Soilless Culture: How Growing Cannabis in a Hydroponic Substrate Increases Yields

For many, when we think of commercial cultivation, we imagine large fields where seeds are planted in the soil and watered by rain or large sprinkler systems. If a farmer is raising livestock such as cows or sheep on their land, it’s referred to as animal husbandry. However, if a farmer cultivates their land to grow herbs and vegetables, it’s referred to as horticulture. The term horticulture is Latin for, “gardening as a way of life,” and is often referred to as the science of cultivating garden-type herbs, fruits, and vegetables.

Soilless culture, or hydroponics, has been an increasingly popular cultivation method as it does not require field soil. Hydroponics facilitate the gardening and cultivation of food where there is little or no access to a nutrient-rich soil medium. This has allowed humans to cultivate plants for food in the desert, in the ocean, and in space.

Let’s take a closer look at soilless cultivation and hydroponic substrates. And then we’ll take a look at how a hydroponic substrate such as coco coir encourages healthier plant growth resulting in higher yields.

What Is Soilless Culture? (Hydroponics)

The easiest and most widely accepted explanation of hydroponics surrounds the practice of cultivating plants in a soilless medium while providing the plants with the four essentials they need to thrive: air, light, water, and nutrients. And of course, providing an environment with enough space for the roots and stems to grow, along with hospitable temperatures.

Soilless Culture
Hydroponics has allowed humans to grow crops in environments that otherwise would have not been feasible. With a properly balanced nutrient solution, plants can thrive without soil.

Geographical locations covered in field soil (dirt) provide access to a substrate for the world’s naturally thriving plant life. It retains water, provides nutrients to plant roots, and offers structural support for the plant’s primary stem and root system. However, dirt or a soil substrate is not required for plants to thrive. In fact, dependency on a soil substrate carries several disadvantages, including:

  1. Earth’s soil is slowly being depleted of nutrients in many places around the world. As we continue to commercially cultivate the soil, it’s important for us to use agricultural best practices to maintain a healthy soil-nutrient balance without the excessive use of fertilizers.
  2. Soil type and quality vary from region to region. While many farmers in the United States have access to fertile soil, there are locations around the world that do not have the topsoil for commercial agriculture.
  3. Humans need soilless culture solutions for exploration. Whether we build habitats on the South Pole, in the ocean, on the moon, or onboard an interplanetary rocket to Mars – transporting soil to these locations is not feasible.

A hydroponic system can mitigate most of the issues that arise from soil-based horticulture. Soilless grow rooms can greatly reduce your cannabis plant’s exposure to pests, mold, and fungi while providing essential nutrients such as nitrogen, potassium, and phosphorus.

Common Types of Soilless Culture Techniques

With the exception of the legendary hanging gardens of Babylon, hydroponics has come a long way. And with each soilless culture innovation, we’ve learned how to grow fruits and vegetables with increasing efficiency and skill. There are six primary hydroponic methods (depending on who you ask) and each has its own advantages and disadvantages.

Here is a very brief reference to the six main branches of hydroponics:

#1. Deep Water Culture (DWC)

Water culture is a popular form of hydroponics due to the ease of entry and minimal skill required. Essentially, plants are grown with their roots submerged in a nutrient solution which is aerated using an air pump. However, it does pose a few challenges for commercial growers including:

Water Culture Hydroponics
Like many other hydroponic techniques, water culture suspends plants while submerging their roots in a nutrient solution. This method works best with wet-root fruits and vegetables.
  • Some plants, such as peppers and raspberries, require a high amount of aeration, while celery, cabbage, and asparagus tolerate wet soil and water culture hydroponics very well.
  • DWC systems and reservoirs should be routinely inspected and cleaned to prevent bacteria and fungus from infecting the plant roots. Air pumps help prevent DWC reservoirs from becoming stagnant. However, increased bacteria is still a risk factor.
  • Water culture setups can become heavy to move, transport and stack, making it costly to scale in a smaller facility.

