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Best Hydroponic Nutrients for Marijuana: The Dos and Don’ts


Many cannabis growers choose hydroponic systems for personal or commercial growing. Although this technique requires some knowledge, there are many advantages of growing cannabis hydroponically. Selecting the best hydroponic nutrients for marijuana is an essential step of a successful harvest, but many other factors can affect your yield. In this article, we will address not only the most essential marijuana hydroponic nutrients, but we will also talk about growing marijuana hydroponically, step by step.

What is hydroponics, and why grow cannabis hydroponically?

A hydroponic plant is any plant grown without soil. The most common media used for hydroponic systems include hydrotons (clay pebbles), rockwool, gravel, perlite, coco coir mix (made from coconut fiber), and many others. There is a wide variety of hydroponic systems that can be adapted to any grow room or tent, depending on the size, height, budget, and other factors.

Cannabis plants thrive under highly controlled environments. This means that the more factors you can have control over, the best you can maximize your plants’ yield. And hydroponic systems are plentiful in the way they let you control your growing process. The first advantage is that you can have a highly regulated feeding and watering schedule using a timer with pumps, hoses, and reservoirs. Besides, you can also have control over the feeding using exact mixtures of nutrients in the water.

Growing in soil is often a grower’s first choice; however, many factors can be hard to control. Soils have variable organic matter, mineral, and chemical concentrations, as well as unwanted bacteria and insects. Because you can handle most of the variables and allow the plants to grow a robust root system, hydroponic systems can help you reach impressively high yields in shorter grow cycles when compared to soil.

What are the best hydroponic nutrients for marijuana?

Like most of the plants we know, the essential macronutrients a cannabis plant needs in order to grow are nitrogen (N), phosphorus (P), and potassium (K). All macronutrients brands will have a sequence of three numbers in their packages. This stands for the concentration of each ingredient: N-P-K. Like other plants, cannabis will also require different amounts of each of these macronutrients depending on the growth cycle stage. 

In a hydroponic setting, you must ensure that all your nutrients are specific for hydroponic. This will also mean that there are no organic ingredients, only minerals. This measure is crucial because organic matter can cause bacteria to grow in your reservoir, which can be harmful. By ensuring that all marijuana hydroponic nutrients come in chemical form, this will no longer be an issue.

Marijuana Hydroponic Nutrients: Vegetative Stage

If your cannabis plant is in the seedling stage, you can use root boosters or seedling nutrients. You can also use the vegetative formula, but it must be diluted to 1/5 of the dose. If you purchased a cannabis clone, then the plant is in the vegetative stage because it is already an adult. When in this stage, your plant needs nutrients to grow its root system as well as strengthen stems and leaves. Nutrients for the vegetative stage must be high in hydrogen and potassium and have medium levels of phosphorus. Make sure you use nutrients that are clearly labeled as “grow”.

Marijuana Hydroponic Nutrients: Flowering Stage

Once your plant starts to show its first buds, the flowering stage has begun. At this point, besides changing the light schedule, you should also start using “bloom” nutrients. Watch out for hermaphrodite or male cannabis plants and remove them from your tent or room. The nutrients for the flowering stage should have high levels of potassium and phosphorus, and low nitrogen. The ratio is different because now, instead of growing, the plant is channeling its energy into blooming its buds. Phosphorus will help your plant produce plenty of buds, and potassium will help ensure those buds are bigger and juicier.

Most brands of nutrients will sell products with recommended dosages and feeding schedules, but you must follow with precaution. Manufacturers usually recommend high dosages, so, to play it safe and avoid overfeeding, dilute it to a third or half of the recommended. If feeling unsure, you can learn more details about the growth cycles in our marijuana growth guide.

Although there is a huge variety of brands out there, many growers learn through experience that yields tend to vary, not so much because of the nutrient’s ratio but more because of other factors such as light, temperature, and pH. In short, don’t fret over choosing the right brand with a perfect ratio: just make sure you select the right nutrients for your setting (chemical nutrients for hydroponic systems) and stage of the growing cycle (grow or bloom nutrients).

