This trendy fruit actually can’t ripen on the tree, making it a boon for both avocado farmers and you. Though they reach peak ripeness for only a brief time, you can tell by brushing the calyx—the bit that looks like a tiny stem. If the calyx comes off easily, the fruit is nice and ripe (though if there’s brown underneath, it’s probably overripe). If the calyx doesn’t come off, it’s not ready yet. You can also check out the color, which should be a deep green, assuming you’re eating a Hass. If you want to squeeze it, you can, since a ripe avocado will have a little give to it, but Ahern doesn’t recommend this because it’ll cause bruising when the fruit does ripen.