Passive Hydroponics: The Easy Way to Grow Plants Indoors

One of the first hydroponic setups I tried was a passive system, and I couldn’t believe how simple it was to grow plants with it! Nowadays, I still use this method for some of my plants.

Passive hydroponics is a soilless method of plant cultivation using a non-circulating, nutrient-rich water solution. It doesn’t require electrical components and transfers nutrients from the water to the plant’s roots, through direct submersion of roots (Kratky method) or by using a wick, mesh, or foam.

Growing your own plants indoors can be a fun and rewarding experience. With passive hydroponics, you can do it with minimal effort and cost! Not only is this method simple to set up, but it also keeps the plant’s roots healthy and well-nourished. Plus, if you’re short on space or time, passive hydroponics might just be the perfect solution for you.

Keep reading to learn more about how passive hydroponics works and how you can get started today!

What is passive hydroponics?

Hydroponics Is a method of growing plants without soil, using a nutrient-rich water solution instead. But what is passive hydroponic then?

Passive hydroponics is a type of hydroponic system that doesn’t require any electricity, pumps, or other fancy equipment which you often see in traditional or “active hydroponic”. Instead, it uses the natural process of wicking to transfer water and nutrients to the plant’s roots.

This means that it’s super easy to set up and maintain, and it’s perfect for beginners who want to try their hand at indoor gardening.

In a passive hydroponic system, plants are grown in containers filled with a growing medium, such as perlite, vermiculite, or coconut coir. The growing medium provides support for the roots and helps to maintain the right level of moisture.

The nutrient-rich water is then added to the container, where the plant is consuming it, either by direct submersion of the roots (Kratky method) or by using a wick, mesh, or foam to transfer the water from a reservoir to the growing medium. This provides the plants with all the water and nutrients they need to thrive, without the mess and hassle of traditional soil-based gardening.

How it differs from traditional hydroponics

But what exactly makes passive hydroponics different from traditional hydroponics? In a nutshell, passive hydroponics systems don’t rely on pumps or electricity to circulate nutrient-rich water throughout the growing medium. Instead, the water sits still, while the plant roots absorb the nutrients they need directly from the water or from a wick that draws the water to the roots.

This lack of electricity also means that passive hydroponic systems can be more affordable and easier to set up than traditional hydroponics systems. Plus, without the need for complex equipment, passive hydroponics is a great choice for those who are new to indoor gardening and want to dip their toes into hydroponics without investing a lot of money or time upfront.

Benefits of Passive Hydroponics

1. Low maintenance: Passive hydroponics requires little maintenance, with less need for monitoring and adjusting nutrient levels and water flow compared to traditional hydroponics. Making it an ideal choice for busy gardeners or those who are new to hydroponics.
2. Cost-effective: Compared to traditional hydroponics, passive systems are generally less expensive to set up and operate, as they don’t require pumps or electricity.
3. Water efficiency: Passive hydroponics can be very water-efficient, as the nutrient solution is usually contained in a closed system, meaning there is little to no water loss through evaporation or runoff.
4. Healthy plant growth: Because the plants receive a constant supply of nutrients, they can grow quickly and healthily, without the risk of over- or under-fertilization.
5. Space: One of the main benefits of passive hydroponics is that it requires less space than traditional hydroponics systems. This is because it doesn’t need pumps, tubing, and other equipment that take up a lot of space. Instead, a passive system uses a simple design with fewer components, making it easier to set up in small spaces like apartments or balconies.
6. Versatile: Passive hydroponics can be used to grow a wide variety of plants, from herbs and leafy greens to certain fruiting plants, making it a flexible and adaptable growing method.

Best plants to grow using passive hydroponics

If you’re interested in trying passive hydroponics, it’s important to know which plants will thrive in this type of system. Luckily, there are plenty of options to choose from! Some of the best plants for passive hydroponics include:

• Herbs
• Leafy Greens

and fruiting plants like:

• Tomatoes
• Peppers

Plants with smaller root systems tend to thrive better in a passive hydroponic system because they require smaller containers and use less water. However, it’s possible to grow all kinds of plants in a passive hydroponic system, as long as you calculate the appropriate container size needed for the specific plant.