#2. Wicking Systems

Just as the name implies, this hydroponic method uses a wick to coax the nutrient solution up into the hydroponic substrate, feeding the plants (more on hydroponic substrates later). Wicking systems leverage the capillary action of water to draw nutrient solution up a wick, much like water moves up a paper towel when you dip one end in water. The liquid is then distributed to the roots via a hydroponic substrate (or soilless medium).

The hydroponic wicking method is possible through a phenomenon known as capillary action. Tiny blood vessels like tubes inside a plant (called xylem) enlist the forces of cohesion, adhesion, and surface tension to transport water and disolved nutrients throughout the plant.

This system keeps the roots from being submerged in water for long periods of time and allows the plant’s roots to breathe. Wick systems generally work great for growing cannabis, especially if you are not implementing a vertical farm. That said, there are a few instances a wicking system may not be right for your facility:

  • Nutrient uptake is bottlenecked at the wick. This could hinder the growth of larger plants that require more water and nutrients.
  • Although wicking allows for better aeration compared to DWC, roots are always exposed to water. This hinders more advanced cultivation techniques such as crop steering.

#3. Ebb and Flow (or Flood and Drain)

When using water culture techniques, the roots are continuously submerged in an aerated nutrient solution. And as we said, this greatly limits the cannabis root’s air exchange. Ebb and flow methods secure the plant structure, and then use a flood-and-drain cycle to fill the reservoir or substrate with dissolved fertilizer, and then drain the solution so the roots can breathe. Challenges associated with an ebb and flow system are fairly straightforward, and include:

  • Mechanical, moving parts such as the pump. More moving parts mean at some point additional maintenance will be required.
  • The pumps used in this method need to be reversible. Some flood and drain systems use a gravity drain. For this model, several variations exist. Be sure to use the best method for your budget and cultivation facility.

#4. Nutrient Film Technique (NFT)

NFT hydroponic systems want to have their cake and eat it too. As the roots of a cannabis plant grow, only the lower parts are fertigated by a thin film of nutrient solution. This technique makes it easy to inspect the roots of your plants, addressing nutrient ratios and infection issues early. And because only the lower roots are rinsed in solution, the rest of the root structure is exposed to the air so the roots can breathe. Here are a few things to consider before implementing an NFT technique:

Nutrient Film Technique
Using the nutrient film technique, cannabis plants are grown by suspending the bottom of their roots in a very thin layer of nutrient solution. This provides the plant food while allowing for critical root respiration.
  • Nutrient film systems are subject to pump failures, much like that of an ebb and flow system. Even if your pumps are in good condition, power outages can quickly leave exposed roots susceptible to dry-out conditions.
  • Water is one of the best thermal conductors, meaning, it gains and loses heat quickly. As such, when transporting your nutrient solution longer distances (such as on a vertical farm), it’s important to ensure the temperature of the water farthest from the reservoir is still optimal and not too cold.

#5. Drip System

Using a drip system carries many of the benefits of a wick system while mitigating some of the disadvantages. Like NFT and ebb and flow methods, drip hydroponics are considered “active” systems, in that there are moving parts (primarily the pump). Most drip systems use a hydroponic substrate or an inert vegetative support medium to anchor the plant during growth. Drip systems work well with most hydroponic crops. However, it’s important to consider:

  • Drip systems are dependent on electricity and optimal pump functionality. Be sure to frequently inspect your pump and have a contingency plan should there be a power outage.
  • Drip systems require a bit of piping to get nutrients to your plants. It’s important to routinely manage your water quality, tubes, couplings, and other hardware.

#6. Aeroponics

Although not the most common, aeroponics is often considered the most modern and sophisticated hydroponic technique. In an aeroponic system, plants are often structurally stabilized using plant collars made from foam or plastic materials. Then a spray system mists the cannabis plant roots with a nutrient solution. Beyond this basic concept and as with other hydroponic methods, grow setups will widely vary from cultivator to cultivator.

