The roots of an avocado can take anywhere between 8–16 weeks to start and even longer to produce fruit. This all depends on which part of the world you're living given soil conditions, climate etc. Seedling avocados can take up to three months from seed to shoot. And seven years to fruit only problem is you need two trees for cross pollination or another tree close by in a neighboring yard to get them to fruit. Plus some trees require an ‘A’ and ‘B’ type to get the best fruiting crop out of them.