Chances are, if you’ve heard anything about growing cannabis, you’ve heard the term “hydroponics”. Though this gardening style is not exclusive to marijuana, it is a popular method for indoor growing of cannabis. Hydroponic literally translates to “water work”. In other words, the cannabis is sprouted and grown entirely without soil. Bathing the roots of the plant in water enhanced with nutrients and offering plenty of oxygen can result in quicker growth than soil-based methods.
Should I Grow Cannabis Hydroponically?
Though hydroponic growing is not difficult, it can be more time consuming than growing in soil because more factors are under the grower’s control, and certain methods can be a bit costly in the beginning. Before deciding to grow any plant hydroponically, we’d recommend researching different hydroponic methods.
Start by reading this article or watching our Hydroponics videos!
Benefits of Hydroponic Gardening
Why should you grow marihuana with hydroponics?
- Often, the plants grow more quickly because the nutrients are delivered directly to the root system, while in soil the roots must actively seek out the necessary nutrients. This reserved energy can instead be expended on growing leaves and buds.
- A perfect balance of the necessary nutrients can greatly shorten the growing time of the cannabis plants. While it is nearly impossible to get this perfect ratio using soil (due to the unknown contents and natural imbalances of the dirt), with a hydroponic system, the gardener has complete control over the nutrients.
- Growing in a hydroponic environment is much more sterile than using soil. Soil can contain unknown components such as bugs and parasites.
- In a pot with soil, the cannabis can become root bound, which can result in slower growth. It is much less likely for plants grown using hydroponics to become root bound.
- It’s fun, and you’ll learn lots!
Drawbacks of Hydroponic Gardening
Though hydroponic growing is an excellent option for some cannabis gardeners, it may not be ideal for everyone.
- Hydroponic growing usually costs a bit more, due to the type of equipment that must be purchased and maintained.
- While most people have planted something in soil at some point, hydroponics has a bit of a learning curve.
- Hydroponic equipment must be cleaned and inspected regularly, and it is more difficult to fix if it is damaged.
- Because all the processes are sped up, any nutrient imbalances or other problems will be sped up as well; this can result in a damaged cannabis crop before the gardener realizes something is wrong.
How to Grow with Hydroponics
Hydroponic System Lighting
Hydroponics require the same lighting set-up as soil-grown cannabis. Though it may be more practical to use the same light bulbs throughout the growing period, some gardeners find it useful to use a Metal Halide bulb during the vegetative stage, and a High Pressure Sodium (HPS) lamp during the flowering stage. Alternately, some indoor gardeners are switching to LED.
Once the grow room has been set up, germinated cannabis seeds can be placed into their pots or buckets. To learn more, see our article all about Germination.
Hydroponic Growing Mediums
The sprouted seeds are placed root down onto the growing medium, which is used in lieu soil. There are a number of mediums available to hydroponic gardeners.
- Rockwool can be a pricier option, but can be reused for multiple cannabis crops. It has a naturally alkaline pH, and may need to be neutralized prior to use, but this is a fairly simple task.
- Lava rocks are another popular option. Mediums that have been treated in any way should be avoided when growing cannabis – they can throw off the careful balance of nutrients.
Choosing The Right Pot for Your Pot
Though there is little danger of hydroponic plants becoming root bound, a larger pot will encourage plants to grow larger, and therefore produce larger buds. Likewise, using a smaller pot can keep plants at a size more manageable for a small grow room.
The faster the hydroponic medium drains, the more vital oxygen the roots of the cannabis plants will get, but fast drainage also means more frequent watering. If you are using a hydroponic system that involves soaking the roots (as opposed to misting), the medium should be about three-quarters submerged when the nutrient-water mixture reaches its highest point.
Read More: Growing cannabis indoors using soil
Read More: Growing cannabis outdoors in the garden
Different Hydroponic Systems
Below the general umbrella of Hydroponics, there are various systems. Though each system delivers necessary nutrients to the cannabis through water alone, they all differ slightly in the equipment, set-up, and method of administering the water. The three systems outlined below are popular for cannabis gardeners.
