Cannabis

Home Grow 12: 3 Reasons to Flush Cannabis Pre-Harvest

Home Grow chronicles Dianna’s personal journey as a medical cannabis patient who registered and was approved by the Canadian government to grow cannabis in her home. Dianna’s experience is one grower’s point of view. Her ideas are neither the best nor the only proven methods for growing medicinal grade cannabis.


Indoor cultivator/Boveda blogger Dianna Donnelly believes in flushing her cannabis plants before harvest. Learn why some growers are pro-flushers and others are not.

According Jorge Cervantes, famous outdoor cannabis grower, the harvest stage of cultivation begins weeks before the actual cut. Surprised? Turns out harvest isn’t so cut and dry.

According Jorge Cervantes, famous outdoor cannabis grower, the harvest stage of cultivation begins weeks before the actual cut. Surprised? Turns out harvest isn’t so cut and dry.

BUT FIRST, A CAUTIONARY TALE ABOUT SKIPPING PRE-HARVEST PREP

Once upon a time, a guy I knew bragged about cutting a grove of flowering cannabis plants that he and some friends happened upon. (Obviously it was someone else’s grow.) 

So those cannabis bandits waited ’til midnight to cut down the plants. (So not cool, and totally against cannabis growers etiquette!) Next, the group dried a few colas on low in the oven, and smoked their selfish faces off. 

The group “greened out” immediately and suffered splitting headaches, too. (FYI: Being “greened out” describes experiencing too much THC at one time. Feels like being very drunk, followed by a wicked hangover.)

So if cannabis is used to ease nausea and vomiting from chemotherapy or other therapeutic treatments, why did these plants have the opposite effect on these botanical thieves?

The green thieves skipped the necessary pre-harvest steps that make flower a more pleasurable (and safer) smoke. Those plants were likely full of fertilizer residue. INSTANT KARMA!

DON’T BE THAT GUY, FLUSH BEFORE CUTTING DOWN CANNABIS

Flushing is when growers stop feeding plants anything but water prior to harvest. Flushing removes residual fertilizer from the roots, leaves and flower of the cannabis plant.

Two weeks before harvest, I moved my girls from a grow closet into a new grow tent. As expected, they responded well to this new tent, which is like a 360° mirror. Bud growth increased, along with the rapid pick up of trichomes. It was time to start pre-harvest prep.

Cannabis growing in a tent.

3 REASONS WHY I FLUSHED MY CANNABIS PLANTS BEFORE HARVEST

  1. Ingesting any part of the plant with fertilizer residue present can be dangerous, especially when smoked. 
    During the bloom stage, my plants’ cells or vessels (xylem) contain residual chemicals and nutrients from the bloom fertilizer.
  2. Plants are top-heavy. 
    In my mind, the soil also contained fertilizer residue. But ridding these chemicals isn’t the only reason to flush a cannabis plant’s soil.  Watering so much at once pushes the soil down, which stabilizes the roots and the plant. (Growers also use long bamboo stakes to stabilize plants during the blooming phase.) 
  3. Forces plants to “clean their plates.”
    Plants will use up all those remaining or saved nutrients in her cells and xylem.

HOW TO FLUSH CANNABIS PLANTS AND THEIR SOIL

Beware of ever feeding cannabis plants with time-release fertilizer pellets because it’s impossible to remove that fertilizer/food from the soil before you harvest your cannabis.

After my plants were in the tent for about a week, I stopped feeding them nutrients and Botanicare Pure Blend® Pro Bloom and put them on a water-only diet.

  1. From above, water each plant with 4 liters of water.
  2. With a turkey baster (LOL), remove the excess water that runs out of the drain holes and into the tray underneath to prevent the plant from reabsorbing any nutrient run-off. 
  3. Three days later, water 1 liter from below into the tray, so the roots can absorb the water.
  4. For the next 10 days, water 1 liter from below every other day.

SOME CULTIVATORS SKIP FLUSHING, HERES WHY I DIDNT SKIP THIS CRUCIAL PRE-HARVEST STEP

I’m home growing my own medicinal cannabis primarily for vaping and smoking. I’ll also reserve a portion to eat and convert into edible oil, which will be decarboxylated in the oven.

Even if you convert the flower into an edible, the nutrient residue remains (and is possibly toxic). When heated, fertilizer and pesticide residues can change into very detrimental compounds like hydrogen cyanide—very bad news. 

Because I use cannabis as medicine, I want to avoid ingesting fertilizer/pesticide residues into my lungs or digestive system. Only the purest product for me, especially now that I control cultivation as a home grower.

Organic fertilizers and pesticides are always best for my garden and a necessity for me since my Boston Terrier Molly shares the space with all of us.  This is not to say that “organic” is always safe. But for me, “organic” usually means something from my kitchen.

I hope flushing reduces the residue in my cannabis plants and their soil by the time I cut them down.

4 TELL-TALE SIGNS THAT FLOWER YOU’RE SMOKING WASN’T FLUSHED

If flower hasn’t been throughly flushed of residues before you smoke it, that cannabis can:

  • Have trouble staying lit
  • Make your lips and tongue tingle
  • Burn the throat
  • Produce dark or black ash (Conversely, the ash from clean dry carbon is light grey or even white. Which flower would you rather smoke?) 
Produce dark or black ash (Conversely, the ash from clean dry carbon is light grey or even white. Which flower would you rather smoke?)

2 REASONS SOME GROWERS SKIP FLUSHING BEFORE HARVESTING CANNABIS

Growers who don’t flush their cannabis argue:

  1. Plants metabolize all of the chemicals, so only a slight trace of chemical residue is left behind.
  2. Plants that are well-fed right up until harvest produce greater yields.

To me, clean cannabis is quality cannabis, so I will always flush.

Plus, I’m kinda picky.  I loathe the smell of sulphur, a common component in many fertilizers. I can detect residual sulphur even after bud is cured. Maybe that’s why I’m such a militant flusher!

How will I know when my flower is ready harvest? Stay tuned!


Dianna Donnelly

Dianna Donnelly is a cannabis educator, blogger, and freelance writer living in Kingston, Ontario. She counsels new patients on the safe and effective use of medicinal cannabis and believes that with enough time, cannabis, and coconut oil she can heal the world.

Dianna Donnelly’s posts are being provided for informational purposes only; they do not constitute an endorsement or an approval by Boveda or any of the products, services or opinions of Dianna Donnelly. Boveda bears no responsibility for the accuracy, legality or content of this post or links to the posts. Contact Dianna Donnelly for answers to questions regarding her content.

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