By Erik Biksa and Danny Danko
Why Grow Hydro?
While soil is forgiving for first-time growers and allows the use of a wide variety of fertilizers and supplements, including organics, the levels of dissolved oxygen at the roots of a plant grown in soil are relatively low compared to a well-planned hydroponics system. In soil, plants have to compete with other organisms in the rhizosphere (root zone), such as fungi and bacteria, to extract nutrients and other essential building blocks—and while there are many microbes that work symbiotically with the plants, assisting them in absorbing these materials, the fact is that plants grow fastest in a sterile root environment with plenty of oxygen. Pure and uninterrupted absorption of oxygen, water and minerals provides everything that a healthy plant craves—with nobody else cutting into the chow line.
Hydroponic growing can also help to conserve water and allows for much higher yields in the same amount of space. In some systems, the nutrient solution is rarely (or never) dumped during cropping, and in some instances the “used” solution can be pumped to feed mineral-hungry plants outdoors -- all of which can make hydroponics a lot friendlier to the environment as well.
Additionally, hydroponic planting mediums that are chemically stable and inert, such as grow stones, can be reused many times, thereby lessening the environmental footprint created by the grower. For example, consider that peat bogs,
which can take tens of thousands of years to develop, are stripped to supply “throw-away” soils that are replaced with every crop. The reuse of grow stones also means that less fuel is ultimately consumed for the long haul transporting (and frequent replacing) of your medium.
Benefits of a Sterile Environment
Maintaining a sterile environment can also have other advantages in the age of medical cannabis cultivation. Where there is a risk of microbial contamination in plants grown from soil for patients with sensitivities, in hydroponics there is no microbial life introduced from the medium -- or potential pathogens and insects from other food sources -- into the growing environment, because the medium and method keep that environment sterile. So in addition to plants being able to grow faster in controlled, oxygen-rich conditions, we can see the other benefits: reusability, the potential for water conservation, and a greater chance of maintaining a pathogen-free environment.
Root temperature is a serious growth factor often overlooked even by seasoned cannabis cultivators in their quest for bigger yields of better buds. Every grower knows how important it is to maintain the right air temperature, which changes during a cannabis cropping cycle, for better results -- so why not pay attention to the roots, too? (It pays to honor your roots!) In hydroponics, the root zone can be controlled with precision -- and not just in terms of temperature, either.
All of this sounds promising enough in theory -- but what does it deliver in practice?
Faster Growth Rates
For a lot of growers, especially those who follow the guidelines outlined here, using hydroponic techniques will lead to increased growth rates. That means harvesting in less time, which for serious growers or those dealing with medical necessity means shorter waiting periods between harvests and achieving more harvests in a calendar year.
And if you get serious about hydro, it can mean bigger yields, too. But don’t jump into the deep end of the growing pool and expect to avoid making some splashes while you get your hydro routine fine-tuned over the course of a couple of crops -- especially if it’s your first time getting wet, so to speak.
While hydroponic growing is a powerful tool, there are some fundamentals that need to be learned for success. For heightened yields, it may also take some practice, although just by maintaining the basics you’re almost certain to see faster growth rates, more tidy and efficient cropping, and potentially less time required in the garden -- especially if you aim to eventually graduate to automated hydroponic growing.
In other words, learn the essentials first, and you will see that growing cannabis with hydroponics doesn’t have to be complicated or even expensive: just manage your crop, your budget and your expectations accordingly, and you’ll be sure
to have some fun -- while reaping benefits in terms of better buds -- by sticking with our hydro fundamentals.
By definition, water is the growing medium in hydroponics. For practical purposes, if any additional medium is used, it’s simply to anchor the plants and provide contact for their roots with the nutrient solution. Here is the fundamental difference between soil growing and hydroponics: in the latter, the food for the plant is in the nutrient solution rather than the soil itself. When cannabis is grown hydroponically, it has a more direct relationship with the fertilizers and supplements you provide.
By the same token, while this relationship promises incredible crop-feeding power, it also makes hydroponics less forgiving than soil. In hydro, you can see changes in your plants within hours, while with soil it can take days -- there’s no pH or nutrient buffering in a true hydroponic medium. Grow stones and light expanded clay aggregate (LECA) are true hydroponic mediums because they don’t have any buffering capacity. Coco coir and rockwool are also excellent (and popular) choices, while providing some buffering and/or ion exchange.
