How to grow cannabis with a DWC system

Growing DWC cannabis is a rewarding, and surprisingly simple, process. Though the setup itself is a little more complex, costs are minimal—little more than a traditional soil grow. Despite a slightly higher difficulty level than soil, anybody willing to give DWC the time should find themselves successfully growing supercharged bud in no time!

What Is a Deep Water Culture (DWC) System?

A deep water culture (DWC) system suspends the cannabis plant’s (or any plant’s) root system in a highly oxygenated, nutrient-rich solution. It is considered the simplest form of hydroponic growing. Despite its simplicity—even being suited to total beginners—it is known to be highly effective, and produces cannabis plants with some exceptional yields.

While it is still fairly technical, and involves some moving parts, deep water culture is fundamentally a simple system that offers a lot in terms of reward.

What Are the Advantages of Deep Water Culture (DWC)?

There are numerous benefits to DWC, and hydroponic growing in general. This is not only true for cannabis, but for many other plants as well. The major benefits of DWC cannabis are:

• Accelerated growth—get your bumper crop in record time!
• DWC systems are very user-friendly—a perfect starting point on a hydroponic voyage
• Moderate maintenance requirements
• Reduced risk of root rot and diseases
• Relatively cheap
• Simple and precise administration of nutrients

What Are the Disadvantages of Deep Water Culture (DWC)?

Of course, it’s not all perfect. There are some good reasons why many cannabis growers just stick to more traditional, soil-based growing.

• Requires a specific and hard-to-maintain water temperature (20°C)
• The water requires constant oxygenation, otherwise roots can rot and algae can grow
• While administering nutrients is simple, maintaining good levels can be hard, and failure to do so is much more damaging in a hydroponic system

That being said, these issues can be easily avoided with careful management and maintenance. But, as deep water culture is a less-forgiving method than soil, it becomes much harder to make things right after they have already gone wrong.

In other words, deep water culture is a method suited to those with the time and energy to dedicate to it.

How Many Cannabis Plants Can You Grow With DWC?

It depends how big your space is, and how much money you’re willing to throw at it. However, the bigger the DWC system, the more liable it is to go wrong. So, to begin, perhaps just experiment with a single reservoir containing a single cannabis plant, powered by a single air pump. Once you get the hang of it, you can then extend your empire.

How To Make a Deep Water Culture System at Home

So long as you’re patient and careful, setting up a DWC system at home shouldn’t cause you too much trouble. But, as already mentioned, it is something that does require constant care. It’s not about throwing a few seeds in a pot and seeing what happens a few months later.

For those who like visual instructions, this video provides a simple and effective rundown on how to start a DWC.

What Do You Need for a DWC Cannabis System?

There are some essential bits of kit you will need to get started making your DWC system. Nothing is very expensive or hard to come by, so you should have no problem sourcing it.

In terms of growing cannabis in a DWC, the easiest option is to first germinate seeds in soil, and then place the seedlings in the hydro system. This is because germinating seeds in a DWC system can be tricky. Likewise, using cuttings can be very difficult without the proper know-how. Without soil to anchor into, the plant can struggle to begin producing roots.

For your DWC cannabis grow you’ll need:

• Storage container or bucket
• Net pots
• Air pump with air stone
• Hard water liquid nutrients (A & B)
• pH down
• pH meter
• Measuring beaker
• Pipettes
• Hole saw with arbor
• Drill
• Cannabis seedling of choice

Steps

The method is fairly simple, and doesn’t contain any overly complex steps. Nonetheless, it is important to ensure each step is done well, as any problems later down the line will cost you much more energy than setting them right now.

Step 1: Choose Your Container

A bucket or box will do. You don’t need anything fancy. But there are a few criteria your chosen container needs to meet in order to be effective for deep water culture. It must be opaque, as any light will encourage the growth of algae. Deeper is better, too. A larger volume of water means a better spread of nutrients, and makes dangerous fluctuations less likely.

The container will also need a lid, for the cannabis plant to sit in.

Step 2: Make Holes

Now you will need to drill holes in the lid. This is where the hole saw comes in handy. Your net pots will sit below the hole, whereas the rest of the cannabis plant will rise up through it. The size of your container will dictate how many holes (plants) you can fit. Remember, they can grow quite a lot, and wide! So leave plenty of space between the holes. This is why we suggest beginning with a single plant until you understand the process.

