Organic Hydroponic Guide

Hydroponics is, for many, a branch of organic gardening. True, if you think about organic gardening, you will have pictures in your mind of green farms, permaculture beds, composting, even food forests.

The image of a hydroponic garden does not match that of organic gardening. But don’t judge a book by its cover…

So, Can you grow organic hydroponics?

Yes, you can, hydroponics has developed as a form of organic gardening; it does not need to be, but most hydroponic gardeners grow plants organically. You can easily run your hydroponic garden organically; you will only need to use organic fertilizers and pest control. 

Have you come to hydroponics because you want organic food or decorative plants? Then stay with us and you will find out how you can do it.

In fact, you will find out that growing plants organically with hydroponics is simpler than in the soil.

Is Hydroponics an Organic Form of Gardening?

Is Hydroponics an Organic Form of Gardening_

Hydroponics can be organic and in most cases it is. However, you can use chemical (synthetic) fertilisers and even pest control products in your hydroponic garden, and in this case, of course, your plants will not be organic.

Having said this, most hydroponic gardeners are organic gardeners and most hydroponic products are organic products. This is because the mindset of most hydroponic gardeners is also organic.

The choice is yours, but reading on, you will find out how easy it is to run your hydroponic garden according to organic methods, and I am sure you’ll be convinced that this is the way forward…

Hydroponics and Soil

Hydroponics and Soil

Hydroponic gardening does not use soil. But soil is central to organic gardening. In fact, organic gardening derives from Humous Farming, a revolutionary movement born before the Second World War in Europe with three principles:

  • Feed the soil, not the plants.
  • Use crop rotation.
  • Develop an alternative distribution line.

Feeding the soil, rather than plants, then became a core concept of organic gardening. But this is hard to do when instead of soil, you use a nutrient solution and maybe a growing medium, isn’t it?

Nevertheless, as long as you only use organic products in your garden, your plants will be organic.

Actually, I am lying; to be precise, you should also use organic seedlings or seeds…

But these are all things you can easily do with hydroponic gardening.

The difference is mainly a limitation: organic gardening is developing into forms of regenerating the land (even turning deserts into fertile land), with permaculture and regenerative agriculture, while hydroponics is not very useful in that direction.

Hydroponics’ Contribution to the Green Revolution

Hydroponics’ Contribution to the Green Revolution

But this does not mean that hydroponics does not have a role to play in the organic and green revolution – on the contrary…

Hydroponics is making organic gardening available even in urban areas, and even inside your home.

If you have a small plot of land next to an incinerator, your soil will be polluted, and your food will not be organic.

But with hydroponics, you can grow organic food even in inner cities; actually, maybe the future will have libraries with tomatoes and lettuce growing in them, organically and thanks to hydroponics.

Hydroponics cannot regenerate the soil, but it can regenerate urban settings.

So, its potential in the green revolution is huge. Also because it is making home made food much more accessible to all, even if you don’t have a plot of land…

What Does It Mean When a Plant Is Organic?

What Does It Mean When a Plant Is Organic_

First, let’s start by saying what “organic” means; in fact, it can stand for two things:

  • Plants that you grow organically and you know they are.
  • Products that have the “organic” seal on them.

In the second case, you will need to have your products certified; this varies from country to country, but be assured that hydroponic gardening can be certified as organic.

But of course, you will want the label on your products only if you intend to market them. For most people, it will suffice to know that what you put on your table is free from synthetic chemicals.

How Do Hydroponic Plants Absorb Synthetic Chemicals?

Plants absorb chemicals through the roots, but also through the aerial part (trunk, stems, leaves, flowers and fruits too).

So, to make your plants as organic as possible, you will need to avoid that your plants gets into contact with any synthetic chemical product.

This has two sides to it; while it is easier to control the absorption of synthetic chemicals through the roots with hydroponics, it is harder to do it through the leaves.

Basically, it is hard to control the air quality. That’s the same for soil organic gardening, but if you want an organic farm, you will choose a place in the countryside.

This is not something that someone who wants to grow a few plants at home can do… You won’t move to a remote place in Nevada to have a few strawberries and tomatoes on your dinner table!

