Keeping Your Hydroponic System in Great Shape for Growing Marijuana
Hydroponic gardening is an alternative to conventional, soil-based cultivation that frequently makes excellent sense for marijuana growers. This is especially true for those growing in places like Kansas and South Carolina that need to keep their plants indoors and away from prying eyes. Properly set up and maintained, a hydroponic system will be able to provide everything that the roots of marijuana plants normally draw from soil.
That being said, succeeding with hydroponics does require some fairly technical knowledge and specialized attention. Fortunately, most who are interested in this potentially rewarding type of marijuana cultivation find it easy to come up to speed with the basics.
Wicking Reservoir or Drip? Two Common Styles of Hydroponic Systems
There are at least a half-dozen possible ways to provide pot plants with the nutritious solution they need from a hydroponic system. These range from particularly simple but labor-intensive options like hand watering to medium-free “aeroponics” setups that leave roots dangling in the air.
The two most popular options at this point, though, are likely reservoir-style systems that rely on capillary action–or wicking–and drip-based setups:
- Wicking reservoir. Several of the most common hydroponics system designs feature a reservoir that holds relatively large amounts of nutrient solution. That watery resource still needs to be made available to the roots of marijuana plants, though, and there are several ways to do it. Reservoir-based hydroponics systems that rely on capillary action typically see the solution being maintained such that it rises a fraction of the way up inside the growing containers held above it. Either the growing medium within those containers or a wick added for this purpose will then keep the substrate moistened via capillary action.
- Drip-style. The same general arrangement used in a wicking reservoir system can be used as the basis for a pump-equipped drip setup. In this case, a small pump will pull nutrient solution from the reservoir and push it through tubes that allow the liquid to drip steadily into each growing container. It is even possible to set up something of a cross between the two styles such that plants receive a gentle drip of nutrients from above while their roots are allowed to extend into the reservoir.
These two types of hydroponics systems are likely the most accessible and easiest to maintain of all the options. As such, growers who are inexperienced with hydroponics are often advised to start with either one.
Choosing a Medium and Nutrients
One of the advantages of hydroponics is that it does away with unpredictable, potentially contaminated soil in favour of either a regular, largely inert growing medium or nothing at all. Drip- and wicking-style reservoir-based hydroponic systems do need to include a medium, and some of the most popular options today are:
- Most often used for insulation, the artificial material mineral wool, often sold under the brand name “Rockwool,” also makes an excellent growing medium. Although Rockwool needs to be prepared to accept germinated weed seeds by having its pH and electrical conductivity levels adjusted, it is an especially popular choice.
- Coconut fiber. Natural coconut fiber, or “coir,” retains water well and is renewable and reusable. It also has by default a pH that makes it perfect for use as a hydroponic medium when growing marijuana.
- A blend of mineral wool and either coconut coir or polyethylene called “Mapito” delivers most of the benefits of each. While Rockwool is usually sold and used in solid bricks, Mapito is a loose material that requires more careful handling.
- Clay marbles. The kinds of absorbent clay marbles or pebbles often seen in flowerpots can also be used as a medium for reservoir-based hydroponic systems. Also sometimes sold as “hydroton,” these small stones necessarily leave open spaces between them that can aid oxygenation and root extension.
Any of these media can be used to successfully grow marijuana via hydroponics in Florida or anywhere else in the country. Choosing an appropriate nutrient product to add to the system will typically be more important than settling on a particular medium. Some of the issues that need to be accounted for when deciding upon nutrients are:
- Intended use. It will normally be simplest and best to stick to nutrient blends that have been designed specifically for use in hydroponic systems. Experts might ignore this rule, but beginners will be better off heeding the advice on the label.
- Lack of organic ingredients. Organic substances like bat guano and blood meal are found in many nutrient products but should be avoided when growing hydroponically. A hydroponic system will not foster the bacteria needed to break these ingredients down into usable nutrients, as soil would. When organic ingredients get added to a hydroponic reservoir, cloudy fouling will often result.
- Appropriate NPK ratio. The macronutrients found in almost all fertilizers are nitrogen (elemental symbol “N”), phosphorous (“P”), and potassium (“K”). Marijuana plants do best with NPK nutrient ratios of approximately 7:5:5 while developing and about 3:10:10 once they start flowering. As such, it will generally be best to switch to a different nutrient blend after forcing flowering or once auto-flowering begins. Another wrinkle to be aware of is that nutrient absorption rates and availability levels differ between hydroponics and soil-based cultivation. Sticking to nutrient mixes designed specifically for hydroponics will ensure that these issues get accounted for.