Step 3: Attach the Air Pump

If you can, get an air pump with a check valve. This means that when it is switched off, it won’t suck water back into itself. If you do not have a check valve, then the air pump can be kept above the water level.

Attach the end of the air pump to an air stone; this will ensure the air being pumped through is pure. The air pump itself must sit outside the reservoir, with only the end and the air stone being submerged.

Step 4: Fill It Up!

This one’s simple; just fill your reservoir with water. You only need to leave a 1 or 2cm space at the top. You should also note that, over time, the water level will drop, as cannabis plants need to drink, and some will evaporate. Therefore, you will need to top it up from time to time.

Step 5: Add Nutrients and Adjust pH

Now you need to make the water hospitable for the plants.

You can buy hydroponic-specific feeds, and this is recommended. Find one specifically designed for cannabis, too.

In terms of pH, around 6.0 is good for hydroponic growing—slightly lower than a soil grow. Most water is slightly alkaline (7.0) or above, so it will need to be acidified. You can buy pH down solutions, which are basically phosphoric acid. Drop this bit by bit with a pipette until it reaches the right level.

Concerning both nutrients and pH, check them regularly as they can be temperamental, and unchecked fluctuations can be fatal to your plants!

Step 6: Put Your Seedlings In

Now you want to get the actual plants in. We advise you to use seedlings (if not, there is more information below), as these will take most easily. Using rockwool, or some other hydroponic medium (clay pellets, coco, etc.), place your seedlings in the net pots—which will be suspended in the water—and just make sure they have adequate nutrients, pH, and oxygen.

How To Start a DWC With Cannabis Seeds

You can place cannabis seeds into the rockwool plug, and germinate directly in your DWC. It is simple, but not necessarily easy. Seedlings are incredibly delicate at this stage and can die if anything goes wrong. So, unless you are confident you can maintain an almost perfect environment, germinate them outside of your DWC system.

How To Grow Cannabis Cuttings With a DWC

Growing clones from cuttings is sometimes desirable. If one plant was just perfect, you may want to replicate it.

To do this in a deep water culture system, it will need artificial support, as it does not have soil to anchor into. You’ll need a foam collar; cylinders of foam with a slit, into which you’ll slide your cutting. This is then placed into a net pot. Make sure to cover your plant with something (e.g. a plastic bottle with air holes) to stop the cutting from drying out before it has proper roots.

How To Maintain a Deep Water Culture System for Cannabis

To make sure everything goes smoothly with your DWC cannabis grow-op, there are a few simple maintenance practices you must abide by:

• Ensure the temperature stays the same.

• Change the water entirely every 14–21 days. This stops other things from growing in there.

• Top up the water/nutrient solution! Especially when plants are young. The root system should always be in contact with water. When you top it up, the nutrient balance will change. So know how much fresh water you added, and adjust nutrients and pH level accordingly.

If you are going to reuse the same system for multiple crops, then thorough cleaning will be required in between grows, as will proper cleaning of the air pump.

Regularly Check the pH and EC

Check on nutrients and pH! Prepare to become almost obsessed with this, as fluctuations are common and not good. Invest in an EC (for nutrients) and pH pen. These will make life much easier.

Cannabis plants need an acidic environment to thrive; in a hydroponic system, about 6.0 should do. The EC level tells you the electroconductivity of the nutrient solution. This is enhanced by salts and silica. A good EC level allows proper uptake of nutrients in the roots. Make sure it is optimised.

Provide the Correct Amounts of Nutrients

Speaking of the nutrient solution, your feed should offer you guidance based on the stage of development. However, as a general rule, cannabis plants want a 3:1:1 ratio of nitrogen, phosphorus, and potassium during the vegetative stage, and a 1:3:2 NPK ratio during the flowering stage.

Based on the product instructions, it can be advisable to begin with half the recommended amount and then build up from there. When your plants are young, they won’t need much. And (especially in a hydroponic system), it is much easier to add nutrients than remove them.

What Are the Best Nutrients for DWC?