So, the quality of your veggies and fruit will always depend on the air they breathe.

But when it comes to root absorption, with hydroponics you have a major advantage: as long as your water is not polluted, you can have a head start and all things become easy.

Organic Hydroponic Gardening and Herbicides

Organic Hydroponic Guide

Let’s start with a problem solved: with hydroponics you will not need herbicides. This already makes it easier for you to run your garden organically.

One of the main pollutants in gardening is the use of herbicides. It actually sets off a horrible cycle; the herbicide not only damages the soil and pollutes the plants, they often cause infestations of plants that are resistant to it.

But with hydroponics, as there is no soil, you will not need to use herbicides.

Organic Hydroponics and Algae Control

There are no blades of grass bothering you with hydroponic gardening, bit your tanks may develop algae. Algae are the weed of hydroponic gardening.Fortunately, they are easier to manage than actual weed though…

  • Make sure your tanks are covered in dark and non translucent material. This includes your reservoir and your grow tanks. The absence of light will make algae growth more difficult.
  • Wash and sterilise your growing medium; do this before you use it and at any change of crops. This will not only help with algae growth, but also with bacteria.
  • Keep an eye on tanks, pipes and hoses for algae growth.
  • Clean your tanks, pipes and hoses when you change crops; the best time to get rid of algae is when your garden is not operating, so, between crops.

Now, keep in mind that you will have algae in your garden, but a few algae are no trouble at all. That green layer, or patina, on the sides of tanks is more than fine.

The problem starts when they overgrow, as they may clog your system and, in serious cases, compete for food with your plants.

Some methods (drip system and aeroponics) are less susceptible to algae growth than others, which use bigger flows of water or even stagnant water (ebb and flow and deep water culture).

The good news from an organic perspective is that you cannot use weed killers in a hydroponic garden; they would kill your plants as well.

Organic Hydroponic Feeding

Organic Hydroponic Feeding

The biggest absorption of synthetic chemicals in plants occurs through the roots, through feeding and fertilizing. This is where you can have a big impact. There are two ways you can go about it:

  • Buy an organic hydroponic nutrient mix (fertilizer).
  • Make your own organic nutrient mix (fertilizer).

The first is the easiest way. That’s what most small scale hydroponic gardeners do. It is easily available, cheap and very common indeed.

There are generic fertilizers as well as those for groups of plants (flowering, leaf vegetables, fruiting vegetables etc.) and even for specific plants. The choice is very wide and this will sort out all your problems.

The second choice is maybe for those who want to “go the full way” along the self sufficiency path or for big professional gardens.

Make Your Own Organic Hydroponic Fertilizer

Make Your Own Organic Hydroponic Fertilizer

There are many ways of making your own organic fertilizer for your hydroponic garden. Quite a few of these are actually quite complex. But let’s look at two that can give you an idea…

Mix The Nutrients Yourself

Mix the Nutrients Yourself

If you have a large hydroponic garden it is more convenient to get the organically sourced nutrients and then mix them yourself instead of buying a new ready made mix for each group or type of plants.

Please remember that there are generic fertilizers, so, don’t think that if you have a small garden you need to change mix every time. You may, however, want different fertilizers for groups of plants.

If you want a specific mix for a particular plant, then you will have to know exactly which concentrations of the different nutrients your plant requires.

A Simple Organic Fertilizer For Hydroponics

A Simple Organic Fertilizer for Hydroponics

If you want to make your own organic fertilizer for your hydroponic garden and you don’t have a degree in chemistry, there’s a simple way.

You will need:

  • Worm castings
  • Kelp
  • A lemon
  • Water
  • A mesh bag with a very thin net. This needs to be thin enough to strain the castings without allowing the droppings themselves to end up in the water. A 1 mm mesh is ideal.

If you have a worm farm, you can even use your own worm castings. But let’s see how you can do it:

  • Put kelp in a bottle of water.
  • Leave the kelp in the water till the water turns light green. This can take a few days.
  • Fill a container with 5 gallons of water. A big bucket will do.
  • Squeeze a few drops of lemon in the water. This will correct the hardness of the water.
  • Put the worm castings in the mesh bag.
  • Put the bag in the water.
  • Squeeze the bag. If you roll it up, this will be easier to do. Squeeze it so that the water becomes brown but no solid parts of the castings go into the water.
  • Add 20 cl of the kelp macerate.
  • Mix well.

