A Guide To Hydroponic Cannabis Growing With Different Mediums

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Cannabis plant leaves looking green and healthy
December 22, 2020
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Hydroponic systems are all the rage among marijuana growers. Growing marijuana hydroponically entails cultivating the plants in a nutrient-enriched liquid with or without an inert medium. Put another way; it means growing without soil.

Growing plants using hydroponics is nothing new. It has been around for centuries, dating back to the Hanging Gardens of Babylon around 600 BC. From crude agricultural methods, it eventually evolved into an intricate art and science powered by advanced techniques. Now, you have a wide range of soilless media and systems at their disposal.

When it comes to growing marijuana, some growers prefer to use more standard, soil-based growing methods, however, hydroponics is the only way to grow for some cannabis cultivators.

In this article, we will tell you the available options – including their notable qualities. But, it does not end with the choices you make at the beginning. You also have to monitor and maintain the hydroponics system. If successful, you can have more control over the garden, resulting in exponential marijuana growth and yields.

We’ve already shown you how to make a stealthy hydroponic grow box but now let’s look a little bit more at the different aspect of hydroponics and why it may be a good option for growers to explore.

How do you Grow Marijuana Using Hydroponics?

Hydroponic growing is quite straightforward. Start by selecting a soilless medium and an appropriate hydroponic setup. Usually, a specific system will only be compatible with certain substrates. In some cases, you might not even need a growing medium. After planting and feeding the crops, as well as monitoring and maintaining the system come some of your most critical concerns. This method of growing marijuana entails feeding the root system directly.

At its core, hydroponics is all about coaxing the highest potential yields from marijuana plants. The amount of bud you harvest will be more than what you would get from any other growing technique. Not only do you have full control over the nutrients, but the uptake is also optimal as the roots are directly exposed to the nutrient solution. Furthermore, there is improved aeration at the root zone.

The optimal nutrient and oxygen intake results in faster, more vigorous growth and increased plant resilience. Ultimately, it leads to an earlier harvest period and more prolific, bigger, and more potent cannabis buds – even much more so than their soil-grown counterparts.

What are the Downsides of Using Hydroponics?

For one, hydro systems have an initial cost and setup. More than that, it tends to be more demanding and less forgiving than soil. In particular, you might have a hard time figuring out the correct nutrient formulas and dealing with root problems. For these reasons, it is more suited for those already familiar with cannabis growing. Finally, buds fed with liquid nutrients tend to have less complex aromas and flavors than those raised in soil.

What are the Different Hydroponic Media?

There are several types of hydroponic or soilless media, each with varying properties. But, they mainly serve the same functions, including:

  • Housing the sensitive roots while giving them enough space to grow and develop
  • Ensuring that the root zone has all the moisture and oxygen it needs
  • Acting as a channel for nutrient absorption
  • Offering structural support and keeping the plants upright
  • Anchoring the plants in place

The chosen growing medium will need certain qualities to perform these tasks successfully. You also want to make things as seamless as possible – while minimizing your environmental impact. In that regard, the chosen medium has to meet most – if not all – of the following traits:

  • Porous and aerating
  • Decent water retention properties
  • Balanced air to water ratio
  • Lightweight but not buoyant
  • Inert (or close to it)
  • Clean
  • Easy to prepare, use, and handle
  • Durable and reusable
  • Cost-effective
  • Sustainable

The following are some of the best hydroponic media you could use:

1. Coco Coir

Coco coir is an all-natural medium sourced from coconut husks. It comes in many forms, with tightly compressed bricks being among the most widely available. Before use, they need to be washed, rehydrated, and buffered to make them suitable for cannabis plants. Once finished, you would be left with loose, fibrous materials that look like soil.

Coco coir, being exceptionally porous, can provide an optimal blend of water retention, aeration, and drainage abilities. It ensures that the plants have all the moisture, nutrients, and oxygen they need to grow and thrive.

This substrate is a godsend to growers and to the environment, too. Aside from being easy to use and handle, it is also sterile and reusable. While being quite expensive, it is incredibly durable and lasts a long time, making it cost-effective. On top of that, coco coir is eco-friendly and highly sustainable, allowing you to grow with a clean conscience.

2. Perlite

Perlite is an amorphous volcanic glass made by mixing obsidian with water. Appearance-wise, it resembles popcorn – small, rounded, and whitish. You can use it as a standalone medium or combined with vermiculite at a 1:1 ratio. Before use, rinse it thoroughly to get rid of the dust particles.

Despite having a decent moisture content, perlite does not retain water well and may require more frequent irrigation. That is because it is lightweight and porous, promoting drainage and oxygenation at the roots. At the same time, it also prevents compaction and makes it easier for the nutrients to circulate.

Perlite, while on the cheaper side, is exceptionally durable and does not decay, making it reusable. On top of that, it is sterile and non-toxic, not posing any health and environmental dangers when thrown away. And although a non-renewable resource, the current reserves are expected to last a long time. But, there are concerns about its mining and production, which can be energy-intensive.

