Grow citrus indoors with 12 to 16 hours of supplemental light. You can get good growth and vigor from citrus using MH/CMH, CFL, or intense HO T5 lamps, but you’ll need a full-size grow lamp.

You can also place citrus plants inside grow tents with HID lamps for best production. If you have very bright south-facing windows, you may be able to combine that natural light with a few spotlight CFLs to keep a group of citrus happy in your living room.

Gardening Under Lights Book

Your setup will depend on your level of interest and commitment, space, and budget. You might use a combination of equipment and setups. Shelving, closets, and countertops all hold plants in my house.

Young seedlings, houseplant cuttings, African violets, medium-temperature orchids, and cooler-season vegetable crops occupy indoor areas at any given time year-round. I also have a couple of previously unused indoor closets that work nicely for tucking away crops that like a bright spot in the 65°F to 85ºF (18–29°C) range without exposure to very hot or cold temperatures.

Gardening Under Lights Book

If you're interested in gardening under lights indoors, it's good to have a basic understanding of photosynthesis. Photosynthesis is a reaction to a transfer of energy. Think of a plant’s leaves and green stems as light-energy collectors; nature's very own solar panels.

Light hits the surface of a leaf or a green stem, and specific cells convert the light energy into sugars. These sugars move around the plant, driving various biological functions. A major by-product of photosynthesis is oxygen; hence, we breathe. When using indoor grow lights, your goal should be to provide enough light to fuel successful photosynthesis.

Gardening Under Lights Book

Depending on the crop you’re growing, temperatures that are too hot or too cold can hinder growth and development. Every type of plant has an optimal temperature range for producing healthy foliage and flowers. Temperature settings that are too high, coupled with no water, is a bad combination.

Temperatures for this orchid were too hot and it dried out and dropped all its leaves. Most of the canes have also died. Whoops!

Gardening Under Lights Book

The wattage of your lamp dictates the distance from plants. Lamps that are 150W are not very hot and can be placed within 6-8" of your plants, while 600W lamps need to be kept at a distance of 18-24".

My young naranjilla (Solanum quitoense) transplants, and Brugmansia cuttings, are growing about 6-8” below a 4-lamp T5 fluorescent fixture. As they get taller, they’ll need to be moved further away from the lamps or their foliage will burn.

Gardening Under Lights Book

Want to grow your own carrots? Carrots are generally easy to grow, under the right conditions. Direct seed carrots into the garden or growing container that you'll keep indoors. As with all root crops, carrots do not transplant well and need to develop right where they germinate. Sow seeds ½ 8 to ¼ inch deep. Once seedlings have emerged, thin them out so they are 1 to 2 inches apart.

Grow carrots with 10 to 12 hours of light from grow lamps indoors at cool temperatures to discourage early bolting. If your home is too warm or you do not air-cool a grow tent, a cool garage with grow lights is a good location.

Gardening Under Lights Book

Some of the newer, larger LED grow-light fixtures, especially those labeled for commercial production, produce a light that mimics the spectrum output of HPS lamps or HO T5 fluorescents, and they are marketed as low-energy replacements for both.

One limitation of LED lamps is that you cannot replace the bulb once it stops functioning. When a diode quits working, that lamp is kaput. Some manufacturers, however, claim their LEDs will last for upward of 100,000 hours and that you will never need to change a bulb.

Gardening Under Lights Book

Cool-season vegetables such as kale, lettuce, and spinach, and flowering plants such as cyclamen and snapdragons, grow best at temperatures between 50°F and 70°F (10–21°C).If you have a dedicated grow room or basement, you can install separate temperature controls for your space for warm & cool season crops, but you will still need some venting capabilities.

If you’re growing plants in a tighter enclosed space, such as a small closet or a sealed grow tent, pay close attention to the heat output of your lamp.