Additional nutrients. Marijuana plants also need the macronutrients calcium, magnesium, and sulfur, along with micronutrients like boron, cobalt, and zinc. Some of these are expected to be available in the trace quantities required in soil, so will not always be present in nutrient mixes designed for that style of cultivation. Once again, though, sticking to nutrient blends intended and labelled for hydroponics will do away with this issue.
pH, Electrical Conductivity, and Total Dissolved Solids
Choosing an appropriate style of hydroponics setup, growing medium, and nutrients will always make for a good start. Most of the work needed to successfully grow marijuana using hydroponics, though, comes later on.
In particular, hydroponics growers need to be aware and in control of at least two of three distinct measures at all times. The pH, electrical conductivity (EC), and total dissolved solids (TDS) of the solution in a system all impact the ability of marijuana plants to survive and thrive:
- A measure of the level of hydrogen ions in a solution, pH impacts the ability of useful bacteria to grow and how quickly marijuana plants can mature. A pH of 7 is thought of as “neutral,” with readings below that level being considered acidic and those above it basic. The logarithmic scale used to express pH indicates a tenfold increase in acidity or basicity with each unit of movement away from the starting point. Compared to a solution with a pH of 6, a sample with a pH of 4 would therefore be 100 times as acidic. Hydroponically grown marijuana plants do best with a somewhat-acidic nutrient solution pH in the range of 5.5 to 5.8. At pH levels below 5 or above 7, growth rates will suffer significantly. Significantly larger deviations can cause serious damage to plants.
- Marijuana plants absorb water and nutrients through their roots using simple osmosis. If the nutrient solution made available to a plant is overly heavy with salts, that process becomes less efficient. In extreme cases, an excess of salt can even reverse the osmotic flow, potentially drawing water back out of a plant through its roots. The simplest way to measure the salt level in a nutrient solution is using a meter that calculates the liquid’s electrical conductivity, or “EC.” Nutrient products appropriate for growing cannabis hydroponically tend to feature EC levels from 1.2 to 1.5 millisiemens/centimeter, or mS/cm. Growers should aim to keep the EC of the solution in a system within that range at all times, as well.
- Meters that calculate EC often display the “total dissolved solids” in a solution. This figure, expressed in terms of parts per million, or PPM, can be taken as a supplement to an EC reading or as a way to establish a baseline by measuring the TDS of the water to be used. A TDS reading of below 600 PPM could signal a dearth of nutrients, even where the EC reading seems appropriate. Likewise, a TDS level of above 750 PPM or so might indicate that salts are building up within the nutrient solution excessively.
Sampling, Adjusting, and Rinsing
Of course, it takes more than an understanding of what pH, EC, and TDS signify to put these concepts to use with hydroponics. Following the directions provided with a hydroponics-specific nutrient mix should be enough to get off to a reasonable start but testing and adjustment will be needed thereafter.
Most hydroponic growers set up a regular testing schedule, typically after deciding how to obtain samples. The simplest option is to take a number of nutrient solution samples from evenly spaced parts of a system, and then measure and record the pH and EC or TDS of each.
Once those measurements have been analyzed, the samples can be combined to enable an aggregate reading. That should give an idea as to the overall health of the system, just as individual samples provide windows on particular parts of it. When issues arise with either pH, on the one hand, or EC or TDS, on the other, the following responses will normally be in order:
- If the pH of the system has dropped below 5, adding small amounts of a base like potassium hydroxide can help raise it. Should the pH rise above 6.5 or so before plants have started flowering, diluted nitric acid can be added to push it back down. Later on, diluted phosphoric acid is more often used, with products containing each often being labeled with the developmental stages they are intended for. Always make modest adjustments to pH, wait for the system to stabilize, and then sample and measure again. Otherwise, dangerously large swings can result.
- EC or TDS. EC should normally be maintained between 0.8 and 1.8 mS/cm throughout the growth phase and then dropped to 0.4 and 0.8 mS/cm while plants are flowering. An overly low EC reading is a sign that nutrient levels need to be increased. If EC levels rise too high, adding more water to the system will lower them. Because evaporation removes water from a system but leaves salts behind, EC and TDS readings will tend to climb on their own over time, even when everything is in order. The hardness of the water used in a system, as expressed by its TDS, will also impact the effectiveness of nutrients used to adjust EC. Harder water will take a smaller proportion of the nutrients into solution, requiring larger additions to achieve the same boost to EC.
Regular measurements and indicated adjustments should be used to keep pH, EC, and TDS levels as stable as possible. Flushing or rinsing the growing medium as needed is the other key to keeping conditions within a hydroponic system favorable to growing our regular and feminized cannabis seeds.
Rinsing the medium removes built-up salts and any debris that has accumulated within it, allowing for an essentially fresh start. The system can also be flushed before harvesting to encourage plants to use up nutrients they have stored. While this might reduce yields somewhat, it can improve quality while also setting a hydroponic system up for the next crop. When it comes time to re-order your hydroponic marijuana seeds, we hope that you can take advantage of the great deals on American seeds available at kindseed.com
