By Nico Escondido


Hydroponic gardening has become one of the most popular methods for indoor cannabis cultivation over the past two decades. We all know that hydro has the potential for big yields and excellent quality, but getting there isn’t always easy. That’s why we’ve dedicated the February issue to hydroponics for the past 12 years. The growroom shot exclusively for this year’s Hydro Report is perhaps one of the best ever recorded by HIGH TIMES – and, of course, its home is in the great state of California.

Mind-Blowing Marijuana

Let’s take a look at the questions that everyone wants answers to: What type of hydro system is running in this room? How many plants are in there? How many lights were used? How much did this room yield? HOW DID THEY DO IT?!?



Beginning at the end is a good place to start so that we all understand exactly what we’re dealing with. This is a professional-grade, very high-end commercial grow operation where no expense was spared. Unfortunately, this system is definitely not something you can set up overnight. The room yielded, at its peak, 37 pounds of primo Blue Dream. That works out to just over 0.75 grams per watt, as the room carried 22 1,000-watt high-pressure sodium (HPS) lamps. When it comes to massive, industrial-sized hydroponic systems, this yield is certainly above the average of 1 pound per 1,000-watt lamp (roughly 0.50 grams per watt).


But the most impressive thing about this hydro room was the sheer size, layout and overall environment created by the growers and growroom architects. Upon walking into the brightly lit room, it immediately became apparent that this was a sterile environment. Everything was keep extremely clean and in order. Floors were regularly washed and swept; walls were whitewashed with glossy white paint; and there wasn’t a single insect or hint of mildew to be seen anywhere. Even the 500-gallon reservoirs were drained and hand-scrubbed, inside and out, every few weeks. These growers took serious pride in their work, and it showed.


Holding a total of 352 plants in 11 raised 4' x 8' trays (32 plants per tray), the room had two 1,000-watt HPS lamps over each table. Plants were grown out of 5-gallon smart pots, which are basically fabric container bags that offer excellent breathability so that root systems get the oxygen they need (remember, roots use oxygen while leaves use carbon dioxide) and the root zones maintain a constant cooler temperature (the roots of mature plants generally like a temperature of 75°F). The medium used in the containers was a simple homemade mixture of coco coir and perlite at a ratio of two parts coco to one part perlite. This combo aided in creating an airy medium for optimal air penetration as well as good water retention, keeping the root zone moist at all times.


The reservoirs used in this system were two light-sealed, 500-gallon cylindrical tanks. One was a backup tank with a reverse-osmosis (RO) filter that fed the primary nutrient tank with fresh water. To top it off, the main tank was insulated and chilled with a 2-hp (horsepower) water chiller, thereby decreasing the chances of mold or other pathogens growing inside.


The system itself that fed off these massive water tanks utilized a full constant-pressure, top-feed, drip-irrigation system controlled by a Rain Bird sprinkler timer. Each tray had its own solenoid, meaning that each one operated as its own zone on the timer. Dual sediment reducers (filters) were on the lines coming out of the feed tank, both before and after the constant-pressure pump. That pump was an out-of-tank, high-end, 1-hp unit (manufactured by Brighton Irrigation) that maintained a constant and equal pressure at all of the drip-emitter sites from water on to water off. The drip emitters were actually yellow-top high-pressure emitters that spray out the nutrient solution, creating a nice, even foam on the surface of the medium that helped the water and nutrients to penetrate and fully soak down. These high-pressure emitters sat atop small stakes that moved easily around within the containers as the root systems expanded. All runoff was drained from holes in the bottom and sides of the containers and then collected by trays and run directly to waste (i.e., to a drain so as not to be reused). Every plant was fed twice a day for 30 seconds, and each tray table was watered in a rotation, one at a time, so that each feed cycle lasted approximately six minutes (12 minutes total for the day) for the entire growroom.


