Marijuana roots are the foundational hydraulics and stabilizing system absolutely necessary for your plants to grow. You want marijuana roots as healthy, dense, and efficient as possible.
This article tells you how to boost root development, but many growers neglect root development, in part because it’s hard if not impossible to see roots while the plant is growing unless you use pure hydroponics systems such as deep water culture buckets or aeroponics.
With those systems, you can can pull roots up to examine them, although this should be done only a few seconds at a time and as infrequently as possible.
Healthy roots are nearly pure white, and they’re shiny, densely branched, there are no black or brown spots, no mush.
If cannabis roots are in a container too small for them, roots are squeezed too tight by lack of space. They start circling in on themselves. Root function is compromised.
One way to avoid this is to grow in air pots designed to do “air pruning” that turns off root expansion without forcing the roots to circle themselves and otherwise get too compacted.
Air pots and cloth pots are also better than solid pots because they allow increased oxygenation of the root zone.
Roots in a solid root zone media such as soil, rockwool, soilless mix or coco coir need ample pore space for root growth and movement, oxygenation, and moisture.
High-quality Grodan rockwool and quality coco coir have very favorable water-retention, drainage, pH, and oxygenation characteristics for marijuana roots’ health and function.
But many types of soil and other root zone media can be too dense for marijuana roots, and should be aerated with super coarse perlite. Please note: use only super coarse perlite, and be sure to wash it first, as perlite is coated in dust that harms your root zone and is a severe respiratory irritant.
You may have to experiment with how much perlite you add to a root media. You want the media to be porous and a little fluffy, but you also want it to retain moisture.
If you water a root zone and most of the water immediately runs out the bottom of the container, the media is too porous.
If you water a root zone and none or less than 10-15% of the water immediately runs out of the container, the media is too dense and should be aerated with coarse perlite.
Get in the habit of knowing how much your containers weigh when fully watered, moderately dry, and so dry that plants are at risk of wilting.
Note that too many marijuana growers overwater their roots, basically drowning them and reducing plant health and growth.
Your marijuana roots are strengthened, functionally-enhanced, and protected when you install beneficial bacteria and fungi in the root zone.
However, this is not recommended if you have a recirculating reservoir system, deep water culture, aeroponics or similar form of hydroponic system because beneficial microbes tend to colonize and foul hydroponic systems.
I’ve tested all the root zone beneficial microbes products and by far the best one is Root, made by RX Green.
Note that adding a half teaspoon of unsulfured blackstrap molasses per gallon to your nutrients water every couple of weeks is the best way to send carbohydrates into the root zone. Carbohydrates feed beneficial microbes.
This type of molasses is less expensive and far healthier for your root zone than so-called carbo boosters sold in hydroponics stores.
Marijuana roots do their best in temperatures from 68-73°F. If your grow room runs hot, having a chiller or otherwise cooling your nutrients water to 68-70°F is one way to diminish plant heat stress.
Of course, you ALWAYS want to use reverse osmosis water unless you have access to tested, totally clean well water or rain water. Municipal water contains chlorine, chloramine and other garbage that harms marijuana roots.
How do you know you have root problems? If you’re growing in pure hydroponics systems, pull the plants up and look at the roots. If they’re shiny, fat, and white, they’re healthy. If they’re brown and mushy, they’re diseased.
But you can’t pull up your roots to examine them when you’re growing in soil, soilless mix, rockwool, coco coir. In that case you watch for when your plants aren’t using water as fast as usual, growth is slow, nutrients problems are showing up on leaves, or roots are growing out of the bottom of the container.
If you have huge plants in small containers and plants start experiencing problems and you’ve checked all other likely causes, the problem could be that roots are rootbound and you need to transplant to a larger pot.
Or your plants could have root problems from overwatering, overfertilizing, underflushing, bad pH, or defective hydroponics nutrients and other defective feed programs.
Flushing every two weeks starting at the beginning of bloom phase, using either pure reverse osmosis water by itself or reverse osmosis water and Root, is a great strategy. I’ve yet to see any benefit to the expensive liquid flushing formulas sold in hydroponics stores.
You definitely want to get an Apera pH meter (see here) that measures root zone pH. It isn’t easy to adjust root zone pH, especially if you’re growing marijuana in soil, but bad root zone pH interferes with marijuana plants’ nutrients absorption and harms roots.
Another thing to look out for are marijuana pests that live in the root zone. These will almost always be root aphids or fungus gnats.
Root aphids are tough to kill, and often arrive in your grow room in the soil or soilless mix you buy.
Root aphids are a special nightmare because they’re in the root zone and you can’t easily see them until aphid populations reach infestation levels, when winged aphids climb up stems and fly to uninfested plants.
Root aphids and other pests mentioned here cause considerable damage to your crop by being in buds and on leaves, and especially by leaving feces in your buds.
Worse yet, root aphids can live in a variety of root zone media, including coconut coir, rockwool, and soil, and there are few effective biological controls for root aphids. One biological control that works are specific types of entomopathogenic fungi (Beauveria bassiana, Isaria fumosorosea).”
Entomopathogenic fungus works by attaching to the aphid’s cuticle, penetrating the cuticle by enzymes and force, multiplying and spreading in the aphid’s blood via blastospores, and sporulating to continue the infection process.
This method is typically very effective, but aphids combat the fungus by molting off the previous cuticle. Entomopathogenic fungi need time to germinate and penetrate before the cuticle is shed. Therefore, to ensure optimal efficacy, it’s important for growers to incorporate an insect growth regulator such as azadirachtin to slow or stop the aphid’s molting process.
Fungus gnats show up when you have an overly wet or organic root zone with smelly components on top. Fungus gnat larvae eat your roots. One of the easiest ways to prevent or get rid of fungus gnats is to put a thick layer of coarse perlite on top of your root zone.
I always do root post-mortems to see how big my root mass was, how much of the pot it filled, whether there was girdling or other rootbound symptoms, if the roots were healthy and white rather than brown or mushy.
Whenever I’ve had cannabis plants that underperformed or showed unusual stress problems or nutrients issues, the post-mortem has almost always revealed to me that roots weren’t as robust, large, and healthy as they should have been.
One reason root mass might not be big enough, or roots unhealthy in other ways, is that you’re not feeding the proper light wavelengths to your marijuana plants.
As we’ve said before, most grow light brands don’t have spectrums engineered by photobiologists who tested how marijuana responds to grow light spectral output. Their lights fail to deliver enough or any of the spectrum that fuels root growth.
Ask the grow light manufacturer how their spectrum affects root growth, although you can’t trust what most grow light manufacturers say, so you need to ask for technical proof, not just product hype.
Know that most grow lights, especially the open-array quantum board LED grow lights that claim to be full spectrum, often under-deliver red and far red wavelengths known to best stimulate root growth from seedling and clone all the way to finish.
Also know that delivering the correct amount of photosynthetic photon flux density (PPFD) to your plants from start to finish is essential for root development.
If you deliver the wrong light spectrum or insufficient PPFD to your plants from seedling or clone and throughout grow phase, root development is stunted. This means your marijuana plants may never deliver optimized growth rate, morphological development, yield, and potency.
Roots don’t like to be exposed to light, otherwise I’d be growing in glass containers so I would watch my roots like I used to watch ants in an ant farm.
You work hard to understand, monitor, feed and maximize your marijuana roots—but it’s well worth it–because marijuana roots are the root of all other marijuana plant functions.