Question: What do you mean when you refer to “pinching” plants?
Answer: That’s a horticulturist’s way of describing a very light job of pruning. Use coleus or chrysanthemums as examples, Both tend to grow tall and leggy if they’re not pruned in some way. The very best way is to prune them frequently and lightly, removing only the growing tip, perhaps 1/4-inch long. That will make the plants branch out, keeping them more compact. Since you can easily do that pruning with your thumbnail and index finger, it’s called “pinching.”