As you can see, this is fully organic and fairly easy to prepare, but it won’t look great of your hydroponic garden is decorative.

Pest Control for an Organic Hydroponic Garden

Pesticides are major causes of pollution and if you use synthetic pesticides, your plants cannot be called organic. Fortunately, hydroponic plants are rarely attacked by pests. This can already make you breathe with relief…

Plants grown with “industrially” are far more liable to pest infestations than plants that grow in a well managed ecosystem, and also much more than plants grown hydroponically. This is a statistical fact backed up by data and research.

Still, you may have the odd problem even with hydroponic plants; these are more likely of you grow them in a greenhouse and if your garden is a monoculture.

Fortunately, organic gardeners have come up with so many viable alternatives to synthetic pesticides that, to be honest, it’s hard to see why anyone would use chemicals nowadays. Let’s see some…

Planting As Pest Control

Planting as Pest Control

Using planting to control pests is one of the main developments of organic gardening, and it can be done with hydroponics as well.

Of course, there will be adaptations to make, as hydroponics is not a garden with permanent planting in most cases and it is not in an open field…Still, some key concepts can be applied to hydroponics, and they are very useful to deter pests.

  • Avoid monoculture; if your garden is large and it only has one type or species of plants, it will attract pests from afar and they will spread quickly from specimen to specimen.
  • Plant herbs; most herbs, like mint, citronella, lavender, rosemary and chives repel pests. All you need is their scent in your hydroponic garden and pests will keep at a distance. So, plant them among your veggies and decorative flowers to have a healthy and pest free garden. Also note that lavender will keep pests away but attract lots of pollinators.
  • Plant marigolds and petunias; marigold in particular is loathsome to almost all insects. Petunias too get many pests packing. So, adding a touch of beauty to your garden can also mean having a healthier hydroponic garden.

Ventilation As Pest And Disease Control

One of the main problems of indoor gardening is the lack of fresh air and ventilation. Very often (though not necessarily), hydroponic gardens are indoors. Do make sure that you ventilate it properly because:

  • Ventilation reduces the risk of bacterial infections and similar. A warm, humid and stuffy place is the best breeding ground for pathogens that carry disease.
  • Ventilation keeps your plants strong; stuffy air will weaken your plants, and this will in turn make them more vulnerable to pests. Not only, having a weakened immune system, they will not stand any infestation as well.
  • Regular ventilation allows “good bugs” to find your plants. The predators of pests (like ladybugs etc.) need to find them and then eat them; if you keep the windows closed, you will lock them out when you most need them.

“Good Bugs” As Pest Control

Ok, in Nature there are no bad bugs and good bugs, but in gardening, a good bug is an insect (or predator, including arachnids) that preys on an infesting one.

So, we can use them to control the population of damaging pests, and this has been done for many decades now.

It is easier to do it if you have a large plot of land, with shady areas, even water etc., but you can still encourage them into a small greenhouse if you want a balanced ecosystem for your hydroponic garden.

Beetles, ladybirds and similar insects are excellent “good bugs”. You can do two things to have them working for you as your pest control team:

  • Literally buy them, or in any case bring them to your garden.
  • Encourage them with a welcoming environment.

Encourage Beetles And Ladybugs In Your Hydroponic Garden

It is easier and there are more ways to encourage them with soil gardening, but you can do a few things even in a greenhouse:

  • Make a pile of decomposing logs; beetles will use it as a “nursery” to lay their eggs and reproduce. You will be amazed how many you will get in a matter of months or even weeks.
  • Place clusters of cut bamboo reeds around your greenhouse. Place them at least 3 ft (1 meter) high, and in warm, sheltered and sunny place. Wrap some straw around your bundle and ladybirds and other small beetles will use them as shelter.

Garlic And Chili As Pest Control

Garlic and Chili as Pest Control

Did you know that only Humans naturally eat chili peppers? Pests hate chili and garlic and you can use these very easily as pest control.

