I’ve heard that some growers like to flush their systems during the final week before harvest. Is this something you recommend doing? If so, why, and how do I know when to start this process?

By Kyle Kushman | Last updated: December 14, 2021

mature cannabis plants

Flushing your plants before harvesting them, regardless of what you’re feeding them, is always a good idea. Healthy, rapidly growing plants will store excess nutrients over time. Much like humans store fat, plants store excess nutrients within their leaves that they can use if nutrient levels run low.

I recommend a gradual reduction of nutrients, much the same way we gradually increase nutrients as plants mature. Three weeks out from harvest, I cut the levels of all N-P-K products in half and discontinue all micronutrient inputs. Reducing nutrient applications before completely discontinuing all inputs helps plants transition to the ripening stage.

Two weeks from harvest, feed your plants plain water and an enzymatic formula. For plants grown in soil or soilless media, there’s no need for any pH adjusting during ripening. One week before harvest, only feed your plants plain water. All growers, regardless of the methodology or grow media being used, should use this flushing method.

Knowing when to begin this process can be as simple as looking at the calendar. You should be recording all factors concerning your crop cycle, and you can use the recommended flowering time your strain is known for. However, growth rates, overall health and other factors can reduce or increase the ideal harvest date by as much as 10%. But you’re in luck, there is a way to judge when that perfect harvest time has arrived.

Using a 30X, lighted magnifying glass, look over a few areas on several plants. Inspect the flowers to get a good view of the trichomes. Under magnification, trichomes look like little mushrooms. Early, immature trichomes are clear as glass and the heads are small. As they mature, these heads will swell to 2-4 times the thickness of the stalk. As the trichomes get closer to maturity, the stalks turn opaque. Within a week, trichome heads will turn milky or opaque as well. Once they begin to turn dark amber, you are nearing peak ripeness. When 5-10% of all the trichomes have turned amber, you have reached peak ripeness.

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Plant Nutrition Plant Types Harvest Cannabis

Written by Kyle Kushman | Cannabis Cultivator

Profile Picture of Kyle Kushman

Kyle Kushman is an internationally renowned marijuana cultivator whose collaborations have earned 13 Medical Cannabis Cups awards, including three US Cannabis Cups for Best Flowers. As the creator of Vegamatrix, the only line of vegan and organic nutrients designed for growing cannabis, Kyle continues to make advances for people who want to cultivate the purest, cleanest medicine possible.

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