When I first grew plants in a hydroponic way, I never thought much about the roots. 

But when I looked at hydroponic roots, I noticed some unusual things (at least unusual to me!). 

The roots were all thin and spidery! 

This got me wondering about roots, so I decided to research into the question: how do hydroponic roots grow?

Roots in hydroponics don’t need to provide security in soil, so they spread out with thin roots to reach more water. A single root will pop out from a seed and spread through the medium, looking for water and nutrients. The top part of the roots absorb air, and the main part of the roots pull up nutrients and water. 

Healthy roots are critical for a healthy plant, so keep reading for tips on promoting root growth and the best nutrients for growing plants. 

hydroponic roots grow hydroponics

How To Promote Root Growth In Hydroponics

Promoting healthy root growth in hydroponics isn’t a one-stop shop, but there are several key tips to follow if you want your seeds to sprout well and plant to grow faster. 

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Keep Sunlight Away From The Roots

Sunlight is great for plants but terrible for their roots. 

While visible light is great for photosynthesis and essential for creating energy, the roots of plants don’t do any of this conversion. 

The direct exposure dries out the roots quite quickly. This is a killer for most roots as they need to stay hydrated all the time. 

New plants will die almost instantly with dry roots. 

Established plants can survive being dry for a little while, but it’s best to avoid the dryness if at all possible. 

The heat and sunlight will also encourage bacteria and fungal growth on the roots, which will make them sick. 

This is especially true of moist and humid areas, and the interior of hydroponic systems is packed with water and humidity. 

Most people block the sun from their hydroponic solution and roots rest by covering the jar or using plastic to block and reflect the sun. 

Use Humic Acid

Roots will grow on their own when given nutrients, water, and the right temperature, but sometimes a little help goes a long way. 

Humic acid is one of those little bits of help we can give them. 

Humic acid is the condensed and fully decomposed remains of organic life. 

In the chemistry world, they’re a long chain of molecules. 

The acid is black and latches onto the nutrients in the solution, making it easier for the roots to absorb.

I don’t know much about that, but I know humic acid is amazing when it comes to helping roots grow. 

Add some to your nutrient solution, and it’ll increase the water retention of the roots and boost root growth. 

General Hydroponics humic acid is designed specifically for soilless systems, but it works just as well for traditional soil growing. 

Use Less Nutrients At First

On the other end, some people succeed by starving their new roots a little at first. 

This is a somewhat risky tactic and should only be attempted after the seedling has gotten a decent sprout. 

The theory behind this tip works well, and I’ve tried with some success (and some failure). 

If your plant is denied a lot of nutrients, it’ll seek to collect more. 

How do plants collect more nutrients? It grows its roots out farther, seeking what it needs. 

With hydroponics, the key is to lower the nutrient level in the water without lowering the water level. 

Hydroponics roots need constant water, or they’ll dry out and die almost instantly, especially if they’re young plants. 

You don’t want to deprive them completely of plants. 

The ratio I’ve found that seems to work the best is to cut the amount of nutrients used in half and re-up the nutrients after 3-7 days regardless of whether or not explosive root growth is happening. 

Add Fulvic Acid

Fulvic acid is another root growth substance similar to humic acid. 

Fulvic acid is considered a type of humic. 

This acid is made from decomposed plant matter specifically, and it’s normal yellow-brown. 

Fulvic acid also can increase water retention and the efficiency of nutrient absorption by the roots. 

But it features a unique ability to remove toxins and heavy metals where it’s used. 

This detox is why it was used as a medicine in the past and why some people use it as a health supplement today. 

Source: Healthline

Some soil, peat, coal, compost, and bodies of water contain high levels of peat. 

It’s very organic, naturally occurring, and great for root growth. 

Mr. Fulvic is a perfect example of this for hydroponics, and it’s good to use at any stage of growth. 

Use Rockwool For A Growing Medium

Rockwool is popular as a hydroponic growing medium, but its strength shows off the most in helping seedlings and new roots. 

Roots need water and stability, and Rockwool provides both of these in great amounts. 

The medium is made of loosely spun fibers, allowing for root growth and stability in a soilless system. 

Rockwool’s same fibers have an amazing water retention ability and draw the water close to the new roots, helping them get their footing. 

Use these Rockwool cubes for starting and growing your seeds, then break them up to provide more growing medium as the plant gets bigger. 

When you’re done with it, chop it out and bury it in your compost or outdoor soil garden for increased water retention and reuse. 

Check out our guide on how to use Rockwool for hydroponics

Keep The Temperature Ideal For Growth

Roots are sensitive, and this sensitivity impacts its temperature needs too. 

While some plants will grow at extreme temps, most plants need mild weather to proliferate quickly. 

As a general rule, the ideal temperature is between 65-75° degrees Fahrenheit (24° C). 

Some people use a heating pad to keep the air warm near their seedlings, while others just trust the normal temperature of their home. 

Whichever you use, make sure you have some means to track it and keep the plants away from heaters or air conditioners. 

These will dry out the plants quickly and kill them off. 

Heating pads are better for giving heat without drying out the air. 

Remember, light is the enemy, and so are light-based heaters. 

At least, this is the case in the initial growing stage. 

It’s common for seedlings to be grown completely covered up to trap humidity and prevent light from drying it out. 

Use Starter Nutrients For Your Hydroponic Solution

All of the above tips are more natural and should be enough to give your roots a good chance at growing well. 

But if you want something a little more or you need help, a starter solution or root enhancer is a viable option. 

These are often more expensive, but they’ll make a huge difference in your root growth. 

Fortunately, a little goes a long way, so even though you spend more, you get more out of the product than you’d expect. 

This Rapid Start Root Enhancer is one of the best out there.  

Best Nutrients For Root Growth

Plants need a lot of nutrients, but some stick out when it comes to their root growth. 

When picking nutrients for root growth, make sure it uses them in higher amounts. 


Phosphorus is the best nutrient for growth. 

It’s largely responsible for converting energy into growth, so roots need a lot of this. 

Established plants don’t need it as much (though it’s always good for plants). 

A lack of phosphorus stunts growth, delays maturity and lessens yield. 

It’s shown as a “P” in most chemical symbols. 


Potassium is the next critical nutrient for plants. 

Written as “K” in chemical symbols, potassium is critical for plants at all stages of life. 

It’s largely responsible for activating many processes involving energy, including photosynthesis, which is how plants create energy in the first place. 


Nitrogen (N) wraps up the “big 3” of all plant growth. 

With roots, it’s less critical, though still needed. 

In a starter solution, you may see an N-P-K ratio with less emphasis on nitrogen. 

Nitrogen is an all-around fixer as its important for amino acids, which are a building block of plant proteins and enzymes. 

Good for root growth, but not directly responsible for more growth overall. 


Calcium doesn’t directly help roots grow better, but it does help them grow stronger. 

Much like calcium builds strong bones in people, it helps create more and stronger cell walls and membranes, resulting in an easier and more stable growth of roots.