How to grow cannabis in deep water culture (DWC)

Growing cannabis in DWC system

A DWC cannabis grow comes in many different styles and adaptations. However the common theme is that the roots are immersed in a bath of nutrients at an optimum pH, often around pH 5.8. Normally cannabis roots left in water/nutrients would eventually rot.

But the presence of bubbling air (e.g. from a DWC air stone, connected to an external air pump) provides the roots the oxygen they need to grow with great vigour.

The container is often simply a deep bucket (hence the name, DWC) which is often black in colour. The absence of light keeps dreaded slime and algae to a minimum. One plant can comfortably fill the typical 15-20 litre DWC bucket full of cannabis roots by the end of the grow. A healthy root ball is a huge white mass of roots.

The benefits of growing cannabis with DWC

The main attractions of growing DWC cannabis are the fast growth rates and huge yields that are potentially on offer when DWC is done well. For those that delight in the joy of growing their own cannabis, there is an undeniable satisfaction that comes from seeing a successful DWC grow really push the cannabis plant right to it’s limits.

Growing in a DWC cannabis system isn’t for everyone. But for those that do it well, dry yields of several hundred grams per plant are quite routine. Deep water culture cannabis growing pushes hydroponics (soil-free) cultivation to its limits. As such, it’s the ultimate thrill and ultimate challenge for many indoor growers. For those that truly enjoy their cannabis cultivation there are few more satisfying feelings than seeing a crop grow from seed to harvest. When you harvest your first DWC monster the joy and satisfaction will be remembered forever.

But for someone that has only grown in soil before there are some undeniable added new complexities to consider. You will need a, perhaps slightly noisy, air pump to feed the DWC air stone and you may need to discover the joy of owning and calibrating pH and EC meters for the first time.

Nutrient management in DWC cannabis growing

Above the root-zone the plant grows normally, though with enhanced speed and yield thanks to the optimised conditions in the root area. The nutrient bath will need replacing frequently, especially as the plants mature. As with other grow methods, the nutrients tend to slowly increase in strength as the plant develops.

Many serious growers change the nutrient bath at fixed schedules, often weekly. You may be able to leave your nutrient bath 1-2 weeks between changes in veg. But in bloom, with hungry plants you should aim for complete weekly nutrient bath changes at a minimum. Pro growers may change baths even more frequently than that. They will check their baths once or twice a day in late bloom, topping up with nutrients.

The most obsessive DWC cannabis growers change the water daily towards the end of bloom, though this would be considered excessive by many. However, one primary reason why growers like to keep a fresh bath is because the cannabis roots may not use up all the nutrients and NPK minerals in your DWC nutrient line up at exactly the same rate. That means your nutrient bath could suffer an unhealthy accumulation of certain minerals. This can slow down the uptake of other nutrients. The result is a plant that struggles to grow with the nutrition it needs.

Deep water culture cannabis growing. Once mastered, it’s a game changer.

There is no point cutting corners when growing cannabis with DWC. One of the main reasons to grow cannabis with DWC are the potential yields on offer. For that reason, it makes no sense to choose a high-yield/high-maintenance method such as DWC and then try to cut corners. If DWC is worth doing, it’s worth doing well.

DWC NPK charts for cannabis nutrient recommendations are supplied by the nutrient supplier. Careful DWC cannabis growers tend to err on the side of dilute nutrients rather than risk burning the cannabis roots with over-strong nutrient concentrations. DWC allows your plants to grow faster when set up correctly. However, if you prepare your nutrients incorrectly, you will see problems develop very quickly.

By the time most growers have reached the point of trying a DWC cannabis grow, they have already gained a good understanding of how the cannabis plant grows and how to manage/control the nutrients.Nutrient concentration is measured with the usual E.C. (electrical conductivity) meters, often on a daily basis. So is pH.

The grower needs to be able to understand plant nutritional needs at each stage of it’s development. This is something that comes through experience, and through reading signs on the cannabis leaves and the general plant health/appearance.

