I always assumed it was a keep em trimmed and honor system kinda thing. Haven't tried it yet though, and I'm not great at fine print rules and details kinda stuff. I miss being able to trust the honor systemSo..in growing in a solo cup, the only way I can see to keep sneeker roots from popping out is maybe a layer of landscape fabric before you put in your medium....but still the possibilty of a root growing through is there, especially with multiple feedings......