Flower

Depends on temperature... the resulting temp x RH dictates how fast the plant drinks, ceteris paribus. This impacts how much you may need to dilute what you feed and. it should match rate of growth for that stage of life cycle, too. Check out some VPD charts... it's good info, but is not 100% fleshed out. so you'll see different suggestions for different life cycle stages depending on where you look. Even if you don't control environemnt, it's just a good concept to understand. if your temps are near ceiling of safe range, a little more RH can be beneficial. So many relativistic factors it's hard to give a simple black/white answer. 65% is as high as you'd ever want to go as far as microbial growth prevention.