Season for Planting Hass Avocado. Hass avocados have a dark purple to almost black pebbly skin with excellent flavored fruit. Avocados (Persea spp.) are evergreen trees that grow delicious green fruit that surrounds a large pit or seed. Avocados grow in the warmest regions of the United States. You can propagate trees from seed, but to do so results in trees that vary in quality and quantity of fruit. For these reasons, budding and grafting are common methods of propagation.