3. Vermiculite

Vermiculite, usually mixed with perlite in equal ratios, is another naturally occurring mineral. Made from compressed sheets of silicate materials, it comes in colors ranging from dark to golden brown and appearing like thin metallic flakes when dry. You would have to wash it thoroughly before using it to clear any dust particles, which can be an irritant.

Like a sponge, vermiculite works by absorbing and retaining moisture. In essence, it can make up for the poor water-holding capacity of perlite. It can help enhance aeration as well. On the flip side, it does not drain water well, making it prone to over-watering when used by itself.

Compared to perlite, vermiculite tends to be pricier and harder to come by. But, it is also sterile, non-toxic, and reusable. The downside is that it may disintegrate and break apart after a long period of use. And, there are concerns that it is being mined at an alarming rate.

4. Clay Pebbles

Clay pebbles or pellets are made by heating clay to high temperatures, causing it to expand and form bubbles, and finally taking the shape of small, brown spheres. Alternatively, it can also be called hydroton, expanded clay (exclay), hardened expanded clay (HEC), and lightweight expanded clay aggregate (LECA). At any rate, you would have to rinse and soak it before use.

Because of tiny air bubbles, clay pebbles are exceptionally porous and airy, which is why it has excellent drainage and promotes optimal oxygen intake. On the flip side, it does not hold moisture as well as other substrates. Another notable trait is that it is sturdy and quite dense. And being structurally sound, this substrate does not float away when irrigated, allowing it to anchor the plants in place.

Clay pellets, being in loose form, are a breeze to handle and work with – plus, it is sterile and reusable almost indefinitely. You just have to prep it properly before every growing cycle. It is also ecologically sustainable since it is derived from clay – an abundant and renewable resource.

5. Rockwool

Rockwool – also called mineral or stone wool – is made by spinning molten volcanic rock into thin fibers. It is available in various shapes and sizes, including cubes, blocks, slabs, and even loose forms. Before use, this medium is rinsed and conditioned to rid it of abrasive and irritating properties, making it viable for growing marijuana.

The permeable, wool-like texture of mineral wool gives it an ideal balance of drainage and water retention capacities. When damp, it holds an equal air to moisture ratio, ensuring that the roots are well-aerated and amply-hydrated. It also gets heavier when saturated, making it more stable. Such absorbency, though, can lead to mineral buildup and mold formation over time. Using a fresh nutrient solution every single time helps avoid this issue.

Rockwool is budget-friendly and highly efficient. It is also sterile and does not decompose, making it reusable. The sustainability of the material often depends on the manufacturer. Some, for example, use recycled materials and take extra effort to lower the operational footprint. Meanwhile, others might use stone, which may require large amounts of coal and energy to produce.

What are the Different Hydroponic Systems?

The five most popular ones are the wick system, deep water culture, nutrient film technique, drip system, and ebb & flow. Each has different mechanisms, requiring specific parts and a growing medium. Some are cheap to install and maintain, while others can be pricey and labor-intensive.

Furthermore, a hydroponic system can be active or passive. ‘Active’ means that it uses a pump to transport the nutrients from the reservoir – a tank containing the nutrient solution – to the plants. On the other hand, ‘passive’ systems rely on a wick to draw up and deliver the minerals.

Aside from this, the hydroponic arrangement can also be recovery or non-recovery. In ‘recovery’ setups, the nutrient solution is recirculated or reused in the system. In contrast, ‘non-recovery’ simply means that the liquid is applied directly to the substrate and eventually disappears.

1. Wick System

  • Recommended Growing Media: Coco coir, perlite, and vermiculite
  • Type: Passive and non-recovery

In this system, a ‘wick’ – typically a porous material like nylon gauze – is placed at the plants’ bottom to connect the pots to the reservoir. Through capillary action, the wick absorbs the nutrient solution and delivers it to the root zone. And as the roots soak up the nutrient-rich liquid, more is drawn up from the reservoir.

The wick system is among the simplest of its kind. On top of that, it is inexpensive and easy to set up, making it ideal for beginners. Unfortunately, it may not supply enough water to saturate the medium. Likewise, it may not deliver nutrients as efficiently as other systems. For these reasons, it is better suited for smaller plants or growers with limited space.

2. Deep Water Culture (DWC)

  • Recommended Growing Media: Hydroton and rockwool
  • Type: Active and recovery

In a DWC setup, the plants are placed on a floating platform, keeping them suspended above the nutrient solution. Meanwhile, the root system is left dangling and completely submerged. To keep the roots well-oxygenated, an air stone at the bottom of the reservoir sends oxygen bubbles upward. You can also control the amount of air. All you have to do is adjust the settings of the air pump – which is found outside the reservoir and connects to the airstone via a tube.

A DWC system is the simplest type of active hydroponics. Like the wick system, it is also cheap and straightforward to set up while also being low-maintenance. Just keep in mind that it may not be suitable for large marijuana varieties and those with longer life cycles.

