Anyone who has seen "The Illusionist" will be familiar with a variant of Robert Houdin's classic "Orange Tree" illusion. In the original trick, Houdin brought an orange tree onstage, and commanded it to bloom. The audience watched on in amazement as nine oranges grew from the tree. They were then cut up and passed around the audience, verifying that they were real oranges. In the film, the illusionist makes the tree itself grow, which isn't possible without actual magical powers, but the original trick can be performed easily with the correct apparatus.
Set up the blooming orange tree so the operation lever is facing away from the audience, at the back of the tree. Insert oranges into the compartments located across the tree. The trees generally available today were designed by H. Marshall, based on Robert Houdin's original tree. The compartments are dark green in colour, located amongst the fake foliage, beneath the nine orange blossoms.
Introduce the trick in whatever way you see fit. Remember, you will normally find trees that just "bloom" oranges, but some types will also grow in size slightly. However, this is nothing like the seed-to-fruit-bearing-tree transformation in "The Illusionist."
Remove the nine orange blossoms and toss them to the ground. These have dart-like construction, and can generally be made to stick into the ground or a board when thrown. You can incorporate this action into your accompanying dialogue. For example, you could mention that this orange tree is especially resilient, or that it instantly replenishes itself when its blossoms are removed.
Pull the locking lever to set the device in motion. The oranges are obscured by flaps, which are peeled back when the lever has been pulled. The oranges will appear to slowly bloom from the tree, and the flaps that were previously covering them will slide back into position. The trick is now virtually complete; the only thing waiting is your dramatic reveal that they are real oranges.
Cut up an orange to show the insides, and then pass them around your audience. The audience will be sceptical at first, but after they've held the oranges themselves and confirmed that they are real, they will be genuinely impressed. Remember, the trick will lose its magic if you explain the mechanism to anybody. If you're interested in preserving your mystique, don't spill the details unless someone absolutely needs to know.