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The simplest plant growth hack; dechlorinate your water!

Why should you use a horticultural / hydroponic dechlorinator?

Chlorine is routinely added to tap water all around the world. It is an excellent biocide for destroying microbial contaminants which could cause ill health. At the level used in drinking water it is safe to humans, doesn’t taint the taste, is non-residual and doesn’t accumulate in the environment.

Whilst this is widely known and accepted, what many people don’t realise is that chlorine being ‘extremely safe’, does not also apply to plant life. As such, commercial greenhouse/hydroponic growers can cause problems for themselves if they add chlorine to their recycled water to prevent unwanted microbes reaching problematic concentrations. This includes stunted roots and scorched foliage.

However, what may surprise you is that even at the level of chlorine found in tap water, chlorine can actually harm plants. We are not just talking about sensitive herbaceous plants such as radish and lettuce, but hardy perennials like willow and hydrangea. In a 2008 study these shrubs were harmed at levels as low as 2.5mg/L – which is well within the level found in tap water (Cayanan et. al., 2008).

Compounding this issue further is the fact that chlorination levels in tap water are purposely increased in summer to combat the extra potential for microbes to grow in warm conditions. But this is the main season in which your plants need watering with tap water!

Even if you grow a plant that is hard as nails, and is completely immune to the effects of chlorine, we would still recommend using a dechlorinating product. Why? Because all plants exist in a close symbiotic relationship with microbes living next to their roots. These beneficial microbes perform many essential tasks that aid plant growth, including solubilising nutrients, protecting against disease, helping tolerate environmental stresses, and synthesising plant hormones. The chlorine added to the tap water is just as toxic to these beneficial microbes as it is to the human pathogens which the water authority are trying to eliminate. So, just as you want to help maintain a healthy gut flora in your body, you want to do everything you can to ensure your plants’ own microbial biome flourishes.

So how do you prevent chlorine damage to plants? Well, you have two options:

  1. Leave your irrigation water to sit overnight. This will allow the chlorine compounds to ‘gas off’ into the air. This saves you money on buying a dechlorinator, but obviously is an inconvenience. This option is also a non-starter for commercial growers due to the logistics involved and the need to keep irrigation systems running constantly. Plus, chlorination of tap water is now being supplemented with the addition of ‘chloramines’, which are much more persistent, and will take far longer to dissipate from tap water that has been left to sit.
  2. Add a small amount of dechlorinator to your water. This will instantly deactivate all of the active chlorine compounds in your water. This is by far the easiest method, and as you only need 0.5mL per 10 litres of water, the cost is negligible.

So, if you think you have your growing environment optimised, you’re using the best possible fertilizers, pests and diseases have been eliminated, then the next logical step for taking your growing to the next level is to include a simple dechlorination step every time you irrigate.

But don’t just reach for any old dechlorinator…

Industrial dechlorinators contain sodium, which is highly toxic to plants. So adding one of them would cause more problems than the chlorine in the water was doing. You need a dedicated dechlorinator designed for plants, and at Eutrema we are confident that our Horticultural Dechlorinator is the best product tailored specifically for plants. This is because it:

  • Lacks sodium
  • Is extremely high strength
  • Has a stable shelf-life with no discolouration over time.
  • After it has reacted with the free chlorine, it releases plant-available calcium. This is a major plus for people who are fertilising their plants with standard ‘garden centre’ fertilisers in soft water areas, as these fertilisers always lack calcium, and there will be no calcium being delivered through the hardness in the tap water. As such, Horticultural Dechlorinator is solving two problems for these growers.

For commercial growers we would particularly recommend Horticultural Dechlorinator to growers of fresh leafy vegetables, such as lettuce. These crops are routinely treated with chlorine, and this leads to the distinctive ‘swimming pool’ smell on many lettuce farms. This smell is due to the creation of chloramines when free chlorine reacts with the ammonia from the fertilisers. These chloramines are still potent and will reduce plant growth significantly, and as such a deactivation of the chlorine once the microbial issue has been addressed is advised.

Whilst many horticultural nurseries have not yet realised the power of dechlorinating their tap water, in other sectors its use is more widespread. Many indoor / vertical farmers use a hydroponic dechlorinator as they can easily measure the yield improvement resulting from water treatment,



Cayanan, D. F., Zheng, Y., Zhang, P., Graham, T., Dixon, M., Chong, C., & Llewellyn, J. (2008). Sensitivity of Five Container-grown Nursery Species to Chlorine in Overhead Irrigation Water, HortScience horts, 43(6), 1882-1887. Retrieved Nov 2, 2022, from

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