Some hydroponic systems use no medium at all; the plants are simply supported by plastic collars or baskets while the bare roots are bathed in an oxygen-rich nutrient solution or mist. Needless to say, fast growth and no medium to replace can be enticing benefits for indoor growers.
You can grow hydroponically even with water of marginal quality, but for healthy cannabis crops with increased growth rates and yields, you’re going to want to use the best-quality water possible. For a lot of serious hydroponic growers,
this means adding a reverse-osmosis (RO) filtration system to remove all impurities from the water that could affect the nutrient chemistry supplied in high-end fertilizers.
As a rule of thumb, if the untreated water doesn’t taste good to you, it probably won’t taste good to your plants. Sadly, some water supplies are toxic and shouldn’t be consumed by anyone -- especially by plants for medicinal consumption. If your water is less than 150 ppm in dissolved solids (about 0.2 EC), it’s probably just fine to use with a quick pass through a sediment and carbon filter -- thereby eliminating the need for wastewater-intensive RO filters.
Also, as a compromise, there are “hard water” nutrient formulations available from some manufacturers of specialty hydroponic fertilizers. Typically, they will contain less sulfur, magnesium, calcium and iron than conventional hydro formulas.
This is very likely where the magic of hydroponics resides, as dissolved oxygen (DO) levels are often the most overlooked factor in generating a higher degree of health, growth and yield in cannabis plants.
Plants with elevated DO levels at the root system are less prone to cropping problems and can use nutrients more efficiently. When super aeration is applied to bare root systems -- for example, in a deep water culture ((DWC) system at a rate of 1.5 liters per minute (LPM) of air via high-output aeration pumps and airstones -- the amount of fertilizer used can be cut in half, or even by as much as 75 percent, versus conventional soil or soilless growing methods.
Some growers may be astonished to learn that they can maintain giant plants with a scant 400 ppm nutrient concentration, simply because the plants will process the nutrients more efficiently with the super lev- els of oxygen available at the roots.
Around 0.75 LPM of aeration is plenty, but around 1.5 LPM is when you really see things start to surge. This means you should cut back nutrient strength proportionately with the level of aeration versus standard growing methods (though keep in mind that amounts will vary from system to system and situation to situation).
However, poor aeration -- especially when coupled with warmer temperatures -- can spell disaster in a hydroponic system. Some strains will be more prone to root rot than others, although it’s wise to take every precaution: Anaerobic conditions can be your number one threat in hydro versus soil gardening.
Besides pumping air into the solution, moving the solution through the air -- i.e., the nutrient return splashes into a reservoir -- is a highly effective way to introduce more oxygen into the solution and, ultimately, to the roots of your cannabis crops. If you maintain a reservoir, adding a small circulation pump to keep the solution stirred (especially between applications, as with flood-and-drain setups) will help to improve growth rates and cut down on problems by making more DO available for the roots.
In this respect, it’s much like an aquarium, where the fish need oxygen in the water.
While worrying about air temperatures up top, a lot of growers overlook what influence temperature has down below, at the root zone. Hydroponics affords a level of precise temperature control at the roots via the nutrient solution’s temperature and the overall volume of solution that surrounds the roots. For example, if your growroom runs warmer than optimal, keeping the roots bathed in a highly oxygenated and chilled nutrient solution can provide the necessary balance for healthy growth.
Plus it’s more efficient, in terms of electrical consumption, to keep the root zone a few degrees cooler with a reservoir chiller than it is to cool the entire growing area.
In nature, the soil stays an even, cool and comfortable temperature -- even when it’s sweltering up top at noon. The same principle applies here.
The fact that cooler water holds considerably more dissolved oxygen than warmer water is another big plus for having a reservoir chiller. At the same time, however, cool basement floors in the wintertime can hurt growth. If the root-zone temperature stays below 65°F, nutrient uptake can become limited -- so while you don’t want your plants’ roots to overexert themselves in the heat, you don’t want them to hibernate, either. An aquarium heater can keep the reservoir temperature steady at whatever set point you desire during the cooler months. Most growers find a reservoir temperature of 67°F to be optimal.
To promote brighter colors and firmer buds at harvest, instead of trying to cool your whole growroom down, you can simply chill the plants at their roots. Purples show up in days instead of weeks when you chill your solution below 57°F during the final days of cropping before buds are harvested -- for example, during the flush period. The extra stress can contribute to a higher resin content, too.