We have a potted lime tree that is 10 years old. It flowered this year, much to our amazement up here in New England, and now it has little fruits. This might sound dumb, but how can I tell when the fruits are ripe? They start out green and stay green. Thank you!
Is that a Persian lime? Well, when they get maybe hen's egg sized and start to get almost a little soft. Well, at least not rock hard. I've seen limes ripen to yellow here in Fl.
Key limes grow to usually quarter sized in dia. and also turn yellow; then fall off.
I've had lime peel oil/leaf oil + sunlight make dark brown 'spots' on my hands before.
I would also say to squeeze it. When you are at the grocery store, squeeze some from there so you can kind of tell what a ripe one should feel like. It will be more of a feel thing rather than a look thing probably to tell when it is ripe.