This technique provides the roots with an optimal balance of nutrients, water, and air. This makes aeroponics perfect for cloning because spray systems (such as EZ Clone) can be configured to provide the perfect environment to persuade a delicate cannabis trimming into growing new roots.

Aeroponic systems are great for vertical farms and gardens and can be built just about anywhere. This technique focuses on the technicalities of root health, however, for some growers, this advanced form of hydroponics may not be feasible for beginners for the following reasons:

  • The plant and its roots are highly exposed to the environment. Without temperature stabilizers such as soil, it is critical to maintain optimal, root zone conditions for your suspended plants.
  • Setup costs are generally higher than alternate hydroponic systems.
  • There are a lot of parts to maintain – especially spray nozzles and pumps. Over time, nutrients can clog your nozzles, reducing their ability to evenly mist the roots of your plants.

The Best of Both Worlds

From these six hydroponic techniques, over a hundred variations have sprung up as cannabis cultivators innovate and scale for success. The goal of each of these methods is to provide dialed-in liquid nutrients to the roots of cannabis plants while providing sufficient physical support for the stem, leaves, and produce. Sometimes the physical support is a substrate and sometimes it’s a plant collar or basic structure used to support the plant and suspend the roots.

Most hydroponic techniques can be separated into two categories: methods that use a hydroponic substrate and methods that rely solely on nutrient solutions and root suspension. Hydroponic methods that frequently use an inert substrate, such as ebb and flow and drip systems, offer many benefits to commercial cultivators. Leveraging an inert growing medium (i.e., hydroponic substrate) naturally encourages your plants to grow stronger, healthier, and produce higher yields.

What Is a Hydroponic Substrate?

First thing’s first: what the heck is a substrate? The word is vastly broad and spans industries such as construction, electronic manufacturing, and farming to name a few. Narrowing things down a bit, Merriam-Webster defines a substrate as, “the base on which an organism lives.” And in agriculture, the largest substrate in the world is field soil. Plants root themselves in the earth, and they obtain nutrients and water from the soil substrate.

Unlike fertile field soil, a hydroponic substrate should be as chemically inert as possible. This is because you want your plants to uptake your tailored, uncontaminated nutrient solution. If your substrate is chemically attracted to your nutrients or sheds various chemical compounds, it can negatively affect the development of your plant.

High-performing soilless substrates should also be able to retain water while allowing for adequate aeration. Again, the goal is to provide your cannabis plants with a steady supply of clean food and water, while allowing the roots to respire.

Organic and Inorganic Soilless Mediums

Although hydroponic substrates may be soilless, that doesn’t mean they can’t be organic. And to clarify, when we discuss “organic substrates,” we are referring to the fact they were manufactured from materials that were once living things such as plants or animals. A capital “O” Certified Organic substrate is a growing medium that has been certified by the USDA. This can boost your brand’s reputation, but it’s not necessary to operate a successful business.

Inorganic soilless mediums such as Rockwool and perlite are currently the industry standard in hydroponics. However, organic substrates like coconut coir and peat moss are becoming increasingly popular because they retain a great balance of water and air. Although a significant amount of time and processing goes into manufacturing coco coir, companies like Botanicare and Hawthorne are always looking to develop more sustainable manufacturing techniques.

Regardless of whether an organic or inorganic substrate is used, cannabis cultivators have many options available. In fact, growers have had great success cultivating cannabis using both organic and inorganic substrates. As a quick reference, we’ve included a brief chart below with examples of each:

Inorganic SubstratesOrganic Substrates
Rockwool / StonewoolCoconut Coir / Coco Coir
Perlite / VermiculitePeat Moss / Sphagnum
Clay Pebbles / Expanded ClayRice Hulls
Sand / GravelSawdust
Both organic and inorganic substrates can be used for the hydroponic propagation and cloning of cannabis plants. Each has its advantages and challenges. When growing cannabis, the properties of soilless substrates such as coco coir, perlite, and Rockwool offer distinct advantages to cultivators.

