The Rhizosphere is the narrow region of soil that is directly influenced by your cannabis roots and the symbiotically associated microorganisms within the medium. That which is not part of the rhizosphere is known as bulk soil. Understanding the distinction between the two could keep you from wasting thousands of dollars on bulk soil, which simply offers no added value.
Last summer while visiting the folks at Greenlight Gardens in Grants Pass, Oregon, we learned a lot about roots, rhizosphere and container size. Owners Tony and Sarah Sandoval were more than halfway into their outdoor season–row after row of 10-foot-tall and even wider plants precisely where they harvested a 21.5 pound plant in 2015. Yes, 21.5 pounds of dried, cured bud from one plant, and that’s not counting popcorn and larfy under buds. Just as I began to comment about the enormity of the 500-gallon pots that housed these giants, Sarah was quick to point out how much smaller they were from last season and, furthermore, how they plan to harvest more bud from these smaller containers.
In 2015, the couple utilized 700-gallon fabric pots. After harvest and upon closer examination of their plants’ roots, they learned that over 200 gallons of soil toward the top of the containers was unpenetrated by even upward lurching lateral roots. “We noticed, as above so below,” commented Sarah, meaning that the root structure of their plants grew almost precisely diametrically opposed to the plant’s canopy. As the roots dive so does the plant grow tall and as the roots branch out so too does the canopy show similar fractal-like, lateral growth. That said, the Sandovals not only used less soil this year, but they also changed the shape of their containers to more precisely match the shape of the rhizosphere, rendering as little bulk soil as possible. Their new approach was two-tiered, with a smaller diameter (100 or so gallon container wall) which sat upon a wider 300-ish gallon fabric pot. So in light of their discoveries, the Grants Pass team is saving tens of thousands of dollars while harvesting more bud from less soil, by accommodating the natural growth pattern of the roots.
This notion was confirmed at Craig the Outlaw’s guerrilla grow in Tehachapi, CA where he did side-by-side comparisons over a 10-year run on the same public land. He started with 500 gallon pots and later discovered that he could pull much more from a harvest by planting several plants in recycled hot tubs which “are free on craigslist all the time.” As rotting hot tub trash began to pile up over the years, he decided to clean the entire lot and plant directly into 100-ish gallon holes, that he dug by hand, to reveal his best harvest yet, using 20% of the soil he used for his first harvest on the property.
At Nate-O Headquarters outside Bozeman, MT, the team switched to smaller 7-gallon Airpot containers indoors to maximize lateral roots and minimize bulk soil. This industrial grow does uniform six-footers with two feet of canopy atop and naked to the ground, where each plant lives in 7’s. After decreasing pot size every couple of harvests, the boys from Montana realized that there was zero compromise to bud and/or plant size or quality as their containers got smaller. After years of side-by-side, research and development, they came to the realization that they could grow the same sized colas and overall weight from 7’s as they could in the 20-gallon pots they started with in 2003.
Over the years, research into their rhizosphere revealed precisely the same findings as the Sandovals in Grants Pass, Oregon. Even in 7-gallon pots, Nate-O and company still found almost a gallon of bulk soil up around the surface of their pots–that is until they switched to Airpots 7-gallon product. The idea, that they have confirmed with their own grow is that they could get even bigger plants by switching to the solution which allowed for the most lateral root growth. After sampling several different containers that boasted about increased lateral roots and minimizing bulk soil, the group settled upon the Airpots containers based on their own findings. Now they are growing the biggest colas and the heaviest plants they have in 14-years at the same location and with minimal soil and infrastructure investment. According to Nate, “Dropping flower prices and increased competition on the black market have forced us to find creative ways to cut costs without sacrificing quality and this is just one of a bag full of tricks we’ve learned along the way…it’s the natural progression of any good business.” Nate swears you’re wasting money if your flowering indoors in anything bigger than 7’s.
I have several experienced grower friends who would disagree with Nate, however the point is that roots talk. Listen to your plants and understand that as above, so below. Experiment with different containers–sizes, shapes and composition and see what worms, mycorrhizae, compost tea and food-grade probiotics and amino acids can bring to the organic equation. Create a symbiotic symphony in your beds, always remembering less is more, to maximize rhizosphere size and functionality, then watch your canopy flourish above. And keep from wasting money on needless bulk soil and valuable space indoors with bulky pots if you’re only growing 4 to 6 footers. After harvest, dig your roots up and examine them. Are they healthy? How much of your container is bulk soil? How did changing one variable or introducing different allies affect your roots? Take photos–compare and contrast harvests and be sure to share your findings with friends, including us–visit growmag.com and connect to show us what you’ve found.