Productive life span of HTs
I've noticed that several of my best producers and strongest plants, notably Valencia and Parole, start out gangbusters at 1 1/2 -2 years old, peak at around four years old, then start to level off and then decline in production and vigor. No change in fertilising schedule. By the time they're 8 years old, they seem to be pretty much spent. Is this the norm for modern HTS, or is it a question of varieties?