Maybe you heard about hydroponics from other growers, who praised its control and efficiency. Maybe you saw a grower touting their large hydroponically-grown buds on Instagram, or maybe you’re just interested in automating your grow operation and want to learn what role hydroponics can play in that endeavor.
Whatever the reason, hydroponics is a popular option among growers. So here and now we’re going to briefly cover what hydroponics is, what the various setup options are, and a few tips and tricks to keep in mind if you decide to try it out.
Hydroponics is one of those terms that has a different definition depending on the community you ask about it. Ask a member of the public, and they’ll probably tell you that hydroponics is growing a plant in water, where the scientific community defines hydroponics as plants growing in an inert, non-organic medium. For our purposes, we’ll go by the scientific definition for accuracy’s sake. This will rule out some setups that look very much like hydroponics, but that distinction is not trivial.
The reason for this actually gets right to the heart of one of hydroponics’ main draws, that it offers a high degree of control to the grower. When you’re growing in soil, it can be difficult to know for certain that the nutrients you’re giving to the plant are actually being absorbed. You can’t dig up each plant’s root system and measure the quantity of nutrients remaining, to check that your plants have had their fill.
The growing medium in a hydroponic system doesn’t hold on to nutrients as much as soil does. So, if you measure how much of a given nutrient you’re putting into the irrigation water, and measure how much is left after the water has been given to the plants, you can be fairly certain that the difference is how much nutrients the plants have taken in.
That ease of measurement and monitoring is valuable, but it does come at a price. Soil is usually recommended to novice growers because it gives the plants a buffer from adverse environmental conditions. Particularly in systems where the root systems are exposed to open air, a break in the irrigation/feeding schedule can be disastrous.
This is not to say that first-time growers can’t make hydroponics work, and work well. What it means is that any grower considering a hydroponic setup for their grow room should be giving serious consideration as to how they’ll be absolutely certain that their plants’ needs are being met.
For the owner/operator, or smaller grower, that can just mean you have to schedule your time very closely. For a larger operation, that can mean prioritizing attention to detail and adherence to your standards among your supervisors or considering installation of an automated control system. It certainly means having answers to questions like ‘what if my neighborhood loses power?’ and ‘what if my ventilation breaks down?’
For those willing to face those risks, hydroponics can let you grow quickly, very quickly. “In general, the whole advantage to hydroponics is that the plants can absorb the nutrients at a much faster rate,” said Dan Canose, Northwest Regional Manager for Botanicare, headquartered in Chandler, Arizona. “Plants grown hydroponically typically grow much faster than they would in soil, because they don’t have to spend the latent energy that it takes to extract nutrients from traditional soil.”
Canose explains that hydroponics systems can run the gamut from the simple to the complex, depending on what the grower wants, and how much they’re willing to spend. “The most basic kind of hydroponics is a wick system, where your plant is suspended in an absorbent growth medium with a wicking material that physically connects it to the water.”
Wicking material doesn’t have to be fancy, a simple length of cotton rope will suffice. The magic of capillary action will act as a siphon, pulling water up the rope as the plant drinks it in. Feeding the plants is as simple as mixing your preferred ratio of nutrients into the reservoir the wick is pulling water from.
Wick systems have a few basic advantages: they’re cheap, they’re simple to build, and capillary action doesn’t care if the power is out, so as long as your reservoir is full, your plants can water themselves. On the other hand, by letting physics do your watering for you, you’re giving up a degree of precision and control over how and when your plants are fed, which is what attracts many people to hydroponics in the first place.
If you’re willing to make something a little more involved, another common option is to outfit your budding cannabis crop with a drip irrigation system. For many drip irrigation systems, the design is awfully similar to a wick system: there’s a central reservoir, and water goes from it through a system of tubing to each plant. However, there are some pivotal differences between the two.
First is that a drip system is going to require a pump to get the water to flow uphill through tubes to the plants. David Dudley, director of commercial sales for Grow Generation in Denver, Colorado, described a simple setup starting from the outlet of the pump in the central reservoir. “You’d put a bubbler in the vat, a multi-bubbler with eight outputs,” he said. “Then you would run a four-inch line from each output on the bubbler to each plant site. A lot of times, people will do two per plant site, in case one gets clogged.”
