The olive tree can be propagated by stem or hardwood cuttings, rooted truncheons, grafting and seedlings. Collect cuttings, truncheons and grafts on hot days, 85 to 95 degrees F (30 to 36 C), to minimize shock to parent trees and propagated material.
Planting from a seedling will give you the advantage of a deep root tap, which will make the tree less susceptible to drought and disease. On the other side, it makes it more difficult for water to get down in to the deep seated roots.
If you choose to plant from seedling, this is what you will need to do.
Step 1: Find and Plant a Seed from a Fresh Olive
You must have a pit from an olive picked directly from a tree. Olive seeds pickled in brine are dead, and will not germinate. Plant it in a shallow pit and water it regularly.
Step 2: Care and Maintenance of the Olive Seedling
It will take at least two years to germinate, due to the fruit-bearing pattern of olive trees.
If you have an olive tree that you want to clone, you can do this with grafting. It's a more complicated process, but it will give you a tree that is identical to its parent. Grafting can take more than 2 years to produce any olives.
Step 1: Choose Seedlings to Receive Grafts
Pick a strong, healthy seedling with limbs at least 1 inch in diameter. Make a shallow cut in the limb with a double-bladed grafting knife.
Step 2: Attach the Graft
Peel back the bark carefully and insert a bud wood patch from a younger seedling. The patch should be 1/2 inch across, with a visible bud sprout. Seal the bud graft to the limb with cellulose tape. Watch and water in droplets carefully to prevent over watering.
Many people find it much easier to purchase a tree that has already started. Planting a seedling or grafting is definitely not for the beginner gardener. Olive trees by nature are more difficult to get rooted and get a healthy tree. The trees that have already been started and only need to be transplanted will generally produce olives more quickly and without the headache involved in grafting.