Growing Onions Inside A Water Bottle In Your Kitchen Is Actually Pretty Simple

Onions are one of the easiest vegetables to grow, even for inexperienced gardeners. And if you don't have a garden, you can still grow them on a windowsill by using an empty plastic bottle as a budget-friendly way to keep them handy year round. 

The easiest way is to regrow green onion roots you would otherwise discard. Save about an inch or two from the white part, with the roots still attached. Then take a 12 or 16 ounce water or soda bottle, remove the label, wash it thoroughly and cut it in half. Place the green onion bulbs inside the bottom half of the bottle and add just enough water to keep the roots covered. Put the onion bottle on a sunny windowsill and change the water every two or three days. 

After a few days, green shoots will start growing. You can start harvesting when they are around four to five inches long, using scissors to cut as much as you need and letting the bulbs growing. This is especially great if you use green onions or scallions often. However, the plants will run out of nutrients when growing in water; plant them in soil after they regrow two or three times. 

For a super cool project, turn that plastic bottle into a tower to grow green onions — and even full-size onions — vertically on a windowsill. Green onions like full sun, but will grow well in partial shade; however, bulb onions will need plenty of sunlight to grow indoors, so find the sunniest location in your home.

Carefully cut three dime-sized holes, spacing them at an even distance from one another around the bottom of the bottle. Then move one to two inches up the bottle and cut another row of three holes, staggering them so they do not line up directly with the holes in the row below. Continue this pattern, creating additional rows upwards.

Use a funnel to fill the bottle with potting soil and insert the green onion roots into each of the holes at a slight upward angle. Place the bottle over a drainage tray on a sunny windowsill and water well. You can harvest the green stems as before, or pull the whole onion when it reaches the size of a pencil, and replace it with another onion root. Keep the soil moist, but not damp, so the onions don't rot.

For full-size onions, use a gallon bottle and cut off the top off where it tapers. You can purchase onion sets of different types of onions, or regrow them from onions that sprouted in your kitchen. Depending on the size of bulb you wish to harvest, leave more or less space between the holes. Add a layer of soil just below the first row and poke the bulbs through with the stem side facing out.  

Keep the onions moist and feed them once a month when watering. Turn the tower every few days to ensure all onions get enough light. When ready to harvest, dump the whole thing out and start over with your onion tower.