God has created Reiki to be equally effective for all the living beings. When plants and animals are given Reiki, they enjoy it, develop better and express the joy in their own way. Since we do not understand their language and feelings, we do not comprehend their reaction instantly but with little deeper thought one can at least guess it. Here is one of my personal experiences.
On a hot day of Summer 2010, while standing under a tree and waiting for something, I found a sick or injured yellow wasp lying on ground that was caught by ants. The wasp was struggling to get away but was unable to do so. Rather than watching the game silently or killing the wasp, I decided to help her and started giving her Reiki. Just after few minutes, the wasp gained enough strength, got rid of ants and flew away. After a while, a yellow wasp came flying and sat on lower part of my trouser (below the knee) rather than attacking me, which was a pleasant surprise. Where she sat was safe for me, which made me to think that it was the same wasp who came back to thank me for help.
The method I used to give Reiki to wasp is quite simple and I teach it in Reiki second degree. This method can be used to give Reiki to any human being, plant or animal. If you are a Reiki healer, consider helping the needy animals especially your pets. That will be a positive gesture and would get you positive return.
Similarly, plants can also be given Reiki. A sick or underdeveloped plant would be pleased to receive Reiki. You may like to give it a try and see the results for yourself.