Did you ever want to grow your own food? Indoors and without soil? You can…with micro-hydroponics!
Micro-hydroponics allows you to grow miniature vegetable plants (less than 12 inches tall) hydroponically (without soil) in your house, apartment, garage, or lanai. The simplest setup involves a container, seeds, growing medium, nutrients, and light source—and if you don’t have the store-bought kind, you can substitute inexpensive household items.
Got quart or half-gallon cardboard milk or juice cartons? They make excellent containers for growing mini vegetables. Make sure your cartons have a screw cap spout. This makes it easier to add nutrient solutions to the carton, which can be done with a funnel. Cut a hole in the carton large enough to support the cup that holds the growing medium. Make sure the hole is a little smaller than the rim of the cup, so it doesn’t fall in.
Growing Medium & Pots
As plants grow higher, their roots grow lower, and they need something to hold onto. That’s the growing medium.
Foam cubes, like Oasis Cubes, provide an ideal growing medium to germinate vegetable seeds and grow plants. If you can’t find them at a local store or online, alternative growing media include vermiculite, perlite, clay pellets, coconut fiber (coir), or pine wood shavings.
You’ll also need something to hold the growing medium inside the milk cartons and support the seedlings. Small plastic pots like Net Pots are excellent because they have vertical slits on the sides to allow the roots to grow through into the nutrient solution. An inexpensive alternative is small plastic cups with vertical slits cut into the sides.
Vegetable seeds can start to grow directly in the growing medium and pots before they’re inserted into the containers. Fill the cubes or the pots partway with growing medium, place on a tray, and plant 1–2 seeds in each one. If you’re using cubes, just insert the seeds into the hole in the cube. Add enough water to thoroughly moisten the medium and pour off any excess. Cover the tray with a clear plastic lid or tent it with plastic wrap. Make sure to leave enough space above the cups or cubes for the plants to sprout.
Did you know? The University of Hawai‘i Seed Laboratory continues to operate during the COVID-19 crisis. High-quality seeds for Hawai‘i’s unique growing conditions can be ordered by mail, email, or phone—and delivered right to your door. Contact the UH Seed Lab at (808) 956-7890, (808) 956-2592 (fax), or email@example.com. Also check out the Hawai‘i Seed Growers Network, run by CTAHR’s GoFarm Hawai‘i farm coach Jay Bost, which offers great “local seeds for local needs.”
Special hydroponic fertilizers are available from local stores or by mail order. But any general-purpose, water-soluble fertilizer for vegetables is fine. Each one has a different strength, so closely follow the manufacturer’s directions when mixing the nutrient solution.
Vegetables need a lot of light, so if you’re growing them indoors, they’ll do best with artificial lighting. The two best light sources are T5 high-output (HO) fluorescent lights and light-emitting diode (LED) lights.
T5 fluorescent lights are extremely bright compared to the typical T12 fluorescent lights used for room lights or shop lights. LED lights have come down in price quite a lot. They’re efficient in producing bright light, with less energy used and lower electric bills.
If you can’t get T5 fluorescent or LED lighting, place vegetable plants near a window that gets direct sunlight during the day, or try a bright household lamp.
By the way, my first experience growing vegetables indoors was lettuce grown on top of my office file cabinet. Because the room light wasn't bright enough, the lettuce started to change shape into a vine, and it grew down along the side of my file cabinet—all the way to the floor! That’s when I realized that lettuce and other vegetables need much brighter light.
Now sit back and relax, and let the vegetables do their thing. As they grow, periodically add nutrient solution to the milk cartons with a funnel so the cartons remain about ¼ to ½ full.
For more tips and how-to’s, please visit my Micro-Hydroponics website.
Stay safe out there!
Dr. Kent Kobayashi, Department of Tropical Plant and Soil Sciences, UH College of Tropical Agriculture and Human Resources