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Understanding and using cannabis leaves

Best grow material for DWC cannabis growing

DWC cannabis growing is done simply in a bath of nutrients with air bubbling through it. There is no grow medium, other than a small net of pebbles supporting e.g. a cube of fibre glass used for the cannabis seed to germinate in. Other than that there is just a light-tight bath/container for the cannabis roots. By keeping the nutrient bath dark it starves algae and unhelpful bacteria of the energy they need to thrive. With deep water culture the cannabis roots grow explosively.

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Best DWC environmental factors for cannabis

When growing cannabis with the DWC technique you need to consider both the environment provided at root zone as well as the environment provided for the growth and bloom of the plant. The best DWC environmental parameters for cannabis growing ensure explosive root growth in the bubbling nutrient solution is matched with good light/humidity/temperature levels for the plant to grow in.

The roots benefit from a generous level of air bubbles streaming through them. Many pro growers use heavier duty air pumps than those that come with the lower cost DWC systems. Some of the low cost, low-volume pumps can only pump 2-3 litres of air per minute through your air stone.

Expert DWC cannabis growers often like to have 20-30 litres of air per minute going through the air stone underneath their plant, or more. This creates a real ‘fizz’ in the nutrient solution, cannabis roots love this extra aeration. As well as DWC air stones there are DWC hoses. These are coiled, perforated hoses that can pour out colossal air volumes for those that like air pumps with maximum capacity.

This creates a real ‘fizz’ in the nutrient solution, cannabis roots love this extra aeration. As well as DWC air stones there are DWC hoses. These are coiled, perforated hoses that can pour out colossal air volumes for those that like air pumps with maximum capacity.

These higher volumes of air per minute through the root ball encourage faster root growth, but air pumps do create a certain amount of noise. That’s something to consider if you are e.g. a bedroom grower. Maintaining a fresh bath with regular changes is key to a successful grow. As is maintaining right temperatures, and nutrient levels.

Humidity for DWC cannabis

Some experienced DWC weed growers like to keep humidity levels a little lower than they might with other grow methods. That’s because the blooms can get particularly heavy with DWC, risking mould or bud rot. Keeping humidity around or below 50% with a de-humidifier in late bloom is recommended for DWC cannabis growers.

Base nutrients you’ll need for a DWC cannabis home grow

A quick trip to your local grow shop can leave the average DWC grower feeling bewildered with choice. You may prefer to keep things simple, especially to begin with and stick to the minimum number of base veg nutrients and the minimum amount of options when it comes to bloom.

As your experience grows you can extend the range of your nutrient line up beyond the standard NPK options. But it’s a good idea to do this steadily. If you do encounter nutrient deficiencies/issues with your plants, one useful DWC tip is that it can be easier to resolve the problem with a fresh bath made from a minimum number of ingredients.

Cannabis deep water culture step-by-step guide

How to grow DWC cannabis? There are many different variations on the theme of DWC cannabis growing. From single plants grown in a simple DWC bucket. To multiple plants grown together in a more sophisticated system with professional plumbed pipes recirculating the nutrients.

Do your best to optimise your own DWC hydroponic grow so it delivers well for you in your own grow space. Some people use DWC to maximise their SCROG grow. Others like to allow the DWC plant to grow naturally and they will support branches as harvest approaches. There are few ways to grow heavier harvests from a cannabis seed than DWC.

Step 1: Setting up your DWC system

How to germinate cannabis seeds for DWC? Just use the same cannabis seed germination techniques as usual. Normally the cannabis seeds are germinated in a fibre glass cube, or similar. When the seedling has emerged it can be placed into the support net of the DWC system, perhaps nestled in some clay pebbles for extra support. The roots will be too small to reach down to the nutrient solution so you will need to top feed for a few days by hand.

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Step 2: Vegetative grow in deep water culture

As the cannabis seedlings turn into small plants the roots will start to grow more rapidly and will reach down into the nutrient solution. Nutrient concentrations will be low in order that the delicate young roots don’t suffer root burn. The observant grower will notice that the cannabis plants will grow quickly, perhaps far faster than would have been possible in soil. A ph level of around 5.8 for vegging cannabis in DWC is typical.

