I think the "roots as big as tree" quote is a bit off these days. I grew my second potted plant in an amended Coco based organic potting mix in a 2.5 gallon pot and she filled a 2x4 tent pretty well on its own.
If that old saying was true none of my plants would have been more than 8-9" tall as they were all in 20-25cm pots.
This. Truth be told, people don't make as much use of their 5 gallon or more sized pots.
Consider roots in a solo cup; we've all checked roots too early (breaks apart), or too late (rootbound).
With roots,
its mass we should care about and not size. Lets take the following example.
Consider a fully rootbound 2g pot vs a half way full 7g pot.
I can yield 2.5-3.5oz from a 2g pot, translates into 1.25-1.75oz per gallon. We'll say average 1.5oz per gallon.
I can pull 6-8oz from a 7g pot, translates into 0.85-1.14oz per gallon. We'll say average of 1oz per gallon.
Now, assume a 4x4 tent. 4x4 tent can fill either 4 7g pots, or 16 2g pots. Lets compare the yields of both scenarios using the numbers from above.
4 7g pots = 4 plants in 7g pots, 1oz per gallon. 7 x 4 = 28g x 1 oz = 28 ounces.
16 2g pots = 16 plants in 2g pots, 1.5oz per gallon. 16 x 2 = 32 gallons. 32g x 1.5 oz = 48 ounces.
Or 32g x 1.25 oz = 40 ounces.
Or 32g x 1 oz = 32 ounces, still an extra QP compared to 7g pots.
You can yield almost double by using smaller pots. The reason is because many people underestimate just how much soil is truly being used by the plants and their roots.
I've had root masses in 2g pots that were like literal bricks, there was that many roots in the pot. They had to be watered twice a day, and the watering took forever. There were so many roots in the pot that the water could barely even flow through!
Compare that to a 7g pot that isn't near as root bound. In fact, attempting to transplant this 7g pot will likely result in a broken root ball because there aren't enough roots in that 7g pot to hold together the 7g of soil in the pots.
Which plant will drink more water and consume more nutrients? The 100% root bound 2g pot or the half way root bound 7g pot?
7g pot is more likely to experience issues related to overwatering and root rot. The 7g pot will only need to be watered 2-3 times a week, and fed one a week.
The 2g pot though? Needed to be watered 2-3 times
a day, and had to be top dressed/amended twice a week.
If the 2g pot eats and drinks more than the 7g pot, it stands to reason it will yield more too.
I've since begun phasing out anything larger than 2g pots. I don't have to veg as long as I did with 7g pots and yield more because I can fit more plants and have a tighter canopy as a result. Easier to move them around too. I can grab 4 of the 2g pots using both of my hands. I can only grab 1 of the 7g pots using both of my hands.
Do the side by side and see for yourself. The 7g pots will require 4-6 weeks longer veg than the 2 pots will. And even if the 7g pots receive the extra 4-6 weeks of veg, they'll still likely not yield as much as the 16 2g pots.
Furthermore, in the span of a year, the extra veg time for the 7g pots results in less harvests. Resulting in even less weed for us!
That extra 1 month of veg time, multiplied by 3 harvests in a year, results in a loss of 3 months due to extra veg time.
That 3 months you lose from vegging, could have been another harvest. Not only do the smaller pots yield more, but they'll provide you with an extra harvest in a year compared to the 7g pots.
Electric bills are cheaper too, because that's 3 months the lights are 12/12 instead of 18/6 or 24/0.
Regards.