How To Start Seeds For Hydroponics

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By Alex Harris

If you’ve been thinking about delving into the world of hydroponics, you’ve come to the right place! Hydroponics is an alternative method for plants compared to the traditional soil method.

Using hydroponics allows you to make sure that your plants are still getting all of the healthy nutrients that they need, whilst allowing you to skip all of the clean-up and pest control that can come with soil.

Hydroponics also allows you to reduce the amount of water that you use to look after your plants, whilst still ensuring that they receive the amount of water that they need!

Hydroponics has a huge amount of benefits, and considering that it’s so easy to set up… what’s stopping you?

Also Read: How To Build A Hydroponic System

Equipment & Materials List For Germinating Seeds For Hydroponics

Starter Plugs Or A Starting Medium 

As you are growing your seeds without soil, you’re going to need to provide a substitute for them to grow in and push their roots through.

You have two options here:

  1. You can choose to use either a starting medium, such as perlite or vermiculite. Starting mediums like these need to be used in the same way that you would use soil.
  2. Or you can choose to use starter plugs. Starter plugs are made from a material that allows your plants’ seeds to grow, such as Rockwool (this is a highly porous material, made from spun rock). Starter plugs come in cubes and are quite spongey.

The great thing about starter plugs is that each cube comes with a hole in for you to place your seed, and unlike other growing mediums, you don’t need to completely uproot the seedlings to transport them into a different container.

With starter plugs, you simply remove the cube and place it into the pot or container that you would like your plant to grow in.

A similar option is to use rapid rooter plugs. These are also cubes, but they are made of organic material (or materials). This means that rapid rooter plugs can help your seed absorb nutrients, and also improve its root growth.

If you choose to use starter plugs or rapid rooter plugs, you’ll need to hold them in something. This is where net cups can come in handy, as they can hold a cube in each individual cup. For most plants, we recommend a 2-inch net pot. See our full buying guide and reviews for more options: Best Hydroponic Net Pots


Choose a container to hold your seeds. You’ll probably be starting quite a few seeds, so if that’s the case, try to choose a tray that can fit the net cups in the quantities that you need. These trays should be around five inches deep to ensure that you have enough space to do everything necessary.

You could choose to set a hydroponic cloner system up for your seeds. This could even include air pumps! If you’re just starting out though, we recommend that you use a simple tray to start.

Heating Mat 

Buying a heating mat for your seeds is optional.

If the area you live in is cold, your seeds might not receive the right amount of heat. If you live in a cold region, you might want to consider purchasing a heating mat.

When placed underneath a growing tray, the heating mat will help your seeds to sprout, as it can help to bring them back up to the 70-90°F region. If your area is often considerably less than this temperature, a growing mat will benefit your seeds immensely.

Grow Lights

Grow lights aren’t necessary for starting seeds with hydroponics, but they can come in handy. If the area you live in doesn’t receive much sunlight, then buying a grow light is probably a good idea. Likewise, if it is winter, you will naturally receive less sunlight and a grow light can act as a substitute for this.

It is important that when the seeds emerge from the starter plugs or starting medium, they receive sunlight within the first eight hours or so – but preferably, immediately. This is because the seeds have just used the last of their energy sprouting, and they need more light to refuel.

Grow lights can be particularly useful here because they can be set on a time, so if you’re not at home, or just haven’t been able to check on them for a while, you don’t need to stress about your seeds being deprived of the sunlight they need.


There are a variety of methods that you can use to provide your seeds with nutrients if you are starting your seeds with hydroponics. You could use regular hydroponic nutrients for this, but because you’re starting seeds, dilute them to half-strength, or you could use nutrients that are specialized for starting seeds.

There is a wide range of these types of nutrients available, and they can be used to encourage your seeds to germinate, as well as boosting root growth.

How to start seeds for hydroponics2

Step-By-Step Instructions On How To Start Seeds For Hydroponics

Step One: Start By Preparing Your Starting Medium

Most growing mediums need to be soaked with water so that they’re ready for your seeds. Depending on the type of medium that you’re using, you might need to add a couple of extra steps (for example, if using Rockwool, you should wash it in a mix of vinegar and water because of how high its pH is).

Rockwool and coil mediums should be put in fresh water for around an hour. If you’re using rapid rooter cubes, they only need to be moistened by a mixture of water and nutrient solution (mild) for a couple of minutes.

Step Two: Put Your Seeds In 

Although your starter cubes might only have one hole in each cube, it’s quite likely that you will have a few seeds that don’t germinate successfully. To avoid wasting any of your material, it’s a good idea to put around 2-3 seeds in each cube.

After you’ve placed your seeds, you can stick a cube into each individual net cup within the grow tray that you have prepared.

Step Three: Add Your Nutrients (And Your Water!) 

Next, make up a mixture of water and a low concentration of either blooming mixes or hydroponic nutrients.

Make sure that you fill the tray so that around half an inch of your starter cubes are submerged – but no more than this. If you add too much water, your seeds might rot instead. Always pay attention to the level of the water – if it decreases, then make sure to add more nutrients and water in the way described.

Step Four: Give Your Seeds Some Light 

When your seeds start sprouting, make sure that they have an adequate amount of light. If you’re using grow lights, bring the lights closer to the tray as the seeds begin to emerge – but no more than six inches. If you do not have a grow light, you might want to move them around your house depending on where the sunlight is the strongest.


If you used started plugs you can disregard this.

Once the roots of your seeds start to emerge from the growing medium or cube, you can transplant them. This might take a couple of weeks, or even sometimes as long as four. Make sure to water them as needed until their roots start emerging.

Remember when we told you to put multiple seeds in each hole? If a few of the seeds in the same hole sprout, choose the healthiest plant and remove the others.

Now, they’re ready for transplantation!

Make sure to transplant your sprouted seeds into a working hydroponic system for bigger plants – you should research and build one in the time it takes for your seeds to germinate.

You can carve a little bit of space out for each cube within this system and place your cube within the space, with the plant seedling still inside, before covering it slightly with a little more growing medium.

For the first few days after their transplantation, you should water your seedlings with a nutrient mix, from the top.

Final Thoughts 

Starting seeds using hydroponics is achievable for everyone, and completely worth it. The possibilities here are truly endless – and you don’t have to deal with any of the clean-up that comes with soil.

Now that you’ve learned how to start your own seeds with hydroponics, hopefully, you can see how easy it is to do it yourself!

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