Step 3: Training your cannabis plants in DWC

Many growing in SCROG find that DWC is an ideal accompaniment. Both DWC and SCROG training help push the plant to the limits, allowing yields of several hundred grams per plant when grown from an autoflower seed or a feminised cannabis seed.

If you don’t want the complexity of a SCROG grow you may find that some simple LST (low stress training) tying of branches can help keep an even canopy and maximise yields.

Step 4: Trimming and removing leaves in DWC

Personal choice plays a role when it comes to attitudes to trimming and removing leaves during DWC. Many DWC cannabis growers feel that leaf removal is essential in order to allow light penetration to bloom sites. DWC tends to produce ample, lush tropical growth. Many DWC growers feel that the plants are tough enough to withstand some essential defoliation so long as it is opening up bud sites to more light.

Step 5: Flowering cannabis in deep water culture

Nutrient control during bloom is one of the keys to success with deep water culture hydroponic cannabis growing. With a cannabis DWC setup, water level needs to be closely monitored. The plants may drink several litres of liquid per day near harvest, so you will need to monitor nutrient levels closely and top up regularly. Remember that the minerals may not all be used up at the same rate. So to keep a healthy nutrient bath, don’t hesitate to make regular fresh nutrient solutions for your plants.

If you grow your autoflower seeds and feminised seeds well you can end up with monster DWC plants. These can be top heavy and blooms may need support. If you spot any unusual ‘bad’ aromas from the roots or nutrients, refresh the nutrient solution quickly and consider some additives to help reduce bacterial activity. Flushing cannabis in DWC is easy, just use pure water.

Step 6: Harvesting cannabis from deep water culture

If all has gone to plan your cannabis plants should be generously proportioned at harvest with plenty of frosty buds. Harvesting can be a delicate process, you want to remove and trim each branch without collapsing the whole plant. The whole process can take several hours and gloves are always recommended.

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Deep water culture cannabis pros and cons

Those that love deep water culture cannabis growing wouldn’t grow any other way. They would acknowledge the extra demands that DWC places on growers, but would argue passionately that this price is surely worth paying for the unique yields that are on offer.

Whether DWC is right for you personally depends on your attitude to a new challenge and a little bit of complexity. Growing cannabis with a DWC system wouldn’t be recommended for a first time grower. But for the ambitious grower that has grasped the basics and doesn’t mind a little extra effort, DWC can change the way you grow cannabis forever. Imagine if you could routinely achieve 100-200 grams++ of dry bud from each plant you grow.

DWC attracts it’s own army of fans who are happy to share their own advice. A quick check on the online grow forums will provide plenty of deep water culture cannabis tips. Online DWC cannabis grow journals can be a useful help to the less experienced grower.

Pros:

• DWC is perhaps the fastest way to grow cannabis
• Yields can easily be several hundred grams per plant
• You can push your favourite cannabis genetics to their limits

Cons:

• You will need to manage a more technically complex system compared to soil growing.
• Despite the claims that DWC is easy, it does require more effort and use of pH/EC metres with associated calibration, etc.
• You may be a successful soil or coco fibre grower that struggles to adapt to DWC. DWC has remarkable benefits but not everyone can adapt to the new ways of working which DWC presents.

Growing autoflowering strains in deep water culture

You can grow autoflowering seeds or traditional photoperiod feminised cannabis seeds in DWC. Autoflower seeds should be grown under the normal 20 hours of daily light until ready to harvest, which is often around 10-11 weeks. Deep water culture for autoflower cannabis is perhaps the best way to push the yields from an autoflower seed to the max!

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Best cannabis seeds suitable for the DWC technique

All strains should grow well in DWC. Arguably the heaviest yielding cannabis seeds bring the best out of DWC. That’s because DWC allows maximised yields when done well.

Recent USA cannabis seeds deliver a superb combination of genuine XXL yields with top quality smoke/vape experiences and sky high THC levels. They are all highly recommended for growing in DWC systems.

