Flushing Out the Truth in a Controlled Indoor Growing Environment

By Rich Hamilton
Published: July 24, 2020 | Last updated: April 23, 2021 01:28:15
Key Takeaways

What’s all the fuss with flushing? Water or nutes? What’s best? Well... let’s go back to basics first and look at why we need to do it.

Most fruit/yield producing plants have a vascular system that takes in nutrients, water starches, and sugar around the plants via the roots and feeds the entire plant, including the leaves, to fuel the photosynthesis process. This in turn helps the fruits develop, along with the overall growth of the plant. The vascular system can also store substances such as dissolved nutrients, water, unused sugar, and starch for later use. Plants do this for a few reasons. The first is they are producing more energy than they can use, so any spare energy is transferred into a form of sugar and/or starch and stored within the plant. The second reason is to store a small amount of energy in case of drought or a shortage of light. The third reason is the larger the reserve a plant can store, then the more reserves it has to make it through the winter/non-growth period. These sugars and starches are on-hand ready to be used almost immediately should the plant need them, and it is these energy-rich reserves we want to release through the flushing and ripening phase.


Flushing Removes Stored Nutrients in Plants

Excess reserves are mainly stored within the stem and root ball. With a plant growing in a natural environment, these deposits would consist of natural low-level chemical elements, ready to be released as the plant needs them.

Read also: Building up the Brix for Healthier, Nutrient-Dense Crops


In a controlled indoor growing environment, plants are given nutrient-rich feed which is more concentrated as you are trying to replicate the natural growing cycle, but in a shorter space of time. To do this, there is normally a chemical-rich nutrient feeding solution that fuels the rapid growth of the plants. While these nutrients are a vital part of producing your crops, they often leave unwanted chemical traces within the plants. These traces can manifest themselves in the plant as a chemical-like taste, smell, or color. To remove these unwanted effects, most hydroponic growers, whether they are hobbyists or commercial, will flush their plants. This flush is intended to clean the plant of the unwanted chemicals still being stored within.

Flush Plants with Chemicals or Water

With flushing you have two options: a chemical nutrient flush, along the lines of the feeds and supplements you have already been using, or simply use water. Of course, whatever you choose is a matter of personal preference, however, what I can say is using a chemical flush will certainly help speed things up. I must add at this point that if you do decide to just flush with water alone, remember it is important to hold the pH of the water during the process. If it is too high or too low, your plant can absorb extra aluminum and salt from the water, which will lead to a whole new set of problems.

Flushing: A Two-part Process

The first part of the flush process is where we halt all further intake of nutrient elements and remove the excess chemical traces of nutrients from the plant’s system. The second part of the flush, or the ripening, is where we want to drive out the active chemical elements stored as reserves in the plants’ vascular system and push them into your plants’ fruits. The focus and key to this process is on speed — the faster the plant is flushed of all active chemical elements then the faster it can move on to the ripening stage where the plants’ reserve stores are being used.

On entering the ripening phase, whether you were or were not previously using a chemical flush, you should now switch to just water as this allows the plant to utilize its reserves as quickly as possible after the chemical flush has done its job. By forcing the plant to use these reserves you are boosting your plants and the fruits will quickly grow again in size and weight. It will also bring out all those complex deep flavors that you want. Thinking of it as two separate stages can help you to keep your mind on what it is you are trying to do, which is to get the biggest, heaviest, tastiest fruit in the shortest amount of time.


Read also: Flushing for Soil and Hydroponic Gardens

In a natural environment, under natural conditions, water alone will and does perform the flush process over a much longer timeframe, which is more than effective as plants grown outside in the wild have less of a concentration of stored nutrients in them as their lifecycle is much longer.


Water alone is not enough for plants grown under indoor conditions as doing so uses constructed systems to get the most out of the plant in the shortest amount of time possible, and to the best of its potential. Under these conditions, a flushing agent is much more efficient. It will speed the flushing stage up more than water alone by at least a week. How is that you may ask?

Flushing Agents Attract More Chemical Molecules

While the whole process is very complicated, the principle is simple. Think of the water molecule as an “L” shape traveling around the vascular system, diluting the active elements by picking off the chemical molecules. The shape of the water molecule is effective, however, it is not the best or the most effective shape it could be, and this is where the flushing agent comes in as superior.

In contrast, imagine the molecule of the flushing agent shape is a “+” shape. If you look at it, it’s four “L’s” back-to-back, and therefore four times as effective as the “L” shaped water molecule alone. As the flushing agent moves around the plant’s vascular system, it will attract quadruple the amount of chemical molecules to it than the water molecule would, and so dilute and flush the active chemical elements out of the plant faster. This is great as it quickly pushes the plant into the next phase of the flush. As soon as the vascular system is not providing the plant with the nutrients it needs, it will start to release and use up the reserves it had stored previously, which will induce flowering and fruiting to its full potential, maturing your plants produce faster.

Two of the most common reasons people grow indoors is for speed of growth and a higher yield. That’s why using a chemical flush is as important as using nutrient feed. If you used neither and only watered your plants, of course they would grow and yield eventually, but would it be as high or quick? Of course not. It defeats the point of all the hard work and effort you have put in if, at the end of your grow, you don’t maximize your efforts by flushing your plants effectively. You could be missing out on some amazing results.


Share This Article

  • Facebook
  • LinkedIn
  • Twitter

Written by Rich Hamilton | Writer, Consultant, Author of The Growers Guide

Profile Picture of Rich Hamilton

Rich Hamilton has been in the hydroponics industry for more than 20 years, working originally as a general manager in a hydroponics retail outlet before becoming an account manager at Century Growsystems. He enjoys working on a daily basis with shop owners, manufacturers, distributors, and end users to develop premium products.

Related Articles

Go back to top
Maximum Yield Logo

You must be 19 years of age or older to enter this site.

Please confirm your date of birth:

This feature requires cookies to be enabled