Finally, when it came to atmosphere control, these growers spared no expense, dropping in two 5-ton AC units, one of which was sunk into a specially constructed back room next to the garden that exhausted to the building’s exterior, and the other of which came standard with the building site and sat on top of the roof. The room as a whole operated at a cool 68°F, even in the middle of a California heat wave. Some of this temperature control also had to do with the fact that the 2' x 6' walls of the room were insulated with top-of-the-line R-19 Pink Fiberglas insulation and then covered with a layer of soundproofing. The growroom was 100% light-, sound- and air-sealed, which added an extra layer of security for both the growers and the garden. Because the garden’s air was kept on a closed, recirculating system, no airborne pathogens could penetrate the room, keeping pests and diseases outside. As the two industrial AC units cooled and circulated the growroom air, six carbon Can-Filter 150s scrubbed it to reduce odors and remove impurities. These filters were fitted with 14" flanges and corresponding maximum-cfm inline fans to move the air through the filters and back into the growroom.

Understanding Hydroponics

Strictly speaking, hydroponics is the growth of plants in a soilless medium. Thus, there are technically quite a few grow mediums available these days that would fit this category of growing: rockwool, clay aggregates, lava or volcanic rocks, coco coir, perlite and vermiculate, just to name a few. Then there are soilless mixtures that look and feel very similar to earth topsoil, but are actually sphagnum- or peat-moss-based.


Another component of hydroponic gardening – one that isn’t actually a part of the definition of the term “hydroponics,” but is almost always found in any hydro system – is the automated water delivery associated with hydro growing. The amazing setup described here is technically known as a top-feed drip-emitter system, though in this case the “drippers” were actually high-pressure spray emitters. The plants themselves grow on the kind of tray tables traditionally used in flood-and-drain (or ebb-and-flow) hydroponic systems; these trays are flooded so that the medium can soak up the nutrient solution. The solution then runs out of the containers and is collected by the trays, which either drain the solution to waste, or back to the reservoir to be recycled.


Recycling nutrient solution can be a dangerous move, as it requires diligent measuring of pH and EC levels. Reusing nutrient solution can cause large fluctuations in these levels with each use and subsequent runoff and recollection. This creates the need for more reservoir changes and man-hours of effort. Recycling systems aren’t for growers who simply want to plug in their system and walk away. Thus, most hydro growers – like those responsible for the growroom in this article – use drain-to-waste systems that direct the runoff to sewer drains, never to be seen (or used) again.


The medium used for a particular setup can ultimately be the deciding factor in whether or not the nutrient solution is reused – and it can also determine the type of system that a grower chooses. Hydroponic grow mediums can be very finicky, and which type to use should be the first consideration of any grower when choosing a hydro system. Some hydroponic mediums offer much less stability when it comes to buffering (i.e., protecting) fragile root systems from intense feeding programs.


The easiest and most widely used mediums for new hydro growers are the soilless mixes. Beginner growers can use store-bought mixes such as the Pro-Mix or Sunshine brands, while the most advanced growers tend to buy the essential components and then mix their own concoctions to suit their garden’s needs. These mixtures, whether store-bought or homemade, generally use the same bases: peat moss, sphagnum or coco coir. Additives such as wood chips or lava rocks help create an airy medium so that oxygen can get to the roots. Other additives, such as perlite and vermiculate, not only keep the medium loose, but also retain moisture long after watering to help prevent roots from drying out and plants from getting thirsty between feedings.


Advanced hydro growers often choose soilless mixes because they come as close to real topsoil as possible, with all of the benefits and none of the hazards. Natural earth topsoil often carries insects and diseases, and it may also have high levels of clay or low levels of the nutrients necessary for plant growth. As a result, advanced hydro growers often choose coco coir as their base medium. Coco coir is simply the fibrous insides of coconut shells that have been processed and sterilized. Coco comes in a variety of formats, from longer, stringy fibers to more condensed chips or cubes, to even more finely ground particles and powder. Coco coir is an excellent option because it hits on all three major requirements for a grow medium: It keeps the medium airy, it holds a lot of moisture, and it surrounds and buffers roots systems nearly as well as soil.

