Thanks Carolynk, that's a good one.
Here are some videos I thought were helpful:
This one is all diagrams and that makes it easy to see what you're getting at. (Reality is always more tangly). It describes and shows the different systems of grape pruning really well.
https://www.youtube.com/watch?v=kf_M_RVWpC0
Then the question is, which system will be best for me?
The four armed kniffen, and umbrella kniffen are recommended for cool climate, in Maine.
He mentions concord, and also labrusca.
https://www.youtube.com/watch?v=nkJHaZSS5eQ
https://www.youtube.com/watch?v=0-XQ_ukRMFA
"Cane pruning" is the same as umbrella or "two armed" kniffen, in these videos from Oregon State.
https://www.youtube.com/watch?v=pCs03Mc2HKM
https://www.youtube.com/watch?v=mfd2V5DFDo0
And last not least, the cordon style pruning.
https://www.youtube.com/watch?v=um9p1eiGiwI
Cane pruning or kniffen looks easiest to do outdoors - I mean for making one or two cuts just to drag away the whole fruiting vine from the previous year... it is less pruning.
Where the cordon style, you have more of a defined shape that gets heavier each year while small stuff is pruned off. That might work better for the greenhouse. Less of a frost risk in the greenhouse too I suppose (although it is not heated).
I'm thinking that the risk of cordon outdoors in the north, is of losing a whole 'arm' in a bad season?