How to set up a passive hydroponics system

Now the fun part – setting up your passive hydroponic system! As mentioned earlier there are different ways to set up a passive hydroponic system. one of the easiest methods is the one where you submerge the roots directly in the nutrient solution, this method is also called Krakty.

The Kratky passive hydroponic method

The Kratky method is a type of passive hydroponic system that was developed by Dr. Bernard A. Kratky of the University of Hawaii. This method allows plants to grow in a stationary, non-circulating nutrient solution without the need for pumps, electricity, or timers.

In the Kratky method, plants are grown in a container filled with an inert growing medium such as clay pebbles. The container is then filled with a nutrient solution up to a certain level, which is determined by the height of the growing medium.

The plant roots are submerged in the nutrient solution and as the plant uses up the solution, the water level gradually decreases.

As the water level drops, the plant roots grow longer and begin to create oxygen roots above the waterline. These oxygen roots are important for the plant’s survival as they take in oxygen from the air and release carbon dioxide into the atmosphere. This process also helps to keep the nutrient solution oxygenated, which is essential for healthy plant growth

The Kratky method is a set-and-forget system, once it is set up the nutrient solution should last for the entire plant’s growing cycle. This makes the Kratky method a great option for beginning gardeners.

But what If you have plants with a longer growing cycle? don’t worry – I will cover what to do in more detail later on in the article.

Equipment needed for Kratky passive hydroponic

Before you start setting up your passive hydroponic system, you must ensure you have all the necessary equipment. Here’s a list of what you’ll need:

1. Container: You will need a container to hold the nutrient solution and growing medium. This can be any type of container, such as a plastic tub, bucket, or even a recycled container, as long as it is large enough to accommodate your plants.
   
2. Lid: A lid is needed to cover the container and prevent evaporation of the nutrient solution. The lid also helps to keep the growing environment clean and free from debris.
   
3. Net pots: Net pots are used to hold the plants and their growing medium in place. They allow the plant roots to grow through the bottom and into the nutrient solution.
   
4. Growing medium: In a Kratky system, an inert growing medium is used to support the plant and its roots. Clay pebbles are a popular choice as they are lightweight, provide good aeration and drainage, and are reusable.
   
5. Hydroponic fertilizer: Since the plants are grown in a nutrient solution, it is important to provide them with the right balance of nutrients for healthy growth. A hydroponic fertilizer designed for the specific plant you are growing will provide the necessary nutrients. I’m a big fan of Terra Aquatica’s (general hydroponics) 3-part solution.
   
6. Additional supplies: A pH and EC meter can be used to measure the pH level and electrical conductivity of the nutrient solution. Adjusting the pH level and monitoring the EC can help ensure that the plants are receiving the proper nutrients. A pH-down solution may also be needed to lower the pH level if it is too high. I like this Ph and EC meter and for pH-down you can use this.

A step-by-step guide to building a passive hydroponics system

1. Choose a container: The first step in building a Kratky system is to choose a container that is suitable for the plants you wish to grow. It should be large enough to accommodate the plant’s root system and provide enough space for the growing medium. I have chosen an old jar glass container
   
2. Cut holes in the lid: Once you have selected the container, you will need to cut holes in the lid for the net pots. Net pots are plastic containers that hold the plants in place and allow the roots to grow through the bottom into the nutrient solution. To cut the holes, use a drill with a hole saw or a sharp knife if its plastic.
   
   
3. Prepare the net pots: Once the holes have been cut, place the net pots into the holes. The bottom of the net pots should be flush with the top of the lid. You can use a hot glue gun to secure them in place.
   
4. Add the growing medium: Add the growing medium into the net pots. I use clay pebbles as they provide excellent drainage and aeration for the roots. But if you have started your seedlings in Rockwool or another medium it’s also possible to use that.
   
