Motion-Activated Sprinklers. Keeping deer out of gardens can drive a gardener crazy! I successfully installed a system of 4 motion-activated sprinklers to keep deer out of a garden this summer. They work by squirting the deer but also scaring them with the sound. The sprinklers are motion-activated, so the deer do not learn to ignore them. The only limit, however, is you can’t use them during freezing conditions.
https://www.youtube.com/watch?v=NSDmxIjqdZg