The Pros and Cons of Inorganic Substrates

The beauty of hydroponic farming is that you can grow plants just about anywhere, using what you have in your environment. Sand and gravel provide structural support and aeration but drain much too quickly and completely for most commercial hydroponics. And due to the sheer weight of the substrate, it would be ill-advised to attempt a vertical farm using such materials.

As we mentioned, Rockwool (or Grodan) is an industry standard in hydroponics. This is because it provides the cannabis plant with support for the main stem and roots and can be found with an electrical conductivity of zero along with a pH of 7 (neutral). This makes it easier to balance your nutrient solution for optimal uptake.

Rockwool is also used as building insulation and the materials can be dangerous to manufacture, causing skin and lung irritation if proper precautions are not taken. And then there are environmental concerns given Rockwool does not decompose, although it can be chopped up and mixed into potting soil after being sterilized.

That said, Rockwool is still a great option for hydroponic farming. It ensures your plants are exclusively uptaking your nutrient solution and are convenient to transport and set up due to their size and weight. Most of all, Rockwool provides moisture retention without sacrificing aeration. However, cultivators have a couple organic options that can often outperform the molten-rock spun materials.

Coconut Coir as an Organic Hydroponic Substrate

Although inorganic substrates like Rockwool have proven to be effective growing mediums, many farmers continue to search for soilless solutions that won’t add to landfills. Sphagnum moss (peat moss) provides a great environment for cannabis roots. However, it’s not considered renewable as it can take peat moss 20 years to grow a single inch.

Then there is coconut coir. A product manufactured from the coconut industry’s waste stream. Coconuts are used to make everything from cooking oil to cosmetics. Millions of tons of coconuts are harvested each year worldwide, and with few exceptions, a significant amount of husks are disregarded as waste. Fortunately, with some agricultural ingenuity, these husks can be transformed into the organic substrate, coco coir.

What Is Coco Coir?

The anatomy of a coconut consists of three layers. The outermost shell (or skin) is called the exocarp, and it provides first-level protection against the elements and pests while the fruit is developing. The second layer as we grind deeper into the fruit is called the mesocarp, which we also call the “husk.” Finally, the third layer is called the endocarp, and this is the shell that protects the inside of the seed.

“Coco coir”, “coconut coir”, “coconut fiber”, and “coir” are all terms used to describe the fibers and pith processed from the coconut husk. The husks are soaked anywhere between several days to several weeks, loosening and softening the fibers. During the process of separating the husk fibers, coco pith (also referenced as coconut dust) separates from the fibers. Coconut pith represents about 25% of the husk and has excellent water-retention properties.

Coco coir is manufactured from the compressed fibers and pith found in the coconuts mesocarp. This middle layer is commonly known as the husk and is found between the outer shell and the meat inside.

After processing the husks and preserving the pith, the coir material is rinsed to remove the high salt content from the coconut coir. This is especially necessary if the coir is going to be used in hydroponic farming. Coconut trees thrive in warm environments that are close to our saltwater oceans. In addition, to reduce the usage of freshwater, the coconut husks are often soaked in readily available saltwater.

Using one of many processing techniques, the pith is reintroduced to the fibers and coco coir is born – a natural, hydroponic substrate perfect for growing cannabis! As coconut coir manufacturers continue to find ways to make the processing of the husks more efficient, the use of coco coir will continue to grow as a sustainable option, while also providing cannabis cultivators a substrate that naturally encourages stronger roots and healthier plants.

The Benefits of Using Coir for Cannabis

The old phrase, “out of sight, out of mind” is not advised in the business of cannabis cultivation. In fact, paying attention and having detailed data on your plant’s root zone is critical in growing large, high-yielding cannabis plants. The root zone is the area in the substrate where a plant’s roots reside. An optimal root zone will provide the roots with:

  1. Adequate air surrounding the roots to facilitate aeration.
  2. Nutrients and moisture for the plant to uptake during both vegetative growth and flowering.
  3. Distribute nutrient solution evenly throughout the substrate to support increased uptake as the roots grow and expand.
  4. Support optimal pH and EC levels by leaching or dispersing as few cations as possible.

