I planted 2 cascades I trimmed one back to 1 bine and it stopped growing at about 3 1/2 feet. The plant is still very dark green which to me means it is very healthy, I dug the rhizome up being careful not to disturb the roots to much and found the roots to be growing very long over 20 inches and they are very white which also means to me they are very healthy. This plant is planted directly into the ground. My other cascade is in a 2 gallon pot and it has three bines i pinched about 4 shoots off of this plant and is now growing 3 more new shoots so i pinched two of them off now it has 3 bines, 2 bines are about 5 feet and the newer shoot is about 3 feet, it is green but could use some more N.
the Mt Hood is potted and is on par with the cascade in every attribute. the Nugget is also potted, it has one bine I pinched 3 shoots it is about 4 feet and pretty green the plants were planted on 16th of March. I fertilize with manure cow, bat and fish emulsion.
I keeps it organic.
Soooo I think if you trim it to 1 bine you will be freeing up alot of energy for the plant to concentrate on growing its rootmass. My neighbor who is a horticulturist and his wife is currently in school for horticulture say the same thing. He planted a Zeus on the 19th of April that is now almost 7 feet tall (1 bine) so i think he knows what he is doing and ill take his advise anyday.