that all of the shop lights on each shelving unit can plug into it. Attach the power strip to an outlet--use an extension cord if necessary. Turn on the power strip and test the lights to make sure all of them are working properly.

Set flats of seeds or plants on each shelf under the florescent lights. Place trays under each flat to catch any extra water. Adjust the lights so that they are approximately 2 inches above the surface of the seeding flats or approximately 2 inches above the tops of the seedlings.

Water well. Keep soil moist but not too wet as too much water can cause rotting of new plants.

Drape plastic sheets over the shelving units to create greenhouse conditions. Run lights 12 hours each day. As seeds sprout and seedlings grow, adjust the shop lights so they remain approximately 2 inches above the plants.


Things You Will Need

  • One or more plastic shelving units
  • Shop lights
  • Fluorescent light bulbs
  • Extension cord
  • Power strip
  • Flats for growing seeds or seedlings
  • Trays to collect water from the flats
  • Plastic sheeting


  • You can add a timer to this setup so that the lights are automatically turned on and off at 12-hour intervals if desired.

About the Author


Larry Parr has been a full-time professional freelance writer for more than 30 years. For 25 years he wrote cartoons for television, everything from "Smurfs" to "Spider-Man." Today Parr train dogs and write articles on a variety of topics for websites worldwide.