Clogging is an important consideration when you’re considering a hydroponics system. When you add nutrients, you’re adding particulates that can clog the line, and prevent water from getting to a particular plant. If the dripline you’re using has small emitters, you may also want to think twice about burying it in your growing medium. Plant roots will seek out and grow towards water, and can grow right into the emitters, clogging the line.
Installing two lines per plant is one way to insulate your system against clogging. If you’re concerned about root intrusion in your setup, some companies embed their tubing with herbicides, or infuse their emitters with copper, to prevent intrusion. Whatever technical methods you may choose to employ, monitoring for potential clogs is an important safety measure. Again, in a hydroponic system, plants are more sensitive to underwatering than a plant in soil.
If you’ve got the space and don’t want to deal with sending tubes out to individual plants, there are hydroponic setups that offer easier scaling options. One of the most popular options here is the ebb and flow system. In this setup, plants grow in trays, supported by a soilless medium. A set number of times per day, the trays are filled with nutrient-rich water from a central reservoir and allowed to drain.
Being organized into trays helps with maneuverability and scalability (instead of hooking up one plant, you hook up a trayful) while still keeping a modular system. If a particular plant shows signs of stress or disease, that tray can be removed, examined, and returned with minimal fuss. If an alteration needs to be made to the entire system, you might be adjusting dozens of trays, rather than hundreds of plants.
A close cousin to this system is the deep water culture setup. Here, the plants and their medium are suspended in the central reservoir, or in buckets connected to a central reservoir. It’s a simpler design than ebb and flow, and easier and less costly to build and maintain as a result. Without that added complexity, though, comes with a big drawback: the single point of failure.
Plants ‘breathe’ in CO2 from their stomata, but they also need oxygen at their roots to make use of all those nutrients you’re feeding them. Controlling the amount of oxygen in your water is mostly a matter of controlling the water’s temperature. Cooler water holds more oxygen, but once the water starts to drop below 68 degrees Fahrenheit, the cold can hurt the roots, so most growers aim to keep their water at this magic number.
Central reservoirs, particularly in recirculating hydroponics systems, also need an air pump or air stones. Partly they keep the water oxygenated, but mostly having an aerator prevents a film of bacteria from growing over the surface of the water. Not only is that film foul-smelling, but it can form an anaerobic layer that encourages root diseases.
That’s not to say that a film is always a bad thing. “Nutrient Film Technique, or NFT, is a very popular system, where the roots are suspended in a chamber, and the nutrient solution is actually trickled down the bottom of that chamber in a thin film,” explained Canose. “The potential advantages come out the most when you’re going for more, smaller plants, rather than fewer, larger ones. You don’t use nearly as much water, and there’s still a fair amount of oxygen in that system, so you don’t end up stifling the roots.”
Another technique that avoids using a growing medium is growing increasingly popular for cloning purposes, and it’s called aeroponics. Here, plants are held in place above a nozzle, their roots exposed. Every few minutes, the nozzle sprays the roots with water and nutrient, giving a very precise and constant dose of nutrients to the plants with very little water used in the process.
The control and precision are tough to match with any other method, but aeroponics does leave plants uniquely vulnerable. If the regular sprays are interrupted by a clog or a pump failure, the exposed roots can dry out in a matter of minutes.
For many growers, the potential risks of aeroponics outweigh the rewards, but many growers find that the scale is balanced when it comes to growing clones. Because the roots aren’t planted in anything, aeroponics minimizes or even eliminates the shock of transplanting. As a result, growers have taken to cultivating their clones in an aeroponic system, then switching them to another setup when they’ve matured.
Whichever system you decide is best for you, there are some universal considerations you need to keep in mind. First is that you’re feeding all your plants through a nutrient solution mixed into your irrigation water, so if there’s a nutrient that your cannabis needs, and you aren’t putting it in the water, how can you expect your plants to get it?
