Olive trees originally come from the Mediterranean region. In this area, summer is hot and dry and winter is typically wet and mild. Because of this, olive trees tend to do best in climates that are similar to these conditions.
Commercial olive trees are typically cultivated by grafting. This process involves cutting a branch from a tree that is producing good fruit and tying it to a tree that does not produce good fruit. Over time, the branch will grow and cause the tree to produce good fruit.
Without this process, an olive tree seed will usually revert to its wild form and produce small, hard fruits. Because of this, growing an olive tree from seed will usually not produce a good olive harvest. The tree itself is still considered to be great for ornamental purposes.
Plant the seed after the danger of frost has passed. In general, olive trees can survive in temperatures of 12 degrees Fahrenheit for short periods of time, but they will not be able to sustain a prolonged freeze. Even after the tree takes root, remember to cover it up if the weather gets too cold.
To plant an olive tree from seed, start by cleaning all of the fruit off a fresh olive seed. After picking off what you can by hand, rub the seed with wet sand or salt to remove all traces of the olive fruit. Ideally, use fresh olives. Pickled and processed olives typically have damaged seeds that are not good for germinating. Repeat this process for about five seeds.
Next, soak the seeds in a jar or glass of water for 20 days. Make sure to change the water in the jar or glass daily. If you want to save some time, rub the seeds on sandpaper until their surface is broken. Skipping this step will decrease the number of seeds that actually germinate.
After the seeds coats have cracked, fill a pot that is at least eight inches wide with a mixture of seasoned manure, sand and potting soil measured in equal amounts. Make a one inch hole in the middle of the pot and place one seed in the center of the hole. Cover the seed with more of the soil mixture, then add water until the soil mixture is damp. Repeat this for each seed.
Finally, put a clear plastic bag over the top of the pot, and fasten it with a rubber band. Take the bag off every three days and add water so that the soil remains damp. Place the pots in a window or other location where they will get filtered sunlight. Make sure that the temperature stays above 55 degrees Fahrenheit. The seeds should germinate in about three months.
As soon as the seedling sprouts, remove the plastic bag. Remember to plant in the spring. If possible keep the saplings covered during cold winters for at least the first three years.