Everything about flushing your cannabis plants

Everything about flushing your cannabis plants

We examine everything about flushing your plants. Find the best cannabis nutrient flushing tips and what mistakes to avoid in the process.

Experienced home cultivators and novices alike can benefit from understanding what it means to “flush” cannabis plants and why it’s important in producing a successful crop. Thankfully, this underrated and easy process can determine the difference between a harsh, difficult to burn disaster and a successful, tasty yield.

Although flushing isn’t complex, there are several key factors you must consider in order to perform the task correctly. Below, we take a look at everything about flushing your plants; from the best time to do it, to just how much the process influences a crop’s results.


Classical methods for growing cannabis in soil call for cultivators to administer three essential nutrients, nitrogen, phosphorus and potassium, or NPK, to bolster the vigorous growth and yield of their cannabis plants. While these elements can increase a plant’s ability to thrive under tough conditions and flower magnificently looking, potent buds, an uneven balance of NPK can affect the final product in less than desirable ways. This is where flushing comes into play.

Simply put, flushing is the process of watering your plants without any added nutrients in order to expel chemical buildup from within the plant tissue. This course essentially forces plants to absorb and process excess nutrients without storing any unnecessary minerals.

While pure water is additive-free, it still contains reduced levels of essential nutrients like calcium, that positively influence growth and don’t necessitate human interference. Something to keep in mind when flushing, is to optimize the pH of your water. Watering cannabis with a pH, that is too high or low may affect the salt levels in your crop and set you back just as far as if you didn’t flush at all.


The results of an unflushed plant are most noticeable during smoking. Some telltale signs include particularly harsh and “chemical” tasting smoke, as well as black burning ash, in contrast to the greyish color it should be. Additionally, the flower may be extra difficult to burn, resulting in unneeded frustration on behalf of the consumer.

Flushing is somewhat of a catch-all for ensuring your plants haven’t received too much feeding. This irrigation process allows for a better tasting crop simply by applying water like you would any other houseplant - there’s no reason not to do it!

While unflushed bud isn’t the end of the world, it is a disheartening reminder, that an entire crop can be greatly affected by the smallest of errors. Seasoned cultivators will remind you, that you can’t cut corners and expect to produce a fabulous product - even the most menial tasks maintain importance in the growing process and have remained over the years for that very reason.

When flushing, you want to make sure you administer enough water to hold the nutrients and flush them out. This may require watering the plant once, waiting a few minutes, then adding more water until it flows clear out of the growing vessel.


Finding the right moment to start flushing your plants is contingent on your growing method and how close the crop is to harvest. When growing in soil, cultivators should consider flushing about two weeks before harvesting, toward the end of the growth cycle, when trichomes begin to form a cloudy white color.

In hydroponic operations, flushing is even more straightforward, as the nutrient bath the plants’ roots are suspended in is simply exchanged with pH balanced water. Unlike soil growing, however, hydroponics only require a few days of flushing to get the job done.

Flushing your plants too early and often will culminate in the expulsion of too many minerals, stunting the crop’s ability to flourish and produce flowers. While you don’t want excess minerals, you also don’t want to deprive your plant of the nutrients it needs to grow robustly. Another fault of flushing too early is the increased proliferation of yellowing or discolored leaves that give the plant an unsightly look.


Flushing is not a perfect process. Inevitably, the water will not be able to fully leach all of the NPK and other media from the plant’s root system and tissue; however, the amounts will be significantly decreased.

Additional flushing methods can be purchased in stores, that ensure greater efficacy in removing nutrients, however, these processes carry the potential of destroying a plant’s root system, among other nasty side effects.

Growing is a variable process, one that is altered by many factors, including, but not limited to flushing. In cases where extreme, toxic levels of nutrients are administered to a plant, the negative manifestations of not flushing can be severe. In cases of consistently grown hydroponic crops, that received appropriate concentrations of these elements throughout their lifespan, failure to flush will be less noticeable.

Whether you are growing hydroponically or in soil, flushing is an omnipresent technique in mainstream cannabis cultivation, that airs on the side of caution. Though it’s possible, that flushing won’t significantly improve the taste of your finished buds, refusing to flush carries the potential for a lackluster crop, that could have been easily avoided.


The only way to really find out yourself if flushing makes a difference is to conduct a controlled experiment of your own. A good technique is to grow two clones of the same cannabis strain simultaneously under the exact same conditions. This includes giving them equal sunlight and feeding them the same nutrients.

When it comes time to flush, only apply it to one plant. Once the flowers have been harvested, trimmed and cured, perform a smoke test and record the results. You’ll be able to tell right away if the bud tastes A-okay or is better off being converted into cannabutter.