Like all plants, cannabis eats up the three main fertilizing nutrients: Nitrogen (N), Phosphorous (P), and Potassium (K). Those are the three biggies, but cannabis also requires a few secondary nutrients, like Calcium (CA), Magnesium (MG), and Sulfur (S). Beyond this, there are other micro-nutrients like Manganese (MN), Boron (B), Zinc (ZN) and Copper (Cu).
How much of each nutrient a plant needs is dependent on its stage, the strain, the grow environment, and is a matter of spirited debate in the cannabis growing community. To help you figure it out, most nutrient providers have a set feeding schedule and a wide variety of products that growers can use to fine tune that schedule to their liking.
So what makes nutrient choice in a hydroponics setup different from growing in soil? Well, you’ll need to be able to recognize and react to a problem in your plants’ nutrient uptake. An imbalance in your feeding, or improper timing of your feeding, can result in nutrient-lockout, where your plants are refusing to eat the nutrients they’re being fed.
Nutrient lockout can occur for a number of reasons. “A lot of times, it’s because too much nutrient was added to the water at one time,” said Canose. “But sometimes, the nutrients were added in the wrong sequence. For instance, if you put in a high phosphorous solution, and then add in a nutrient mix with calcium, the phosphorous that’s still in the water will actually bind with the calcium. You’ll get calcium phosphate crystals that will drop out of solution, and become unusable to the plants.”
Ideally, you want to be keeping a close enough eye on what’s in your irrigation water that you’re never actually seeing the symptoms of a nutrient lockout, but nobody’s perfect. In case you don’t catch a problem in time, it’s a good idea to read up on what different nutrient deficiencies look like in cannabis, so you can diagnose quickly if a problem does appear.
However, you don’t have to wait for symptoms to appear if you’ve got the right equipment. Regular measurements of your waters’ electrical conductivity (EC) and total dissolved solids (TDS) can be used to determine what nutrients are swimming around in your mix. It will take a little time and effort to get a handle on, but if it puts you ahead of the curve on a potential crop disaster, isn’t that time well spent?
Fortunately, for most cases of nutrient lockout, there’s a simple, one-size-fits-all answer: flushing. Replacing the water in your system with fresh H2O will interrupt the banquet you’re giving your plants, but it’ll also provide a foundation for you to rebuild your feeding schedule. Flushing gets rid of whatever unused nutrients were suspended in your old water, and also dilutes any nutrients that had built up in your growing medium.
That brings us at last, but not least, to water, the essence of hydroponics. Standard tap water needs a few modifications before it’s ready to go to your plants, and it’s up to you to make that happen. First of all water, as a rule, is pH neutral, meaning it has a pH of 7. Cannabis wants slightly acidic conditions to grow in, and that’s usually achieved by having a slightly acidic soil, but in hydroponics, it’s usually done by adjusting the pH of the water by adding in an acid or a base.
If you’re already building your system to accommodate changes to water pH, water temperature, and nutrient mixing, it’s not a bad idea to make sure the water coming into your system is properly filtered. It’s a simple measure that can limit or prevent clogging issues, or unwanted nutrients coming into your carefully controlled environment. Particularly if you’re pressurizing your water for pumping or misting, removing particulates can save you a repair bill and lower maintenance costs.
For growers interested in a large-scale or complex hydroponics system, there are many other considerations. Do you want to recirculate your water, or do you want used water to drain to waste? Recirculation is more efficient, water-wise, but it also generates a lot of work, measuring and adjusting reused water. For large scale grow rooms, drain to waste can be easier to deal with, and produce more consistent results.
Although nowhere near an exhaustive list, you also may wish to consider in-line dosing systems, that inject the planned nutrients directly into the water as it comes out of the source, so you don’t have to mix into the central reservoir. Or automating your hydroponics setup with a computer control system.
I’ll let Dudley have the last word, with a good bit of advice he has for first-time hydroponics growers. “I’ll often tell people, find what works for you,” he said. “Everyone’s got their own speed, and their own type of systems they like to work with. Some people like more automation, some people like less, it’s all about finding the style that works for you.”