Photo by Dino Mendoza
Hydroponic weed refers to any cannabis that is grown without the use of soil. Instead of the natural nutrients found in soil, growers will apply their own nutrients throughout the grow process using a variety of growing methods.
While hydro grows are usually less likely to attract pests, hydroponic systems can expose the roots to damage if there is a pump failure or you run out of water. Hydroponic grows also require more maintenance than soil grows because more things can go wrong, a lack of water for a little while or a slight change in pH levels can set back the crop or destroy it. This is why it’s important to start with one of the simpler processes as a beginner.
Despite the extra care required, hydro grows offer growers far more control over the nutrients that go into the plants and allow the water that is not absorbed by the plants’ roots to be recycled back into the system.
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Like any grow method, hydroponics has its benefits as well as some challenges and limitations. Some growers suggest that hydro is the superior method, claiming that since the grower has greater control over nutrient intake plants grown using this method not only grow faster but can yield more smokable flower. To find out if this is true, we asked master grower Jorge Cervantes. What are the major benefits and drawbacks of using a hydroponic system and is there a difference in the quality of the flower produced hydroponically rather than grown in soil?
“On the positive side,” Cervantes says, “hydroponic systems require an inert substrate (growing medium) that does not react with fertilizers. A grower can control the exact fertilizer mix and not worry about extra chemical activity in the root zone. Hydroponic systems are very efficient indoors and in greenhouses. Water can be reused and hydroponic systems are clean.”
However, this system can also be a bit tricky because it does require so much intervention from the grower.
“Diseases can spread through a system quickly, imbalanced nutrient levels are recirculated in some systems and manufacturing and transporting components creates an expensive environmental carbon footprint,” says Cervantes, recommending readers look at the Container Culture and Hydroponic chapters in the Cannabis Encyclopedia for more advice.
According to studies conducted by D.R. Hoagland and D.I. Arnon in the 1950s, hydro does not produce higher yields like some growers claim. Yet a side by side view of soil and hydro-grown cannabis—examples of which can be found easily on YouTube—clearly show that plants can grow faster hydroponically. That is because the plant can absorb its food much faster than it can through soil and its roots systems have more access to oxygen than they ever would in soil. However, as Cervantes points out, soil will hold its nutrients a lot longer than a hydro system and require less tending to.
There are many different kinds of hydroponic grow systems that vary in complexity and offer their own benefits and drawbacks. Ultimately, these systems are nutrient delivery methods which work as a substitute for the natural plant food found in soil. Overall, nutrients can be applied to hydroponic systems through something known as active and passive methods.
Passive methods make use of something known as a medium, which is a substitute for soil, which can hold the nutrients, water and oxygen required for the roots to flourish.
Active methods of growing involve more attention on the part of the grower as they require actively applying the nutrients and allowing them to be recycled. You can also have a non-recycled system that uses the nutrients once, also called run-to-waste systems, but it’s best to avoid these methods since—as the name implies—they are wasteful and could pollute the environment with unwanted compounds that could be recycled as food for your plant.
The drip system is the most common option for hydro grows and one of the quickest since each plant can receive the same amount of nutrients. The nutrients in this system are delivered through a spaghetti tube or mechanism built to ‘drip’ into the top of the pot. The roots receive timer-controlled nutrients from this submerged pump and excess nutrients that are not absorbed by the cannabis leaves, root, etcetera. Can be reused. A drip system needs to be checked frequently due to significant shifts in pH and nutrient strength levels.
The Nutrient Film Technique (NFT) setup is one in which cannabis is planted within netpots with a medium like rockwool. The pots sit on top on an angled channel, usually made of PVC pipe, for the nutrients to flow in a single direction. The roots flow down through the rockwool and pots and into the angled channel where the nutrient solution is poured over them while the excess flows into a reservoir to be recycled.
NFT offers the plants a constant flow of nutrients pumping directly into the grow tray, over the plant roots, and back into the reservoir. No timer is needed for the submersible pump. However, the growing medium, which is mostly air, can be extremely susceptible to pump failures and power outages, which can cause plant roots to dry out fast.
It’s also extremely important to protect the exposed roots from light. This is why master grower Jorge Cervantes suggests that growers avoid using white four-inch PVC pipe. The walls of this piping are thin enough to allow light through which will damage or even destroy the roots.
According to Cervantes’ Cannabis Encyclopedia, this method may need a filter “to prevent debris from blocking the gullies and pump.”
Cervantes suggests that only experienced growers opt for an NFT grow since it is difficult to maintain and requires extreme fine tuning to operate properly. For those who do choose NFT, it is recommended for plants with short grow cycles since the roots could fill the pipes and block the flow of nutrient solution.
The grow tray must be kept humid at all times to protect the roots from drying out and it is also ideal to keep them covered so as not to expose the roots to light. Some growers also paint the outside white to reflect light and the inside black to keep the roots in total darkness.
It’s recommended to check the temperature inside the tubes and ensure that it doesn’t go above 70 degrees Fahrenheit while the oxygen should be at around 8 ppm.
Ebb and Flow systems operate by flooding a grow tray with nutrients which drain back into a reservoir. They use a timer to operate the submerged pump, which is susceptible to pump failures, power outages, and timer failures. These systems are generally considered easy to maintain. They involve a reservoir which is drained and filled several times a day, allowing the roots to soak up both nutrients and oxygen. Individual pots, filled with growing medium, are placed on a growing table which is filled with one to four inches of nutrient solution.