Coconut products that use coir manufactured from the husks provide a natural substrate option for hydroponic cultivators looking for the benefits provided by hydroponic farming while using a substrate that is mostly inert to provide the structural support a large, mature cannabis plant requires.

Crop Steering With Coco Coir

The technique of crop steering refers to the management of a plant’s environment to “steer” it towards vegetative or flowering growth cycles. For example, a clone or seedling will require more water to support strong, vegetative growth. Later as the plant matures, you may wish to reduce the amount of water and nutrient solution to promote deeper, stronger roots or as part of ramping up its flowering cycle.

This becomes a challenge when you’re using a hydroponic technique such as deep water culture, an ebb and flow system, or other methods that continually provides water to the roots in a systematic, consistent cadence. Although controlled liquid delivery is only one element of crop steering, it’s a significant one you’ll want to have the ability to adjust. Conveniently, coco coir products allow exactly that.

A huge aspect of crop steering is crop registration, and we’ll jump into that topic another time. Suffice to say, this is the process of collecting data on your plants for use in growing homogenous plants or crop steering. Crop registration can include a variety of data from substrate pH and electrical conductivity (nutrient concentration) to the diameter of the stems and their height. You want the plant to have enough vegetative mass to support all those buds you’ll be growing during the generative cycle.

The more you document during the growth and maturation of each crop, the tighter you can make your fertigation protocols to maximize the potential of each harvest. Coco coir products allow a farmer to use the data collected on their plant to make precise adjustments to the plant’s root zone.

CocoPro Cubes – Combining the Science of Coco Coir and Fabric Pots

Let’s take a quick look at a CocoPro cube – a product deliberately designed to maximize a cannabis plant’s size, health, and yield. The fibers used in a coir product provide both plant stability, as well as superb aeration, allowing the roots to respire. The water-absorbent pith integrated with the fibers provides excellent moisture retention. Together, the fiber and pith provide an ideal hydroponic substrate for commercial cannabis growers.

CocoPro and Fabric Bags
Coconut coir is washed and buffered to provide excellent drainage, aeration, and support for your cannabis plant. CocoPro cubes use a fabric bag to help mitigate serious issues such as root rot and root binding.

Hydroponic substrates such as CocoPro have been optimized for cannabis cultivation in a few ways, including:

  • The coir has been washed and buffered without the use of solvents, providing a chemically stable substrate.
  • An optimal ratio of fibers and pith – providing an even distribution of nutrient solution while supporting respiration in the root zone.
  • The coir cubes are manufactured with consistency in mind. Growing in a consistent substrate allows for consistent nutrient uptake yielding consistent results crop after crop.
  • Coconut coir does not become hydrophobic as it dries. When crop steering towards generative growth (flowering), you can minimize how much nutrient solution is used to stress the plant without compromising nutrient absorption. This means that even when watering in smaller amounts, your solution will continue to be evenly distributed throughout the root zone.

CocoPro cubes hydrate in a specialized bag that allows the coir to breathe and helps mitigate harmful root zone issues like root rot. The fabric bag also helps prevent the roots from becoming clumped or bound. When the roots reach the edges of the bag, they stop growing until they are transplanted or have reached the desired size. The results are much like those when using fabric pots – more efficient nutrient uptake, healthier plants, and higher trichome yields.

Choosing Your Hydroponic Substrate

Hydroponics is increasingly becoming a popular cultivation method for cannabis farmers looking for precise control over their plant’s environmental conditions. Light, water, air, nutrients, and CO2 are all needed to grow cannabis. However, if you want your plants to thrive, a cultivator will want precise control over all of these factors.

There are many ways to accomplish this, and coco coir is certainly one of the most affordable options to enter into commercial hydroponic cannabis cultivation. If you have any questions on designing a grow facility or which hydroponic products and techniques are best for your business, feel free to reach out to us here. We’d love to chat!

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