Flushing plants is one of the final steps in the growing cycle, and means harvest is just around the corner.
This is a pivotal point, and improper flushing can lead to an unenjoyable final product with poor smell and taste, and a harsh smoke.
Worse yet, some growers omit flushing altogether, leaving behind all kinds of nutrients that they then consume with their flower.
We're going to cover best practices and teach you how to flush your plants properly, and recommend some of the best flushing agents currently on the market. We want to start by explaining what flushing is, exactly, and why it's so important.
What does flushing plants mean?
Flushing plants involves using plain water or a flushing agent to literally “flush” built-up nutrients. You’ll stop feeding any nutrients at all, and your feeding chart (if you are using a complete nutrient package) will account for this.
Often times, nutrient packages, such as the Fox Farm Soil Nutrient Package, including their own flushing agent. But, many growers just use plain water (pH’d to the ideal range, of course) to achieve the same effect.
Later on towards the end, we’ll cover whether one is better than the other and describe exactly how you should go about flushing your plants.
Before we do that, we want to cover the importance of flushing plants.
Why do you need to flush plants?
In the final few weeks of flower, you’ll need to start flushing plants to push out the last bit of bud development and allow the residual nutrients built up in your plant to be used.
At the end of your grow cycle, you can likely visually see the salt deposits on the sides of your pot and even in your soil.
The image above is an extreme case of this, and an indication that the grower is either overfeeding or using super-concentrated salt-based nutrients.
Do buds still grow during flushing?
Yes, buds still grow during flushing. In fact, you’ll see some of the best bud development in the flushing period, as your plant uses up the rest of the nutrients within it.
It thinks it's starving, and senses the end of its life is near.
The buds will fatten up the most in the final few weeks of flower, and you’ll also notice more trichome production.
Furthermore, your plants will produce more terpenes and flavonoids during this period than the rest of the growing cycle. This is because your plant is making a last-ditch effort to get pollinated.
Some evidence also suggests that because your plant is no longer using energy to uptake nutrients, it is able to spend ALL its energy pushing bud flower development and terpene production.
What happens if you don’t flush?
If you don’t flush your plants, you’ll end up harvesting flower with residual salts within it. That will contribute to a harsher smoke.
And, you won’t get the true taste and aroma of your flower, even if you dry and cure your buds properly.
How To Flush Plants
There are slightly different protocols for flushing plants depending on your growing method. Traditionally grown plants will need to be flushed slightly longer than those grown hydroponically.
No matter how you grow, you should start flushing plants when you believe they are ready for harvest. To determine they are ready, use a magnifying glass to get a closer look at your trichomes.
When more than 50% of them have turned from a translucent white to a milky white, you are ready to start the flush.
They’ll still have some time to turn that amber color that many growers look for when determining if its the right time to harvest.
How to flush soil & coco plants
If you grow in soil, you’ll have the longest flush period. Most experts recommend at least a week, and as long as 2 weeks of plain water or using a flushing agent.
If you're growing in coco, however, you'll probably be fine with a week or less. Coco doesn't hold onto nutrients to the same degree that soil mixes do.
Every grow will have different requirements, depending on the nutrients you feed, the exact media, and environmental conditions.
You can watch your foliage to determine the progress of your flush. Your leaves will start to yellow, which is normal.
But if you notice yellowing of your buds, you may have overdone it, and your plant is starting to die. At that point, you’ll need to chop them down and get to harvesting.
How to flush hydroponic plants
If you grow in a hydroponic system, your flush will be super quick. It will likely only take 3 days or less to flush out residual nutrients from your plants.
Additional tips for flushing your plants
We want to reiterate how important it is to flush your plants at the right time. The harvest window itself is pretty narrow, and thus the flushing window is as well.
If you flush too early, you'll end up depleting nutrients during a critical time, and your plant won't have the energy it needs to finish flowering.
On the other hand, waiting too long to harvest can lead to a decrease in potency as well. The reason is, you're flushing when your plants should already be chopped down.
It's also important that you pH your water when flushing your plants. Otherwise you'll develop weird irregularities such as yellowing from nutrient deficiencies.
What are the best flushing agents?
There’s a ton of debate over whether water does as good a job at flushing plants as flushing agents do.
For most hobby growers, plain water is fine. If you are in the market for a complete nutrient package, though, it’s not a bad idea to just grab a flushing agent while you’re at it.
They are specially formulated to remove residuals from your plant, and have specialized chelates that actually grab onto any extra salts lurking in your plants.
If you are a commercial grower cultivating plants for sale, you absolutely should be using a flushing agent. Your reputation is on the line, and you can’t afford to risk leaving salts behind that affect the quality of your smoke.
Here are some of the top flushing products on the market.
South Cascade Organics SLF-100
SLF-100 is a commercially proven enzymatic formula with over 18 years of proven success. It is a 100% organic and OMRI listed formula specifically designed to break out salts. Used as a cleanser for hydroponic systems and soilless media, SLF-100 goes to work immediately to keep your system running smooth and free of toxic buildup.