There are some factors that will determine how good your feed is for a DWC system, such as:

• Designed specifically for hydroponics
• No organic matter—only minerals
• Mineral nutrients are "chelated" (easier for plants to absorb at a greater range of pH levels)
• Rich in sources of micronutrients; these replace what would otherwise be found in soil
• Optimal NPK ratio for stage of development (see above)

Keep the Solution Around 20°C

At high temperatures, the amount of oxygen in the water will decrease. This can quickly lead to oxygen deprivation, which will stunt your plants’ growth, or kill them.

How To Cool a Hydroponic Reservoir?

As your plants will be under powerful, hot lights, it can be difficult to keep the water/nutrient solution cool enough. But there are a few ways to do this:

• Buy a cooler (expensive): These pump refrigerated air into your DWC as necessary, maintaining an optimal temperature.

• Insulate: As the heat will be coming from the outside, paint your container white or wrap it in something reflective. Alternatively, put it beneath a secondary, insulative surface, through which only your plants show.

Work Clean and Replace the Nutrient Solution Regularly

This way, you will not get buildups in the nutrient solution. The most common are algae, but other things can grow too. The problems these can cause range from messing up the oxygen and nutrient levels to root rot and killing your plants. By maintaining cleanliness and refreshing your nutrient solution, you mitigate this risk.

How Do I Refresh the Solution?

A liquid transfer pump is a relatively inexpensive and simple way to remove the water from your container. Otherwise, you will need to remove your plants and store them somewhere where the root system won’t get damaged while you manually empty your container. While this is fairly simple, it can go wrong, and, for the sake of your whole crop, it’s best to avoid it.

How Often Do I Have To Refresh the Solution?

Every 14 to 21 days should suffice to keep the water/nutrient solution clean. Though, if you notice anything growing, don’t wait; refresh it immediately.

Regularly Check Your Equipment

Keep an eye on your equipment. You don’t want light leaking into the water, and, if your air pump breaks down and you don’t notice, the whole project could come to an end. Regular and simple maintenance will save you from catastrophe down the line!

How To Flush DWC Cannabis Plants

There’s an ongoing debate about whether flushing actually improves the quality of a crop. Many cannabis growers like to do it, in case it does. With a DWC system it’s fairly simple. About a week before you plan to harvest, remove all the nutrient solution, and then refill your reservoir with fresh water. Continue to do this every 4–12 hours until you get a stable EC reading of 0.1–0.2 μS/cm above your baseline.

Best Cannabis Strains for DWC

You want robust strains when growing cannabis in a DWC setup, as fluctuations will do greater damage to delicate ones. Though you no doubt have your own favourites, and may well already have a specific cultivar in mind, we’ve made a list of three of our favourite cannabis strains for a DWC hydroponic system.

Amnesia Haze

Amnesia Haze needs little introduction. This sativa-dominant powerhouse has highly stimulating, almost psychedelic effects. These plants can really flourish too, so allow them lots of space as sativas love to stretch. Just make sure you err on the side of underfeeding, rather than overfeeding, as it doesn’t like nutrient toxicity. The flowering time can be long, as much as 12–13 weeks. Therefore, this plant should be grown by those with some patience. Rest assured, though, it will reward you well.

Power Plant

Power Plant is bred from a South African landrace and is quite special. It too is sativa and has highly uplifting, energising effects. Unlike Amnesia Haze, it grows fast and generously. It will be ready to harvest within 8 weeks of flowering. This rapid growth means you'll need to keep a close eye on the nutrient solution, as it will guzzle it quickly and demand more! Despite its greedy nature, what you get at the end is so generous that it has even won awards for this very reason.

Gorilla Glue

Another very famous strain, Gorilla Glue has been around for some time and shows no signs of going anywhere. It’s indica dominant and, as the name suggests, has such abundant resin production that it’s almost like glue. This makes it perfect for extractions and concentrates. THC levels can push up to 26%, and its descendants can go over 30%—it is incredibly strong. So, go steady or it could have you floored! In terms of growing, it takes about 8–9 weeks to flower and comes with generous yields.

Growing Cannabis Using Deep Water Culture: Suited for Beginners and the Experienced

Don’t be afraid to use deep water culture for growing cannabis; it really is very simple. That’s not to say it’s easy, though. The main thing that’s likely to go wrong is underestimating how much attention it needs. However, if you’re willing to commit to it, your DWC system will offer you massive, fast rewards. So, what are you waiting for? Give it a try and expand your growing expertise with DWC!