There is no fool proof method in deterring deer, but here are the most recommended suggestions:
- Fencing: 10-12 feet high is usually listed, but may need to be as high as 14 feet. This can be expensive and impractical in some situations
- scare tactics: motion activated sprinklers are the usual choice, or a guard dog
- repellants: those that contain dried blood or use a predator urine seem to be reasonably effective, but may need to be reapplied after rain. Check your local garden center for products and apply as directed.
- alternative plantings: there are some plants that are less attractive to deer and are less likely to suffer damage (a really hungry deer will eat almost anything)
MSU has information on deer resistant plants at: http://www.ipm.msu.edu/uploads/files/deer_resistant_plants.pdf
There is also information on deer control at: http://www.ladybug.uconn.edu/FactSheets/deer-damage---control.php