Pro tip: A widespread beginner’s mistake is overfeeding your plants. Be on the safe side and always go for a smaller dosage, feeding every third or second watering. Even if a plant is underfed, it will have a better yield than an overfed plant.

Growing marijuana hydroponically: step by step and most common systems

Hydroponic systems are very diverse. There are various methods for all types of budgets, spaces, and even the number of plants. We will focus on three of these approaches: deep water culture, ebb & flow, and drip system.

Deep water culture

This hydroponic system consists of a container with a water solution and an air pump connected to an air stone that provides constant oxygen to the plant’s roots. The plant should be placed inside a net or fabric pot, which sits on top of a bucket with a nutrient bath that’s continuously supplied with oxygen. This system’s main advantage is that plants grow a massive root system, leading to impressive yields. 

You can have a simple DWC system with a single bucket for each plant, multiple buckets connected to a bigger one, or large trays. Although this can be complex and expensive, it’s an excellent option for growers with limited space, low ceilings, or very few plants, because you’ll maximize their yield. 

For any growers using this system, you should have extra air and water pumps in place and ready to use. If you risk interrupting the supply of oxygen for over 48 hours, your plants will die. Having said this, you should also pump air from outside of your grow room or tent to avoid high concentrations of CO2. Cannabis plants grown in DWC systems will not adapt if you try to transplant them into a soil media – their roots are not used to it. This system is for an advanced grower who can recognize plant problems quickly.

Ebb and Flow

Ebb and flow, also known as flood and drain, is considered a reliable method and is used by many commercial growers. In an ebb and flow system, plants are put on a tray suspended over a reservoir and connected via a water pump. The pump will send nutrient-rich water and flood the tray in a set time. A couple of minutes later, the pump will turn off and drain the water back to the reservoir. 

Many beginners love this method because it is easy to set up, requires less maintenance, and it’s not difficult to notice if all the plants are getting access to the nutrients they need. However, ebb and flow can become expensive because it uses up a lot of water and nutrients. So you’ll have to weigh up costs vs. benefits to make the best decision for you. If you do choose this system, make sure you have a high ceiling! The plants will be above a reservoir, so the trays need to be high. Otherwise, once plants start growing, they could get too close to the lights and suffer from light burn or heat stress.

Drip System 

Just like with ebb and flow, in the drip system your plants will need to be above a reservoir – so make sure you have enough room for their growth. To create this system, connect a larger pump from a reservoir to a hose with branches and smaller hoses. This will then link via an outlet to each plant, feeding it with water and nutrients. The water goes through each plant and returns to the reservoir. It is slightly more complex than the other systems and has more components, as you’ll need to have one outlet for each of your plants. So the more plants you have, the more complicated it gets.

You’ll also need to routinely check each of the hoses because they’ll be a buildup of residues from the nutrient-rich water. So every time you’re starting a new grow, it’s essential to flush the hoses with a cleaning solution to avoid this buildup. Inspect the tubes frequently and avoid organic nutrients because those are prone to clog the tubes. On the good side, this system is relatively easy to set up and consumes much less water than the others.

Key takeaways of growing cannabis hydroponically

Be careful not to overfeed:

When talking about marijuana hydroponic nutrients, less is more. Dealing with a plant that’s been overfed with too many nutrients is much worse than dealing with and underfed plant. So don’t be tempted to cram in too much.

Water temperature and pH are more important than anything:

Controlling the water temperature and pH is crucial to avoid root diseases or rot. The temperatures must be controlled between 62-68 F, and the pH must always be between 5.5 and 6.5. This is even more important than marijuana hydroponic nutrients because even if you have get the nutrients right, not paying attention to such factors can ruin your crop.

Keep an eye out for nutrition imbalance signs:

drooping or yellow leaves before the final flowering stage or irregular leaves can be a sign of nutrition issues. Double-check the temperature, airflow, light levels, flush your hydroponic system with neutral pH water, and then start again with nutrients diluted to a third or half of the dose.

Do you want to start your hydroponic marijuana grow on the right foot? Follow our Cannabis News section, we update it weekly with the best tips for growers.

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