5. Mix the nutrient solution: Mix the hydroponic fertilizer with water according to the instructions on the package. Be sure to use a pH and EC meter to check the pH and nutrient levels of the solution. your pH should be 6-6.5, you can check your required EC level for your plants here
   
6. Fill the container: Fill the container with the nutrient solution up to a level that is just below the bottom of the net pots. The water level should not touch the bottom of the net pots, as this can cause the roots to rot. Interested in learning more about how to prevent root rot, then I have this article for you.
   
7. Plant the seedlings: Carefully plant the seedlings into the net pots. Make sure the roots are fully covered by the growing medium.
   
   
8. Place the lid on the container: Place the lid on the container, making sure that the net pots are securely in place.
   
9. Monitor the water level: Over time, the water level in the container will decrease as the plants use up the nutrient solution. This will create an air gap between the water and the lid, which will allow the roots to grow oxygen roots.

That’s it! Now you have a fully functioning hydroponic system. But what if you have a plant with a longer growing cycle and your plant has almost used up the nutrient solution?

Refilling the Kratky Growing Method for Longer-Growing Cycle Plants

Growing longer-cycle plants in a Kratky system can be challenging as they tend to consume more nutrient solution.

However, with the right approach, it is still possible to succeed. In cases where the container is not big enough, or the nutrient solution runs low, you can refill the Kratky system with a new solution.

However, this process must be done with the most care, as an incorrect approach can harm the plants.

Here’s how to refill your Kratky system safely:

Check the Nutrient Level

If there is more than half of the original solution remaining, and the roots are not touching the water, refill with clean water. If less than half the solution remains, or you’ve previously refilled with regular water, it’s time to refill with a new nutrient solution.

Refill with a New Nutrient Solution Mix

It’s crucial to avoid mixing new solution with the old one, so wait until there’s as little old solution as possible in the container. Mix a fresh solution in a separate container according to the manufacturer’s instructions. Use a pH and EC meter to measure the levels, and then carefully pour the new solution into the Kratky container without disturbing the roots.

Don’t Fill All the Way Up!

To prevent root rot and ensure the roots have enough oxygen, leave a 1-inch gap between the solution and the net pot. This step is crucial, and failure to follow it can lead to root rot and in the end plant death.

By following these simple steps, you can successfully refill your Kratky system with a new mix of nutrient solutions. Just remember to be careful and not overfill the container.

Conclusion

Passive hydroponics is a simple and cost-effective method of growing plants without soil, using a nutrient-rich water solution instead.

Unlike traditional hydroponic systems, it doesn’t require pumps or electricity, making it a great choice for beginners or those on a budget. This method offers many benefits, including low maintenance, cost-effectiveness, water efficiency, healthy plant growth, space-saving, and versatility.

Plants with smaller root systems like herbs, leafy greens, tomatoes, and peppers are best suited for passive hydroponics. Setting up a passive hydroponic system is easy, with the Kratky method being one of the easiest and most popular methods.

If you’re interested in indoor gardening, passive hydroponics is a fun and rewarding way to grow plants without the hassle of traditional soil-based gardening.

Happy Growing! 🙂

FAQ

Q: Can I use passive hydroponics to grow other types of plants?

A: Yes, passive hydroponics can be used to grow a variety of plants. However, it is best suited for smaller root systems like herbs, leafy greens, tomatoes, and peppers.

Q: How often do I need to change the nutrient solution?

A: It depends on the type of plants you are growing. Some require more frequent changes, while others can go many weeks without changing the nutrient solution. If using the Kratky method, it is best to check the water levels every few days and refill when needed.

Q: How do I know if my plant’s roots are getting enough oxygen?

A: The easiest way to tell is by looking at the top of your container for an air gap between the water and the Growing medium. This shows that there’s enough oxygen in the system for your plants’ roots to thrive. You can also use a pH and EC meter to double-check that everything is working correctly.

Q: What should I do if my plants are not growing?

A: First, make sure there is enough light, nutrients, and oxygen in the system. Second, check the pH and EC levels to ensure they are within the proper ranges for your plant type. Finally, adjust the water level if needed to provide adequate aeration and nutrient uptake. If you’re still having trouble, consider using a different nutrient solution or consulting an expert for additional help.

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