Yet again, these small creatures are very sensitive to the smell of these plants, and, the nice thing is, you can make them into sprays.

Spraying plants with garlic or garlic and chili water is excellent against pests.

How can you make it though? There are different recipes, but one that combines garlic (enough to keep most pests away), chili and an agent that makes the spray stick to your plants is this:

  • Put a few cloves of garlic and a few chili peppers in a bottle of water.
  • Seal it and leave the garlic and leave it for 2 days.
  • Melt some natural soap in a bowl of water. Half a bar of soap per liter is plenty.
  • Mix the soapy water with the garlic and chili water in a spray bottle.
  • Shake well and spray your plants abundantly.

It is true that your plants will smell of garlic for a few hours, but then the smell will drop under our ability to perceive it, but not that of bugs…

In fact, they will smell it for about two weeks, or till the next rain of outdoors, and keep away.

This is so cheap and easy that you can literally spray your plants every fortnight and be quite safe against pests.

Neem Oil As Pest Control

Neem oil is becoming a favorite organic treatment all over the world, against pests, bacteria and fungi. It is readily available, fully organic and it cannot harm your plants.

It can also be used when the infestation or disease has become worrying, by which I mean it is at an advanced stage. You can use pure neem oil on a cloth and wipe your plants or, if you prefer a quicker and easier way:

  • Melt half a bar to a bar of natural soap Ina liter of water.
  • Allow it to cool.
  • Add a tablespoon of pure organic neem oil.
  • Pour it into a spray bottle and spray your plants abundantly.
  • Repeat every 10 days.

The Key Areas of Organic Hydroponic Gardening

Now, to recap, let us look at the four main areas of expertise that you need to develop to make sure that your hydroponic garden is both organic and successful:

  • Plant organic seeds or seedlings; a plant is only organically it was born as that.
  • There is no weeding, but control algae growth; you can easily do this by mechanical and fully organic means. No need for chemicals at all.
  • Always use organic nutrients, whether you make the fertilizer yourself or you buy it, make sure there are no synthetic chemicals in it.
  • Use organic pest control methods and treatments for disease. Here, the world’s your oyster as organic gardeners have developed a huge range of alternatives to pesticides. Keep in mind that plants can stand a small population of pests on them. It’s all a matter of quantity.

Is Organic Hydroponics Feasible?

Is Organic Hydroponics Feasible_

On the whole, it is fairly easy to grow your hydroponic garden organically. Because hydroponic plants are healthier, stronger and more pest free than soil plants, it is very easy to keep them strong and happy with simple remedies.

What’s more, there is no weeding to do, and this is already a simple way of avoiding the temptation to use dangerous synthetic chemicals.

Finally, you can feed your plants organically with no difficulty at all; the simplest way is to buy an organic nutrient mix if you have a small garden.

Why Organic Hydroponics?

In the end, it all boils down to a question: why did you want to grow your veggies and plants yourself?

Surely there is some satisfaction in eating carrots and peppers you have grown yourself, but most people also do it because they want healthy and organic food.

Hydroponics has always gone hand in hand with organic gardening, it is easy to run it organically and it would be a bit counterintuitive to use it to grow plants that are full of synthetic chemicals, what do you recon?

Adriano Bulla

Written By

Adriano Bulla

After many years as an academic in London, Adriano Bulla became a writer, publishing books like A History of Gardening, Organic Gardening and Elements of Garden Design; he then decided to become a gardener, following his childhood dream, and has been following his dream writing and gardening professionally in Southern Europe, where he has specialized in new and innovative organic gardening fields and techniques, like permaculture, regenerative agriculture, food forests and hydroponics.

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  1. Thanks for your post. I am putting together a 30’x18′ greenhouse to grow greens. I have built 2 of 3 kratkey style beds. My concern is how to develope organic nutrients without making a sollution of nasty water. So, thanks for your insights.

  2. Thank you for all this good information. But your fertilizer recipe says to use 20 cl of kelp macerate. What does cl stand for?

    1. Marjorie Fetchik Margie Fetchik says:

      cl is a written abbreviation for centiliter