Ebb and Flow System
This system uses a pump to push water through the reservoir that runs below the plants. The water rushes over the roots of the cannabis plant before draining back out. This process is repeated every 20 minutes or so.
The automated watering process makes the Ebb and Flow system a bit pricier than others, and since the same water is being flooded over many plants, an infection or parasite can damage the whole crop.
The lack of any stagnant water is the biggest benefit of this hydroponic system. As well, the water that drains away can be used to water other house plants.
Aeroponics
As the name implies, the aeroponic system of hydroponic growing uses air to water the cannabis plants or, more specifically, mist. The plants are suspended within a large, tented area with nearly 100% humidity. The root system dangles below the plant in a sealed section. Nutrient-rich water is misted into this area at regular intervals.
Aeroponics is best for larger operations, since the set-up is quite extensive. One potential downside of this system is that large roots of some cannabis plants can overtake smaller ones, resulting in an uneven distribution of the nutrient mist.
Deep Water Culture (DWC)
In a Deep Water Culture hydroponic system, the cannabis roots are left underwater, in a lightproof container to prevent algae or mold growth, while the plant stretches above. The roots absorb the nutrients from their constant submersion, and get their oxygen from an airstone (also called an air rock), which is placed in the water as well. Airstones naturally release oxygen into the water in the form of bubbles.
Stagnant water is the biggest problem with this system, so the water must be checked and changed regularly. Too little oxygen in the water can also kill the plants; too many airstones is better than too few – it is almost impossible to over-oxygenate the water.
The Nutrient Mixture
There are three primary nutrients required as fertilizer for growing plants – cannabis or any other: nitrogen, phosphorous, and potassium. Other nutrients, including calcium, magnesium, and sulfur, are needed in smaller quantities.
In soil-based growing, water dissolves the nutrients naturally found in the potting soil, and the cannabis roots absorb this water. In hydroponics, a powder or salt mixture of the essential nutrients is added to the water as an infusion.
Correct Measurements of Nutrients
By mixing nutrients with water, hydroponic gardeners are able to control exactly how much of each nutrient the cannabis receives. If necessary, ratios can be based on the properties of each nutrient: nitrogen stimulates healthy leaves, phosphorous builds hardy roots, and potassium promotes robust growth.
Nutrients must be added to the water with care. Too much fertilizer can kill cannabis plants, while too little will result in a longer grow time, but not cause any lasting damage. In other words, it is best to err on the side of too few nutrients.
The Water
The nutrient-water combination used in hydroponic growing should be tested daily to ensure the mixture remains at its ideal acidic pH. Because all the processes are accelerated, an overly alkaline mixture can cause a lot of damage to the cannabis plants, very quickly. It is easy to check acidity with a store-bought test, and products are available which can alter the pH in either direction. The water, which should be between 18 and 27 degrees Celsius, should have a pH of just above or just below 6.
The water level in a hydroponic system will decrease as the roots of the cannabis plants absorb the dissolved nutrients, and this reservoir will need to be regularly topped up. Some gardeners include nutrients in this replenishing water while others use pure water to top up, and nutrient-rich water after a complete drain. Regardless of any additives, tap water used in hydroponics should always be allowed to sit a few days before use.
How Long Should I Wait Between Watering?
Just like any other plant, different strains of cannabis require different lengths of time between watering. Some strains may need to be damp at all times, while others may do better when the root system is left to dry slightly between waterings. The best method for a specific strain can be determined by some careful experimentation, or by speaking to other hydroponic growers of the same strain.
Some hydroponic systems use pumps and other equipment to facilitate an automated watering process. However, for those new to hydroponics, and even the more advanced who wish to have greater control, hand-watering the cannabis plants is the best way to control what and how much the cannabis plants are receiving.
Purging the Hydroponic System
Every two weeks or so, the entire reservoir should be drained and cleaned well before new nutrient-rich water is added to the hydroponic system.
