Expect to wait about 13 years for the avocado fruit if you start with the pit in a glass of water. The good news is that you could be eating your own avocados in four years if you start with a healthy, nursery-grown plant. You'll need to wait several days for the flesh of avocados to soften after picking them when they reach a good size. Avocados don't ripen on trees, so you'll need to pick them when they're big enough.