How To Germinate Hydroponic Seedlings


When discussing hydroponic growing for beginners, an often overlooked yet crucial step is where to get the plants from. A popular option for beginners who want a truly authentic DIY gardening experience is to start from seeds. It takes longer of course before you can enjoy the fruits of your labor, so to speak, but the process could be just that much more enjoyable.

You’ll also have a better appreciation when your plants reach maturity. Not to mention, it’s quite educational as well to start from mere seedlings. When you germinate hydroponic seedlings, you also prevent bringing pests and diseases into your controlled growing environment.


Grodan Rockwool Cubes for germinating hydroponic seedlings.

Techniques to Germinate Hydroponic Seedlings

In traditional gardening you can place seeds directly into soil to begin sprouting. However, in hydroponics you cannot place seedlings directly into the grow medium. They won’t take hold or they could be washed away by the nutrient solution. Instead you need to begin to germinate hydroponic seedlings externally from the hydroponic garden.

When you germinate hydroponic seedlings they need a lot of moisture in order to sprout. Seeds also need warmth (around 70 degrees or more) and bright light in order to be brought to life. To get started, it’s recommended to use grow mediums specially designed for seed germination. Rockwool cubes are good for this. They retain moisture and break apart easily to insert seeds.

If you’re growing multiple plants, you can create a “nursery” by placing several different rockwool cubes of seeds in a grow tray. Place the tray in a brightly lit area. Make sure to keep the grow medium moist while the seeds begin to sprout. You’ll notice sprouting a only a matter of days.

Transplanting Germinated Hydroponic Sprouts

Once the sprouts have reached about 3 inches in height and have multiple leaves, you’ll be able to transplant them in to your hydroponic garden which should already contain your grow medium of choice. You won’t even need to necessarily break the plant out of the rockwool. You can simply insert the cube directly into a hole in the grow medium of the garden.


Mondi Mini Greenhouse is a protected environment for germinating hydroponic seedlings. Image via

Post-Transplant Care Techniques

It’s recommended to water the plants from the top with your nutrient solution for the first week. This will prevent them from drying out and will give the roots time to grow downward.

Remember not to place your artificial lighting too close to the newly sprouted plants. You don’t want to burn them. Start grow lights up high and then lower them incrementally week by week until they are at the appropriate height – approximately two feet away from the plants.

Recommended Products for Germinating Hydroponic Seedlings

Grodan Rockwool Cubes: These retain water really well and are easy to mix in with other grow mediums.

Rapid Rooter Grow Plugs: These plugs keep moist and contain beneficial microbes which help condition plants’ root systems and fight off disease.

Mondi Mini Greenhouse: This provides a mini nursery for your plants during the early stages. It protects seedlings, traps in moisture, keeps them warm, and has ventilation.

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