A potted lemon tree is fine.
If your tree has no lemons, you can purchase them from a grocery store.
When performing this ritual, pray to your Innermost to command the elementals of the lemon tree and the lemon to combine their forces, and to work on behalf of your benefit in accordance with the law.
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami