Growers paradise or stoner nightmare?

By Tony, Dutch Passion Seed Company, Amsterdam

Deep Water Culture, or ‘DWC’, is regarded by many as the fastest way to grow cannabis.  Other less charitable home growers will claim it is simply too technically demanding and has ruined countless cannabis grows due to the complexity of the technique.  So what is DWC and is it worth the effort?

DWC is a hydroponic (soil-free) system of plant cultivation which suspends the plant roots in a solution of nutrient-rich, highly oxygenated water. Normally cannabis roots would simply rot if left in water, but an air-stone (or similar) at the bottom of the nutrient bucket ensures that the roots are bathed in an oxygen-rich nutrient solution which keeps them healthy and allows rapid growth.  The air-stone needs to run for 24 hours a day.

Over the years many different types of DWC have evolved.  Although they use the same basic principle the technique can be modified according to the available equipment.

DWC may offer rapid growth of cannabis plants, but it is not recommended for the inexperienced.  If you prepare the nutrient concentration wrongly, or forget to check your plants then its easy for DWC to go wrong, and to do so very quickly.  DWC requires the grower to know and understand the different feeding requirements at different stages of plant growth.  And DWC requires precision in the way you prepare the nutrient pH (level of acidity) and EC (nutrient concentration). Even a small mistake, or a faulty pH meter/EC meter can cost you an entire grow with DWC.  Like many things in life, the risk can be worth taking when you know what you are doing.

Traditional DWC systems tend to use plastic buckets with the plant contained in a net pot suspended from top.   The net pots often contain a cube of glass-wool or clay pebbles.  Seeds are easy to germinate in rock-wool cubes.  The roots grow downwards and are suspended in the nutrient solution in the bucket, often 20 litres or more in size. An air stone at the bottom of the bucket oxygenates the nutrient solution. With both oxygen and nutrients the roots will grow rapidly and the plant will be able to reach a large size and produce plenty of cannabis.  As experienced cannabis growers already know, a healthy abundant root system is essential if you want to grow monster cannabis plants.

Recirculating deep water culture, also known as RDWC, is another variant of traditional DWC.  RDWC uses a reservoir to provide water for multiple buckets.  If the buckets are connected together you can run multiple buckets/plants without the hassle of checking/adjusting individual buckets for pH and EC.  Aeration of the nutrient solution can take place with a large air-stone in the central reservoir.  The use of spray bars in some RDWC systems also allows oxygenation of nutrients.  The constant recirculation ensures a good mix of nutrients and makes sure that pH and nutrient concentration is the same in each bucket.  This is great when a single variety is being grown, however it means compromises have to be made if you are running different varieties with different nutrient requirements.  One of the requirements of any DWC system is an experienced grower who knows how to keep the plants in the nutrient ‘sweet spot’ throughout the grow. 

The best DWC growers do not under-feed plants in early development, this limits growth.  Over-feeding plants is even more damaging and can permanently stunt the growth of a small plant.  In order to be a good DWC grower you will probably have learned the basics of cannabis growing from soil or coco-fibre growing.

One variant of DWC called Bubbleponics involves dripping feed in thru the top of the plant container in addition to the normal bucket of nutrient solution with an air stone at the base.  Bubbleponics takes feed solution from the nutrient bucket and pumps it up through a circular dripper ring at the base of the plant.  This helps early plant growth, especially in the period while the baby roots are reaching down into the nutrient solution.  The dripper ring runs for 24 hours a day and devotee’s of RDWC will claim it allows a faster start and results in bigger final yields. 

The DWC nutrient solution is often changed every 5-7 days to ensure a fresh batch of nutrients.  In-between nutrient changes growers will often top-up the volumes check and adjust their pH and EC every day. The pH is often kept around 5.8, if pH drifts it becomes impossible for the roots to absorb certain minerals even if they are present in the nutrient solution.  This is often called ‘nutrient lockout’, and adding more nutrients won’t solve the problem, the only option is to change the nutrients for a fresh bath with correct pH and EC.  Many DWC growers have lost an entire crop because they relied on an uncalibrated pH/EC meter. Eventually every pH/EC meter fails and gives erroneous readings.  Thats why the best DWC growers have back-up meters and calibrate regularly. 

Mature female plants will often drink several litres of nutrient solution each day, the lost volume has to be replaced or eventually the nutrient solution is consumed and the plant will die.  One of the criticisms of DWC is the need to regularly check the plants and replenish feed solutions.  If you need to spend periods of time away from your grow room then DWC may not be the best system for you.  However if you enjoy checking your plants regularly and have the skills, then DWC could be the fastest way to grow.

DWC growers need to keep their system clean, regularly removing any slime/sludge build up and wiping down surfaces to remove salt and mineral splashes.   Algae will form readily in a nutrient solution especially if light can reach down into the nutrients and provide the energy required for algae growth.  

DWC is a high-maintenance grow technique, it needs skill, time, precision and effort.  Some people love the challenge and rewards on offer from DWC. Others have tried it and felt it was an expensive error which over-complicated their passion for home growing and removed the fun.  If you do decide to attempt DWC then research it thoroughly and remember that few DWC growers master the technique on their first grow.  

This article first appeared in Issue 123 of Weed World Magazine