At least half-dozen taste or odor-based deer repellents are currently being marketed to homeowners. Unfortunately, none provide absolute protection from deer damage, and most are quite limited in their effectiveness in neighborhoods where deer populations are high.
In many instances, combinations of repellents are more effective than when used individually.
For example, taste-based repellents such as Miller's Hot Sauce® can be applied to browse-susceptible plants in a landscape bed according to label directions. Additional protection is then provided by hanging perforated 35mm film canisters (not as easy to come by as in the past) containing cotton balls saturated with odor-based repellents such as Hinder® or Deer-Away®/Big Game Repellent® from three foot-tall stakes driven six to ten feet apart throughout the bed. The film canister enclosures keep the repellent from weathering too quickly.
(Note that the mention of the products above are not an endorsement of their effectiveness.)
Regardless of technique or type of repellent(s) used, they must be introduced to the garden before deer begin to feed on susceptible plants. And, because they lose their effectiveness quickly when exposed to a variety of weather conditions, it’s necessary to reapply them a minimum of every two to four weeks, more frequently during wet weather, according to label directions. Their application can also be limited, or not possible during extended periods of very cold weather, which is often when deer are feeding most heavily on plants needing protection.