Avocados are subtropical trees native to southern Mexico, and they grow best in semihumid climates with moderate temperatures (60° to 80°F). Even the most coldhardy varieties ('Mexicola' or 'Topa Topa') freeze at about 25°F, Dr. Bender says.
You can, however, grow avocados in containers and move them inside during cold weather, but there are no dwarf varieties available, so the trees tend to get too big within about three years.
Organic Gardening contributing editor Willi Evans Galloway wanted to be really sure that avocados would not survive in Zone 8. So she called up the local Jacksonville, Texas extension horticulture agent, Joseph Daniel. "I'm afraid that we're a little too far north for avocados," says Daniel. "We can have fun germinating the seed and growing the plant for a while, but that's about as far as we can take it." So it seems the only avocados you'll be picking will be from the supermarket. But if you still want to grow your own indoor baby avocado tree, the California Avocado Commission has helpful instructions online at www.avocado.org.