What is the maximum depth of roots

how deep do roots grow?

one of these days id like to design a grow that provides ample root depth - like 3 ft, 5 ft or more.

I see these huge outdoors grows such as from the humbolt people and they use enormous puck shaped grow bags. the 1000 gallon ones get 2-3 feet deep. Is that really all the depth roots need?

vertical height in my grow is severely limited - 4 ft. This topic is more just a thought exercise for me (for now), but maybe you all know the answer?

Good question. I am not sure what they really need. I don;t know much about whether plant root prefer to extend horizontally or vertically. Base on what my 5 and 10 gallon root balls looked like after harvest, it seems they will go in either direction as long as there is loose soil and nutrients. I think if you are going to veg for a long time, like outdoors over summer time or even indoors for whatever reason, you definitely need more room for your roots or you end up with a dense root ball that struggles to take up water and nutrients, or dries out super quickly.

1 Like

Just thought I would throw this lil tid bit of information out there…
Plants roots will grow to how ever big the container is when its put into a container , but if you take the same plant and put it into the ground , when you dig it up the main root ball will only be about 20 inches in diameter and reach out roughly to 3 feet of wispy roots… even if it’s the size of a tree … I dont know why that is… but it is… :wink:



That’s interesting. I always assumed a plant’s roots would be approximately same width as the canopy. Similar to trees.

1 Like

Not sure how many plants are like this , but I know MJ is… but from the 2 years that I was in Humboldt county , we were growing massive trees in the ground and in big grow bags so I’ve seen this first hand… it’s weird that the roots will fill a 1000 gallon pot but in the ground they never really reach any farther then 3 feet down or 3 feet from side to side… :wink:



Very cool info! Thanks for the knowledge.

1 Like

now i have more questions. is it the greater air saturation that leads to roots filling a container but limiting growth of mj in the ground? would the root penetrate the full depth of a grow bag if i was 5 feet deep but on the surface of the ground, meaning the soil 5 feet deep would still have good air exposure

I think its because its alive… in other words… when it’s in a pot , it knows that it has limitations and wants to make sure that it has the best chance for survival and when it’s in the ground it probably don’t feel the need to search out its limitations because it can sense that it’s one with the planet and has no limits , so then it only grows out as far as it needs to to be happy and healthy…
That’s my thoughts on it … :wink:



i guess one way to find out would be to have a 10,000 gallon container converted to hydro and see how big it gets… but with a long enough veg there are no grow limits, right?

one could start with a 95 gallon garbage can.

1 Like

any dwc growers want to comment?

will roots grow to fill this?

or will they max out in size eventually?

1 Like

Seems to me root formation depends on a lot of variables. Time allowed to veg, density of soil, quality of soil / medium being used and on and on. Roots will look for the “water table” and nutrients and will grow to the extent needed to find them and sustain the plant. Might explain difference of pot vs ground planted simply due to availability of needs elements?

I am sure they would max out at some point. But in DWC roots die and roots grow. It’s not the same as a plant in the ground. I’m sure if you had a big enough space to veg that long you’d fill it. But it still wouldn’t truly answer the question because the roots can’t expand they can only grow straight down due to gravity. And once they get to a certain point where they feel crowded they’d stop. Look up hygrohybrid on YouTube. He I know did a big trashcan RDWC grow but it won’t let me share the video. And I can’t remember if he shows the roots.

Eventually I’ll be growing single photo plants in my 40 gallon totes. That may give us a chance to see how big the roots will get before running out of room up top or below.


Plant root growth comes from the genes. So it’s strain specific how a plant grows. Also based on what you do and don’t do to your plant. Every single factor that does effect the plant changes the grow.

I personally have grown outdoor plants, planted in the ground that have grown 25’+ tall, and have width of 20’+ or more in girth.

After harvesting and digging in the ground the roots were vastly deeper and wider than I dug. I’d urge that the roots are larger and more vast than the part of the plant that protrudes out of the ground, and gives us all that wonder fruit and oil we love.

But, when I put my plants in the ground after last frost. My girls going in the ground are 7-12 weeks old. I personally try to encourage root growth with the method of buring the plant in a way that the roots and a large part of the plant are buried upon planting.

I learned this method growing tomatoes. Promotes massive roots. Helps me since I do LST bending on my plants, and try and SCROG my outdoor plants.

Me too. Learn something new every day. Happy cake day @DoobieNoobie

1 Like