DWC/Hydro Growers Flush for a Few Days – When a hydro/DWC grower changes their reservoir to plain water, their plants literally have access to almost zero nutrients immediately. Because of that, a hydro grower should usually only flush their plant for a few days before harvest to prevent early yellowing.
All the nutrients were used up in the plant, including the ones in the sugar leaves, causing unsightly yellowing on the buds/sugar leaves that’s almost impossible to trim off.
What is the Point of Flushing Before Harvest? (Leaching Extra Nutrients Out of Buds)
I grew three plants. I had one plant I didn’t flush at all, one that was flushed for a couple of days, and one that got flushed for a little more than a week.
2.) Provide only plain pH’ed water to plant until harvest (from a few days to 2+ weeks)
- Beneficial root bacteria – Hydroponic growers should continue using products with beneficial root bacteria like Hydroguard right up until harvest. These products do not contain any nutrients but will protect your plants from root rot.
- Continue to manage the pH of your water as normal – PH Up and Down products don’t contain added nutrients. If the pH is too high or too low, it makes certain types of salts and aluminum more available to your plant roots. You don’t want your plant absorbing that stuff up right when you’re trying to flush the buds!
- Blackstrap molasses – This all-natural bud sweetener is safe to use up until harvest in coco or soil grows (1/2 tsp per gallon of water), but not in hydro.
- “Clearing” or “Salt Leaching” Solutions (below) – These supplements have been specifically designed to help remove extra nutrients during the flush.
Note: You still need to pH the water during the flush, because too high or too low pH can cause your plant to absorb extra aluminum and salt out of the water!
This example shows a normal bud where sugar leaves remained green at harvest, no yellow spots
Not pH’ing Your Water During Flush
Flushing before harvest can increase the quality of your buds, but it can also hurt your yields and even REDUCE the quality of your buds if you do it too early! Learn how to flush properly!
- Flushing your plants does not involve robbing them off nutrients. On the contrary, it allows your plants the chance to use the excess nutrients they have accumulated throughout the grow cycle. When you feed your crops full nutrient loads right up until the time of harvest, they retain an overabundance of compounds that affect the quality of the final product — including its taste, smell and overall smoothness.It’s also important to note that the main purpose behind flushing is not to encourage substantial new growth — although, flushing can cause your crop’s floral blooms to swell, since plants are not expelling all their energy on nutrient uptake.
- Any grower who has experienced nutrient burn knows the argument that plants cannot expel excess nutrients holds no weight. Ask any seasoned cultivator how to fix nutrient burn and they will tell you: You need to flush your plants and allow them time to use up the excess nutrients.The same logic applies to pre-harvest flushing. You’re giving your plants just enough time to use up surplus nutrients, salts and other compounds.
- The argument that soil can’t be effectively flushed is simply illogical and just plain wrong. Plants grown in soil can be flushed — it just takes a longer period of time than flushing plants grown in hydro or coco.
- It’s true that withholding nutrients places stress on plants and causes them to increase defense compounds. However, in certain plants, the primary defense compounds are actually the most desirable constituents, so flushing before harvest can significantly increase the value of the final product.
- At Advanced Nutrients, we employ the largest team of Ph.D. botanists, microbiologists, entomologists, hormone specialists and organic chemists in the industry. These scientists are dedicated solely to studying cultivation best practices and are constantly conducting laboratory research. The notion that plant flushing is “pseudoscience” is simply absurd.
At the same time, your plants utilize the stored nutrients they need during these last few days and hours prior to harvest. A high-quality flushing agent will provide your plants the support they need through this process, along with assisting them in purging the excess compounds that you don’t want in your final product.
Let’s address these anti-flushing arguments one by one.
Along with using the right flushing agent, you need to ensure you’re flushing at the right time in order to reap the maximum benefits of flushing. Use the following as guidelines for flushing prior to harvest:
Though some in the industry have argued otherwise, the importance of flushing your plants has been affirmed by the vast majority of serious growers. Most experienced cultivators have tried not flushing before harvest, which has caused them to experience first-hand the glaring difference in quality of the yield.You see, during the growing cycle, your plants store excess amounts of nutrients, salts and other compounds. If you don’t allow the plants a chance to dispose of these surplus compounds by flushing them before harvest, your final product will be much harsher and more bitter tasting. Failing to flush can also cause your product to suffer from other negative side effects, such as black ash and an unpleasant chemical taste and smell.
Despite the overwhelming majority of growers who understand the importance of flushing and have verified its benefits through their own practice, there are some who argue against it.
- If you’re growing in soil, begin flushing between one and two weeks before harvest.
- If you’re growing in coco, flush your plants for up to one week prior to harvest.
- If you’re growing in hydro, your plants only need to be flushed for one to two days.
Before we get into the reasons why flushing your plants is so important, we need to understand exactly what it is. Flushing involves watering your plants without any added nutrients for a period of time — anywhere from a day or two to a week or more, depending on your growing medium — prior to harvesting. The purpose of this is to allow the plants time to use up the nutrients that have already built up within them, thereby lessening the overall nutrient and contaminant load of the final product.
- Robbing plants of nutrients at any stage of the grow cycle is counterproductive and does not benefit growth in any way.
- Once nutrients are absorbed into the plant tissues, they are there permanently. The plant cannot expel them or use them up simply by denying it more nutrients.
- If flushing was in fact a beneficial practice, then plants grown in hydro would always taste better than plants grown in soil because soil cannot be effectively flushed.
- Withholding nutrients causes stress to the plants, which impedes growth rather than encouraging it.
- Flushing plants is “pseudoscience” that has not been supported or backed by any legitimate scientific studies.
We're exploring the truth about plant flushing: what it is, why it’s so important, and the best way to go about flushing for maximum benefit.