SLF-100 is effective in all phases of the growing cycle and is compatible with all nutrients, fertilizers, and rooting compounds. SLF-100 is also compatible with H2O2. Thanks to a proprietary blend of naturally occurring enzymes, SLF-100 is PH neutral in concentrated form and has no added sugars or NPK.
Mix: 1 tsp per gallon of water. Apply thoroughly once a week.
Hydro: 1/2 tsp per gallon of water. Apply after feeding/changeout.
Flush: Up to 2x recommended rate for immediate break out. Apply thoroughly once a day for three days.
Athena Blended Cleanse
Athena Cleanse is made from the ideal (and safe) root zone optimizing agent--Hypochlorous acid. This safe and mild acid is derived from salt and a proprietary electrochemical treatment process. The result is a unique, plant-safe chemical with powerful oxidative properties to keep your root zone clean and free of unwanted organisms and buildup. These special properties improve both mineral and oxygen availability in the growing media.
- Non-toxic - Safe to use on plants in and stage of growth
- Neutral pH - Won't affect solution stability
- Increases Oxidation-Reduction Potential (ORP)
- Breaks down scale - Keeps irrigation systems in pristine condition
- Reduces biofilm - Keep lines clear of dangerous organic material
- Very low TDS - Doesn't throw off mineral balance
- Promotes robust root growth
- Effective as a final flush to clean growing media
- Keeps irrigation system cleaner and running efficiently longer
- Reduces mineral buildup in media and lines
- Increases oxygen and nutrient availability in growing media
Cultured Solutions UC Roots
Cultured Solutions™ was formulated specifically for high performance water culture applications such as our Under Current™, so as to maximize production and yields while minimizing the waste and excess often associated with hydroponics cultivation. Our well balanced, extremely concentrated mineral nutrient enables plants to thrive at relatively low concentrations, while maintaining unparalleled performance and quality.
Cultured Solutions™ potent formulation provides US growers with a premium plant nutrient without incurring the large carbon footprint associated with importing foreign nutrient lines. With high quality mineral inputs, pure Sierra Nevada water and exceptional chemistry, Current Culture H2O™ has created a Premium Plant Nutrient. It's our innovation, horticultural expertise and commitment to excellence that's enabled us to formulate and blend the best nutrient line in the world...right here in California!
UC ROOTS is a multipurpose root zone optimizer that uses proprietary chemistry to aid in mineral descaling and the removal of potentially harmful biofilms in nutrient reservoirs. By reducing the potential habitat for plant pathogens, UC ROOTS has been shown to aid in root development.
- Periodic: Add 5-7mL of UC ROOTS per gallon of water and continue to irrigate as normal. Continue this process for 12-24 hrs. then drain away solution and mix new nutrient.
- Final: Add 5-7mL of UC ROOTS per gallon of water and continue to irrigate as normal. Continue this process for the last 3-5 days of fruiting/blooming cycle.
Botanicare Clearex - Salt Leaching Solution
Botanicare Clearex is one of the best ways to eliminate built up salt deposits in your soil or soilless grow.
It’s a scientifically formulated isotronic drench solution.
This means it can actually bind to the salts residing within your plant or soil, and leach them away.
Some additional benefits of Clearex include:
- Preventing wilting
- Gentle leaching without harming fine root hairs
- Triggers the final reproductive stage for that explosive bud and terpene development we mentioned earlier
- Increased flavor and yields as well
General Hydroponics FloraKleen
General Hydroponics FloraKleen is another reputable product from a well-trusted brand. It works not only in traditional media and soils, but in hydroponic systems as well.
It can be used throughout pivotal points in the growing cycle, such as between veg and flower, but most importantly, right before harvest.
FloraKleen does exactly what a flushing agent should. It improves flavor by dissolving minerals and salt deposits, while contributing to a smoother smoke.
Some additional benefits include:
- Dissolves accumulated fertilizer salts
- Reduces plant stress from excess or imbalanced nutrient ratios
- Safe for all systems and media
- Ultra concentrated and low priced, making it a cost effective solution for your grow.
Fox Farm Bushdoctor Sledgehammer
Fox Farm Bushdoctor Sledgehammer is a unique flushing agent, in that it not only helps rinse excess fertilizer from the media and your plant.
It also helps encourage water movement through the media and release surface tension. This allows for optimal absorption of moisture and nutrition through the root system.
So, all those built up nutrient salts you are flushing will actually still get used by the plant!
Its derived from Saponin, a Yucca extract. This means its organic and natural, suitable for any type of grow. For best results, it should be used in conjunction with the entire Fox Farm Feeding Schedule.
Final Thoughts On Flushing Plants
Now that you know why and how to flush your plants, you can ensure your flower comes out clean, tasty, enjoyable, and most importantly, developed to its full potential.
After flushing, its the moment you've been waiting for - harvest. While you flush, you can check out our complete guide on harvesting, drying, and curing.
It will help you prepare for the big day, and the days that follow, to help set you up for a perfect harvest that results in flower you can brag about.
You should also grab all your harvest supplies while you're here. Whether you plan on trimming by hand or using a trimming machine, we have what you need at the best prices online, and provide world-class service that will have you itching to come back again.