DWC recommendations and tips for maximum harvest

Becoming an expert DWC cannabis grower can take many years. The following tips may help you avoid some mistakes and may help you on the way to becoming a more proficient DWC cannabis grower!

Calibration and replacement of pH and EC meters in DWC systems

Many DWC growers have regretted not calibrating their pH and EC meters. It’s easy to buy pH calibration fluids to allow you to ensure your pH meter is reading correctly. Remember that one day it will start to fail. Many good growers have relied on a faulty meter and compromised plant health severely as a result with nutrient burn from the DWC feed.

The best growers check the calibration on all their pH and EC meters each day to ensure that they are reading correctly. The very top DWC cannabis growers keep replacement meters, in preparation for the inevitable day when their meter will fail.

Switching cannabis from DWC to soil

Some growers have started growing their cannabis plants in DWC and then put them in soil to finish growing. This can be done if you are careful. The plant needs to be removed carefully from the DWC system and the roots need to be delicately laid down into the soil (or coco). Slowly add soil without snapping the roots and water well when complete. Note that it will take several days for the cannabis plant to adapt to the new grow medium, be patient.

DWC cannabis grows and nutrient temperature management

This is another area of key interest to those growing cannabis with a DWC system. The higher the temperature, the faster root growth can occur until certain limits are reached. However, harmful bacteria, algae and slime can also grow more rapidly as temperatures exceed much above 24ºC (75ºF).

Your nutrient bath will also need more frequent changes. Many prefer temperatures a few degrees cooler than that, which make the bath less inviting for unwanted bacteria, algae and slime. However, with cooler DWC nutrient conditions, the experienced DWC cannabis grower will note a different root growth profile. However, for many DWC growers, temperatures as low as 18-20ºC (64-68ºF) are preferred and regarded as optimum. Many potential DWC weed growers ask ‘Do I need a water chiller with a cannabis DWC grow?’. The answer in almost all cases is yes.

Cooling is essential for indoor growers especially in warmer months. It is the extra hassle of needing a chiller, an air pump/air stone, pH/EC meters, calibration tools etc which deters many from undertaking a DWC grow. This is a shame, since many of those that have become good DWC growers would probably advise people to persevere with the process of learning.

Often, within a grow or two you will have seen the amazing growth at root level matched with THC rich buds at canopy level. If you manage your DWC cannabis system well, the yields may well surpass those from soil or coco fibre grows under the same light/growroom conditions in a faster time period.

Leaving water to stand for a day before use

One tip from the old school DWC cannabis growers is to leave tap water for a day or so to de-gas before use. This allows chlorine, for example, to leave the water.

Emptying the old nutrients easily in a DWC system

If you have a DWC system that’s difficult to drain, buy yourself a battery operated liquid pump. It’s long and reaches down to the bottom of your tank.

Using reverse osmosis water for DWC cannabis growing

Many expert DWC growers like to have full control over all nutrients entering their nutrient reservoir. That means using a special filtration system known as reverse osmosis to remove most/all of the minerals that are naturally present in our water supply.

It may seem like excessive levels of control, but many that are attracted to DWC enjoy applying maximum control wherever they can. Seeing a cannabis seed transform into a cannabis plant of maximum size is the most satisfying sight for the expert DWC grower.

Use LED grow lights when growing cannabis with DWC

If you are a serious grower intent on mastering perhaps the fastest way to grow heavy cannabis yields, then you may well want to use the best grow lights too. These days the best and most serious growers prefer to use LED grow lights. With an optimised light spectrum and reduced levels of heat stress they deliver superior quality and THC levels if you can justify the initial cost of purchase.

Noisy air pump tips for DWC cannabis growers

Instead of laying the air pump on the ground, consider hanging it on a rubber bungee cable. The noise and vibrations may be reduced. For those growing in noise-sensitive environments like apartments or bed rooms, air pump noise can be a concern.

Don’t pack the cannabis plants in too densely in a DWC system

Remember each well grown plant can be a metre+ tall and just as wide, don’t plant too many cannabis seeds in close proximity. Aim to grow a small number of monster plants. If you grow them well, you won’t need many!