Its very possible to go from seed to harvest (30 day veg, 60 day flower) with a 7 gallon pot, It might not be ideal depending on strain but I've actually seen it done in 5 gallon pots. He yielded a pound from one 600w and one 5 gallon pot with one plant. A 7 gallon pot is plenty for 1 plant thats goin 90 days from seed to harvest. Thats just from my experience and what I've seen.