Old grape vine
I moved in to a new house and inherited a grape vine with three woody trunks. Last summer the vine covered the whole side of my house and was great, but not very productive and I'd like to retrain it.
Is cutting back lower than those knobbled trunks risky? They kind of grow haphazardly, one trunk slightly slitting, and I had thought about taking it down to ground level and train one new single trunk - the vine clearly has very well established roots now.