It is best to use heavier mediums for this method as the pots will sit in solution and could float or fall over. In this case rockwool could be best. Ebb and Flow systems rely on the timing of the nutrient delivery. Too few nutrients can kill the roots, but much nutrient solution could deprive the roots of oxygen. (Remember, plants breathe CO2 but roots breath oxygen). That is why it’s important to ensure that the pump system is running at all times and that tray is not flooded for more than 30 mins at a time.
This method is one in which plants hang over the nutrient solution. An air pump releases air to an air stone that discharges nutrients to provide oxygen to the plants’ roots.
The cannabis plants are placed in a small pot, which is then placed in a larger pot, often a bucket which has a hole cut into it to fit the smaller pot but still leave it suspended so that it’s not touching the inside of the larger container at all. The result is that the plant dangles, allowing the roots to grow through the bottom of the initial pot and down into the second larger pot to soak in the nutrient solution. Most DWC grows also keep an air stone pumping oxygen into the solution at all times.
When growing with DWC it is important to allow for dry time for the roots so that they are not constantly submerged in water and can have access to oxygen.
Bubbleponics is a type of DWC which makes use of two pumps, one to aerate the solution in the reservoir and the other to apply the nutrient solution to the roots. The nutrient solution is applied by spaghetti tubes or a top feed nozzle and allowed to flow down through the medium and into the reservoir.
A wick system requires no moving parts and is the easiest system to implement. As Cervantes says, “the more parts in a garden, the more there is to malfunction,” making this system relatively hassle-free. The idea behind this is no more complex than a candle. The grow tray receives nutrients through a wick, made of cotton or yarn, which transfers the nutrients to the roots. However, it is recommended that smaller plants be grown using this system as large plants or plants that need a lot of water may use up nutrient solution faster than it can be supplied. While this system is the simplest it is also the least efficient and could result in insufficient oxygen levels.
Media are the soil substitutes used in a hydro grow. They are made of a variety of different substances that can be placed in the pot to hold oxygen, nutrients and water and are usually inert, meaning they don’t react with any nutrients to affect the plant’s roots. The word Hydroponics is often confused with a similar type of grow system called container culture, which requires not inert media.
Many growing mediums like rockwool, coconut fiber (also called coco peat), gravel or brick shards are not inert and carry compounds that will react with the nutrients that are applied, often helping the growth of the plant, but also potentially hindering it if they are used unintentionally.
Cervantes prefers container culture to pure hydro-grows.
“Soilless mixes such as Peat Lite™ or Fision’s Sunshine Mix® or similar mixes are very easy to use and buffer nutrients,” he says. “Their nutrient buffering ability makes them forgiving. This forgiving quality is essential when temperatures change or nutrients become imbalanced. The buffering ability gives growers time to correct problems. Hydroponic systems with no buffering ability allow no time to remedy problems causing plants to suffer immediately.”
He looks at choosing the right media as a practical labor-saving element. If a substrate is difficult to use, growers will avoid it. Gravel is heavy and difficult to manage and seldom used. Water must be aerated and moving or roots will drown from lack of oxygen. Electricity is required to operate a pump to aerate and move water. If the electricity goes off for more than 20 minutes, roots start to die. A growing medium such as coco coir (ground up coconut husks), however, provides an environment to hold nutrients (fertilizer) that is absorbed by roots.
Well, it’s air. This can be a very effective medium since roots require an abundance of oxygen to grow, but it is also necessary to ensure that there is consistent humidity so the roots don’t dry. This medium is often used in aeroponic systems and partially in the NFT.
On its own, water is not the ideal medium, but systems like DWC make use of water as a primary medium. What growers should keep in mind when using water is that it has to be aerated using a pump or air stone to ensure that plants’ roots can get enough of the oxygen they require.
Probably one of the most popular options for hydro grows, rockwool holds water and air very well and is a stable medium for the roots to take hold in. The drawback is that it can have a high pH content so it may take some balancing.
These little, round, clay pellets are also known as hydroclay or hydroton and are an excellent medium. Each pellet has tiny holes that hold nutrients and air. Though the roots will become quite tangled by the time the plant is ready to harvest, hydroclay is a reusable medium that can be sterilized by soaking it in a mixture of water and hydrogen peroxide.
This medium is made of volcanic glass or sand. It holds air and nutrients, but is very light and does not buffer well because it cannot hold on to the nutrients very long. This fragile material also tends to wear down after use making this medium best for mixtures of inert and non-inert grow combinations.
This substance does exceptionally well at holding water and is recommended by growers like Cervantes for planting clones that need to take root. Vermiculite also has traces of minerals like Silicon, Magnesium, Aluminum and Phosphorus. However, Cervantes warns that you should avoid using construction grade vermiculite because it can contain toxins which will harm your plant.
Jorge Cervantes has taught millions of growers around the world to cultivate cannabis during his four-decade career. Jorge’s books appear in eight languages and hundreds of articles, which can be found in 10 languages. See his YouTube channel or his website for free information. You can also get his definitive book Cannabis Encyclopedia on Amazon.
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