Whilst it is best to use specialized greenhouse equipment to build your homemade indoor greenhouse, not everyone can afford to do so. But not to worry, since it is possible to make a working indoor greenhouse using everyday items that you can find in any hardware store, supermarket or building materials supplier.
A Simple Homemade Indoor Greenhouse for Potted Plants
The following technique is best used for overwintering potted plants, to keep them warm when waiting to transplant them to your garden. You start the process by building a table. To do this, all you will need are some four by twos for the legs, something to affix the legs to the ground and a sheet of exterior grade plywood, four feet by eight feet. Or if you have a ready made table that size, you could use that, though it still needs to be fixed to the floor to minimize disturbance to your plants.
If you use plywood, make sure that the top side is sanded and painted or varnished, to repel standing water from the surface of the table. This table will hold up to 18 trays of 72 small pots each. Now, all you need is a thermostat placed in the middle to regulate heat, and a source of light. It doesn’t have to be special indoor greenhouse lighting; eight double 40-watt fluorescent lights on chains will do the trick. You will need to water the plants yourself, since there is no mister or watering device in this design.
A Slightly More Sophisticated Design
If this is not enough for your needs, it is possible to make a homemade indoor greenhouse that resembles the mini greenhouses which you can buy ready made. For this, you will need to start by constructing a freestanding shelving unit of up to four shelves. Again, the unit will need to be fixed firmly to the ground somehow. Once this is done, you can retain heat and moisture by covering it with saran wrap, or even an old shower curtain, held together with duct tape. Heat pads can be bought in any drugstore and can be used to provide heat by placing them at the bottom of the greenhouse.
Make sure you buy a thermometer to measure the temperature in your homemade indoor greenhouse. You can give your plants moisture by placing a cup of hot water in the greenhouse, and light using an ordinary desk lamp. Halogen lights are not recommended for this purpose as they are expensive to run and give off harmful emissions. A 26W bulb is sufficient, though a higher wattage bulb is better.
Once you have some sort of container to hold the soil and plants on the shelf, a world of gardening pleasure awaits you in your homemade indoor greenhouse. Enjoy!