Flushing Cannabis — How And When To Flush Marijuana Plants - International Highlife

Flushing Cannabis — How And When To Flush Marijuana Plants 

Flushing is an optional step in cannabis cultivation, but many growers swear by it. According to “flushing fans,” this simple technique can take your cannabis to the next level. While flushing doesn’t seem to increase the potency of weed, some believe it makes a big difference in a strain’s flavor profile. Cannabis connoisseurs even claim “flushed weed” has a distinctive and highly-desirable aroma. 

Luckily for new cultivators, it’s easy to incorporate flushing into your routine. As long as you’re careful not to flush your plants too early, you can safely experiment with this technique at home. 

What Does “Flushing Cannabis” Mean? 

In cannabis cultivation, “flushing” means removing supplemental nutrients a few days or weeks before harvest. Instead of feeding your plants nutrient mixes, you’ll only use pure & pH-corrected water during a “flush.” For those growing in hydroponics units, you’ll need to replace your reservoir’s nutrient-enriched water with clean water to properly flush your plants. 

You can use flushing in any grow set-up and with any cannabis strain. However, in all cases, you should only flush your cannabis plants in the late flowering stage. It’s also crucial to continuously monitor pH levels to ensure your strains remain strong and healthy. 

Why Do People Flush Their Cannabis Plants?

There are still many debates over the merits of flushing marijuana. However, most people who favor flushing argue this technique improves the overall quality of their buds. By “flushing out” excess nutrients, buds may have more pleasing aromatics and flavors. Put another way, flushing may remove the “chemically” scent associated with supplemental nutrients. 

Many cannabis cultivators swear that flushed weed has a smoother feel versus non-flushed buds. People may use flushing to reduce the odds of a coughing fit while smoking marijuana. 

Although many cultivators agree that flushing enhances their weed smoking experience, there’s little scientific research supporting these claims. Also, flushing isn’t an essential part of the cannabis growth process. If you forget to flush your flowers, they will still be harvestable (provided you maintain a suitable grow environment). 

There are, however, a few preliminary studies that show flushing has no significant impact on the total THC concentration in harvested cannabis plants. This finding is important from a cost perspective. Cultivators can save money by putting their nutrients away pre-harvest. Since adding more nutrients doesn’t appear to make buds bigger or stronger than flushed cannabis, this strategy can reduce a cultivator’s total expenditure. 

Because cultivators have different opinions on flushing, you’ll need to test it on a few strains to see how it works for you. Some notice an improvement in their flushed buds, but others may not notice anything spectacular. After a few rounds of flushing different cannabis cultivars, you should have a good idea of whether flushing makes a difference for you. 

How Do You Flush Cannabis Plants? 

Flushing is arguably the simplest cannabis “cultivation hack.” All you have to do is stop using nutrients and stick to your standard watering schedule. Just be sure the pH in your water is always between 6 – 7 for soil or 5.5 – 6.1 for hydroponics.

The main issue new cultivators face when flushing is choosing when to start. Starting a flush too soon can trigger nutrient deficiencies that could reduce yields or stunt your plant’s growth. 

Generally, the later you wait to flush your plants, the better off you’ll be. Most weed cultivators recommend waiting until your strain is in an “early harvest” stage before you start flushing your plants. This means your weed should already have at least ~ 40% of trichomes that are somewhat cloudy. While most cultivators wouldn’t cut buds at this immature stage, it’s still possible to harvest them. By waiting till this late growth phase, cannabis cultivators will reduce the odds of hindering their plant’s growth with a final flush. 

Please read this “Cannabis Harvest Guide” for more details on inspecting late-stage buds. 

Cultivators also have to consider their growth medium and strain variety when choosing when to flush their plants. The fewer natural nutrients are in your soil, the less time you should flush your plants. For example, if you’re using a coco coir formula or a hydroponics device, please only flush your plants for a few days before harvest. There aren’t enough natural nutrients in these grow mediums to support cannabis for too long. 

By contrast, people using a standard potting soil can usually flush a photoperiod cannabis strain for about two weeks before harvest. The nutrients in loamy soil mixes usually provide cannabis with enough “food” to finish out the flowering stage. 

Please also factor in the average growth rate for your weed strain before deciding when to flush. Be sure to look up the average flowering schedule for your strain to prepare ahead of time. Also, remember that autoflowering strains tend to grow faster than photoperiod plants. If you need more info on how to cultivate autoflowering seeds, be sure to read this International High Life guide.

Can Flushing Harm Cannabis Plants?

All of the latest evidence on flushing suggests this practice is safe when performed correctly. Most significantly, cultivators need to start flushing shortly before harvest. As mentioned above, it’s best to begin flushing when flowers are already in the early harvest phase (i.e., almost half of the trichomes are milky white). Cannabis growers must also pay careful attention to their water’s pH levels and resist the urge to overwater. 

It can be tempting to add more water to your flowering schedule to “flush out” all of the nutrients in your soil. However, a true “flush” doesn’t require extra water. Only add moisture to your soil when it’s dry to the touch. 

While flushing your cannabis, please screen for potential warning signs like droopy leaves and stunted growth. Yellow fan leaves may indicate a nutrient or pH imbalance, but they aren’t always a cause for concern in late flowering. As your plant sends more energy to bud sites, the vibrant green on fan leaves will naturally fade. You may also notice a few fan leaves falling off your plant as it approaches late harvest. To learn more about diagnosing yellow fan leaves, read this previous International High Life guide

Have Fun With Flushing Your Flowers!

Not everyone agrees that flushing cannabis changes its flavor profile, but few people claim it’s a harmful technique. As long as you start flushing shortly before harvest with pH-corrected water, it’s safe to start using this strategy with your favorite strains. 

Please remember that the positives associated with flushing are highly subjective. Therefore, you may want to grow two batches of the same strain to test the value of flushing. Keep all of the growing conditions the same for two pots of this one strain, but only add flushing to one container. Once your buds are ready to use, you could compare the flavor, aroma, and feel of these strains to form your opinion on flushing. 


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