Hydroponic seed raising

When I first started with hydroponics I had questions about seed germination. Majority of hydroponics information around seedlings and plantings uses cloning or cutting or seedlings. Majority of what I […]

When I first started with hydroponics I had questions about seed germination. Majority of hydroponics information around seedlings and plantings uses cloning or cutting or seedlings. Majority of what I grow is from seeds. This is important to me for a number of reasons.

  • I can grow heirloom varieties
  • I can save and swap seeds
  • I can practice succession planting

I will try to remember to write another post going into detail on the above points. But seeds are important. So when I was looking into hydroponics I asked, what about seed germination? There were options. One was using grow wool cubes or similar. But they are expensive, especially for non-commercial use – its a single use item and will end up being something like $1-2 per seed. The second option was to use Vermiculite and a weak hydroponics solution.

Bingo. Vermiculite is a mineral that holds water extremely well. As a seed raising medium it changes the game. It allows a lot of air to the seeds and seedlings, which promotes root growth. Here is a quote from wikipedia:

Seed germination: vermiculite, alone or mixed with soil or peat, is used to germinate seeds; very little watering is required. When vermiculite is used alone, seedlings should be fed with a weak fertilizer solution when the first true leaves appear. A tablespoon of soluble fertilizer per one imperial gallon (3.78 : 1) of water is the recommended mix – Wikipedia

Seeds have all the energy and nutrients they need to propagate, so my initial watering of my vermiculite is with just water. Once the first leaves show I add a very weak hydroponic growing solution.

The success I have with this system is extraordinary compared to any other system I have tried. I generally get 99-100% germination.

Disclaimer: Lets be real, this is when germination conditions are ideal for the season and temperature of the seeds. This isn’t magic. There are some seeds I will do extra processes to achieve germination for things such as passionfruit, beans etc. Some seeds are difficult or require conditions, where I meet these this system works.

Tools and materials I use:

  • vermiculite
  • 24-cell seed raising tray (insert and water tight base)
  • hydroponic grow solution (or liquid fertilizer)
  • grow lights (optional but best for strong seedlings)


Place liner in tray base. Note that one of the sections has had its bottom cut off. I use that square to view the water level in the tray and easily water without disturbing the rest of the tray.

empty tray

Pour vermiculite over the tray to fill the sections. It’s quite easy to pour and fill from the small bags. Sometimes I buy them in larger bags and put the tray into the bag to fill. It will depend in your supply and how it is packaged.

loosely filled tray

The next step is to spread out the vermiculite so it is roughly even. I then fill the tray through the cut section a few times with water until the water has stopped being absorbed by the vermiculite. This can take anywhere from 10-30 minutes and filling the tray 3-4 times. I just use plain water at this point as stated previously the seeds have everything they need to germinate and do not need nutrients until the first leaves show.

leveled tray

Once the water has absorbed the vermiculite will appear darker and feel wet to the touch. This is when I gently press down on each section to level it with the top of the tray insert. I then lightly press the center of each section with my thumb to make a small indent for the seeds.

indented tray

Next is seed time. Depending on what I am wanting to germinate I plant the seeds into the rows of the tray. For larger seeds I might only add 1 seed, for smaller seeds I will add 2-3. Generally I regret adding more than 2 as all will germinate and then I have to attempt to separate the seedlings or thin the plants. I should be more ruthless as it always seems a waste to thin plants as they have germinated and grown. 

seeds in here

I will then pour a small amount of vermiculite over the top to cover the seeds.

seeds covered

I keep rough notes of the seeds I planted and write up a small grid based off the unfilled section.

ignore the handwriting

The tray is then placed on my growing frame under lights. I will check the water level every few days and top up as required. Germination is usually quite fast with 3-4 days.

tray under lights