Every single day we have people coming into The Hydro Store wanting to purchase huge 30 litre pots to grow in. The majority of these purchases are with the buyers in search of bigger yields, as they are of the understanding that if plants are put in a bigger pot ( and changing nothing else ) they will get bigger yields.
A lot of hydroponic /grow shops will go along with this, even recommending bigger pots as a way of getting customers to need buy more growing medium, but unfortunately it is an untruth.
How do we know? A few years back we put this to the test, taking three rows of plants and putting one row in 30 litre pots and the other two in 15 litre pots. The plants were in the vegetative stage for an average /standard amount of time with 4-6 plants per 600w light and the plants in the LARGER pots YIELDED LESS.
After conducting our test, we examined the roots in the two different size pots and found the roots in the 30 litre pots were barely filling the pot whilst the root mass in the 15 litre pots were huge and really healthy. This allowed the plant in the 15 litre pot to feed more and produce more of a bountiful harvest.
The simple fact is that if you want to grow in a larger pot to achieve bigger yields you also need to grow / vegetate your plant for a lot longer to allow the plant to establish a full root zone within that pot.
So, on the understanding that you are growing 4 to 5 plants under one 600W light, we always recommend establishing your cuttings /seedlings in 1 or 2 litre pots then re-potting them into a maximum of a 15 -20 litre pots. This is on the understanding that you are growing 4-5 plants under 1 600w light. Bigger simply isn’t always better!