Notes on pH, EC and Flushing

While it isn’t necessary for every hydroponic gardener to construct a growroom of this magnitude, it is essential for all levels of hydro growers to understand the complex nuances associated with hydroponic gardening. These aspects include monitoring pH and EC (electrical conductivity) levels, as well as identifying deficiencies that can indicate nutrient lockup (within the root system) or nutrient burn (on a plant’s leaves and stems).


pH is a measure of your water or nutrient solution’s acidity or alkalinity. Solutions with pH levels below neutral (7.0) are acidic, while levels greater than 7.0 are alkaline or basic. Hydroponically grown plants need their solutions to fall between 4.5 and 6.5 for optimum nutrient uptake. If the pH is wrong, all the nutrients are wrong; however, pH levels can be easily adjusted with pH up or pH down solutions. The growroom described in this report was equipped with an automatic pH mini-doser as a security precaution: If the growers missed taking a reading or a high fluctuation occurred, the electronic meter would automatically detect the problem and inject the correct amount of pH up or down into the tank to bring the level back to below 6.5. As an added note, pH measurements should always be taken from the runoff after feedings, as this is a better indication of pH levels in the nutrient solution, medium and root zone.


But why exactly is pH so important. and how does it relate to the EC of nutrient solutions and their uptake by roots? The pH of a nutrient solution is an indication of an electrical molecular battle going on at root level. Nutrients, water, grow medium, air gases and roots all have varying electrical charges, and these charges determine how nutrients are absorbed by the plant’s roots. An EC meter measures this electrical conductivity and gives growers a small idea about what’s going on in their plants’ root zones. EC and ppm (parts per million) meters actually measure the same thing: how fast electrons are moving through a solution. When nutrients (known as salts) are added to pure water, the EC increases (as it also does when the temperature of the solution goes up). However, as the salts increase in water with more nutrient additives, the salts’ EC begins to challenge the roots’ EC for water attraction; and at higher levels of ppm or EC within a nutrient solution, the nutrients will actually begin to steal water from the root systems.


Once these levels reach a high enough point (3,000 ppm or an EC over 4.0), root systems become unable to absorb water or nutrients at their necessary rate, and nutrient lockup begins to set in. This will cause mild to severe deficiencies on the topsides of plants, and if it isn’t identified and corrected quickly, this lockup could kill an entire garden. In every hydroponic system, from flood-and-drain tables to deep-water culture (DWC) buckets, it’s important for growers to not only continually take meter readings, but also to carefully inspect the leaves and stems for signs that there may be a problem down below, including discoloration of leaves, molting, paling or spotting. The leaves may also begin to curl or even wilt.


Using a ppm or EC meter is the best way to catch this problem early and even prevent it. Once signs start showing on the plant’s topside, it will be much more difficult to fix. The only thing a grower can do once lockup sets in at the root zone and the signs become apparent on the plant itself is to start a vigorous flushing program. To do this, reservoirs must be completely emptied, cleaned and filled with pure, neutral water with zero nutrients. Grow mediums must then be completely flushed out periodically (at least twice daily) to remove all impurities and salt buildups left over in the grow medium and root structures. This process can take up to a few days to complete, depending on the severity of the problem.

Final Talley

For those of you keeping score at home, a growroom of this caliber grows approximately 272 grams of excellent indoor cannabis per day given the 56-day flowering period of the Blue Dream strain. Taking into account the fact that these plants all started from clone, as well as the time it takes to root cuttings and vegetate plants – for a total cycle of about 80 days – this growroom yields approximately 190 grams a day. Do that four times a year and life ain’t bad.


But as we know, it isn’t easy, and it’s certainly not for everyone. For starters, significant startup capital is needed to build a dream room like this, not to mention considerable experience and knowledge. And it’s definitely not as simple as outdoor cultivation, where the power of the sun is free and its natural light second to none. But if you’re living in or close to a city where there’s significant market demand for high-quality medical cannabis, a well-constructed and properly maintained hydroponic growroom can be an attractive option if you have what it takes.