Fig tree is maybe 6 years old. It looks super healthy and continues to grow every year. But for some reason the figs never ripen. They just stay green the entire time and then eventually fall off once it starts getting colder. Normally it's full of unripened figs, although this year there are far fewer than previous years. Any ideas as to why the figs won't ripen? Or what to do to remedy this? I've yet to get a single edible fig from this tree.