3. Nutrient Film Technique (NFT)

  • Recommended Growing Media: Clay pellets
  • Type: Active and recovery

NFT is among the more complex hydroponic systems. Primarily, it consists of three core parts:

  • A grow tray holds the plants in a floating platform with roots hanging down and exposed to the nutrient solution
  • The reservoir, located directly below the tray, holds the nutrient solution, a pump, and air stones
  • A hollow tube called ‘channel’ at the bottom of the grow tray that extends down the reservoir

The pump in the reservoir continuously dispenses the nutrient solution onto the grow tray – which is slightly angled downwards in the direction of the channel. This design forces the liquid to drain back to the reservoir, feeding the root systems as it travels down.

The NFT requires little to no growing medium – just a bit of clay pebbles will do. And since the nutrient solution recirculates automatically, there is no need to install a timer. Such an arrangement also reduces water wastage. Take note, though, that the NFT is not suitable for extra large and heavy plants.

4. Drip System

  • Recommended Growing Media: Coco coir, vermiculite, expanded clay, and mineral wool
  • Type: Active and recovery (but non-recovery ones are common in commercial setups)

A drip system is among the most popular hydroponic setups. Like the NFT, it has a reservoir system that continuously feeds nutrients to the plants. Unlike the NFT, though, the root system is not fully exposed and laid out across the grow tray. Instead, they are housed in a standard hydro substrate. Mainly, the pump carries the nutrient solution up to the drip manifold – a series of drip lines and emitters above the grow tray – which delivers the liquid directly to the medium.

The mechanism behind a drip system is simple – but highly effective. You can also automate the whole process using a timer, giving you more control over the feeding schedule. Do keep in mind that it is an advanced system, and setting it up can be laborious. Hence, it may be more suitable for more seasoned growers.

5. Ebb & Flow

  • Recommended Growing Media: Clay pebbles and rockwool
  • Type: Active and recovery

The ebb & flow system – also called the flood and drain – primarily involve a grow tray and a reservoir.

In this setup, the plants alternate between wet and dry cycles. The roots absorb nutrients and oxygen when the reservoir system floods the growing medium with the nutrient solution at set amounts and intervals. Afterward, the solution drains out of the tray, returning to the reservoir.

This system is relatively easy to assemble, but you need some working knowledge to operate it properly. It does come with a timer that automates the task of ‘flooding’ periodically, which reduces the risk of drying out the roots. The amount of nutrient solution also has to correspond with the nutrient and moisture needs of the plants.

What Hydroponic Nutrients Should You Use?

With professional blends designed explicitly for hydroponics, there is no need to experiment with nutrient mixtures and ratios. This may lead to you misfeeding your plants whereas professional blends already have the required nutrients for your marijuana plants to grow. Some of the go-to brands of veteran cannabis cultivators include General Hydroponics and Botanicare.

Make sure to familiarize yourself with the nutrient requirements of cannabis plants across the different stages of growth. You need to know the ideal NPK ratios – which expresses the amount of nitrogen, phosphorus, and potassium present in the nutrient mix. During the vegetative phase, for instance, plants require high amounts of nitrogen. Once they start flowering, phosphorus is more needed than nitrogen.

The next step is to prepare the nutrient solution using the preferred fertilizer. Read the product label as it should include the recommended strength and feeding schedule. For the base, remember to use only good-quality water that is free from chemicals and other impurities. Before feeding, ensure that the nutrient solution sits at the right pH, EC, and temperature levels.

How Do You Monitor and Maintain the Hydroponic System?

To monitor the hydroponic setup, you have to ensure that the pH, EC, and temperature are at ideal levels. All you need is a digital multimeter, which can easily measure the pH, EC, and temperature of the nutrient solution. Generally, the pH should fall between pH 5.5 to 6.5. The temperature should also be slightly warm or about 72°F (22°C).

The optimal EC – the electrical conductivity or overall nutrient content – varies immensely across the growth stages, ranging from 400 to 1600 μS/cm. Afterward, adjust accordingly. If not, the roots struggle to absorb the nutrients present in the solution. To make matters worse, they would be more susceptible to diseases, too.

You want to prevent the buildup of salts, bacteria, and fungi. To do that, you should change the nutrient solution every two to three weeks. While at it, clean and sterilize the reservoir system as well.

A major benefit to growing marijuana in hydroponics is that it is a far cleaner process than planting in soil. You do not have to worry about mounds of dirt on the floor, for one. Also, the use of sterile and inorganic substrates (only coco coir is organic) means that you are less likely to attract pests and pathogens.

For best results, maintain the general cleanliness of the growing area. You can do this by sweeping, mopping up any spills, discarding any plant debris, and sanitizing the surfaces and the rest of the room.

Go Ahead, Grow Marijuana with Hydroponics

Growing marijuana in a hydroponics system is the best way to boost the growth rate. Compared to soil mediums, it is cleaner and easier to maintain. However, you will have to decide on which system to use. For simplicity, you could opt for commercial solutions using either a deep water culture or a drip system. You could make them yourself, or purchase one set that comes with everything needed – all the equipment and accessories. Whichever you decide, one thing you can be sure of is an explosive growth rate.

All you need to do now is buy yourself some high-quality marijuana seeds from Homegrown Cannabis Co. and you are ready to start your growing journey. If you need any more information on hydroponics head on over to our new Homegrown Cannabis Co. forum.