Is there a power tool that I can use to trim evergreens with?

Yes, there are electric hedge trimmers. They come in different sizes. The larger units are more powerful, but do not buy a model that is too heavy for you to handle.

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.