How to Grow Hydroponic Onions

Grow Hydroponic Onions

I’ve been interested in growing root crops hydroponically, but never taken the plunge.  There are a lot of things that you can grow in a hydroponic system, but there’s not a lot of information out there about how to grow onions, carrots, radishes, or any other root crop.  This is why I’ve started The Grand Onion Experiment!  Read on to check out the setup.


  • Onion sets
  • Air stone
  • Air pump
  • Water
  • Net pots
  • Growing medium
  • Tray

I picked up some red onion sets from my local Home Depot.  The rest of the materials I had from other grows, but you can source most of it from Home Depot and your local hydroponics or gardening store.  You can also improvise and make your own equipment – there are a lot of different ways to do it!

Choosing a System

I decided to go with Deep Water Culture for this experiment setup due to the unique growing requirements of onions.  I also am in love with the DWC method.  It’s a very easy method to learn and also produces some of the most robust harvests that I’ve ever seen.

In my setup I have six 3″ net pots filled to the brim with perlite.  I placed the onions halfway in the perlite and then put all of my net pots into a grow tray.  The only thing left to do was fill it with water and toss in an air stone.

Video Tour

YouTube video

If you’re going to replicate this hydroponic onion experiment, make sure you plant all of the bulbs at around the same height.  This way, you can pour in just the right amount of water so the roots are constantly wet, but the bulbs never touch the water.  I’m not sure how bad that would be, but I don’t want to risk any rotting or decay by having the bulbs sit in water.

Last Thoughts

I didn’t mention in the video that I have no nutrients in my water for the first week.  I read about this trick a few days ago.  The general idea is that by starving your onions at the start, you force the roots to grow a nice, robust system because they’re trying to find nutrients as quickly as possible.  Then, when you finally do add nutrients to the system, your onions have a very healthy, stable root base to help them grow HUGE!

Header image courtesy of SoraZG