Spyder7answered grow question 4 years ago There's no "rule" that you can't, but growing directly from a 5 gallon pot has drawbacks. I've experienced enough of them growing in a 3 gallon this grow to learn that I won't do it again, but will start in a solo cup then transplant in week 2/3 directly to the 3 (or in your case the 5).
The drawback of growing directly from seed (germinated in paper towel or not) in a 3 or 5 gallon pot is that the plant can't take up much water until it has developed its roots (by about week 2 or 3), but you still need to keep the soil moist since the microbes in the soil need water, so you're having to routinely water 3-5 gallons of soil that your plant isn't drinking yet, which is a pain. Its much harder to avoid the dual over/under water pitfalls when growing directly from a 3 or 5 gallon pot and its why a lot of people don't do it, even with autos.