Deer have a very sensitive sense of smell and rely heavily on it. There are two strategies to deter deer through scent: jamming their sensors and setting off a red alert. Scent deterrents that "jam the deer's sensors" are so strongly scented that deer in their vicinity have trouble scenting through them. These scents don't necessarily have to be offensive to humans, just intense. Not being able to scent the wind for danger is an uncomfortable situation for deer, and they can't tolerate it for long.
"Red alert" deterrents offer a more direct approach and are more affective, when used properly, than masking scents. These are predator scents. Bear in mind that garden conditions may require frequent applications to keep repellent scents fresh and effective. Most need reapplication after a heavy rain, though humid conditions actually enhance odors. Don't forget that deer feed from ground level to as high as 6 feet and that repellents must be applied within that range.
Early spring applications protect the garden as new growth begins to emerge.
Scented soaps repel deer; leaving bars of soap about the garden scares deer away.
USAGE: Drill a small hole through each soap bar, tie with string, and hang about the yard or in tree or shrub branches. Leave the wrappers on to prevent soap from washing away. You can also place soap in cheesecloth bags or old nylon stockings. Some gardeners insist that heavily scented deodorant soaps are most effective. Avoid soaps containing edible oils such as coconut oil as deer may actually eat such soap!
PROS AND CONS
Hanging soap in the garden is fairly effective in preventing deer from browsing within 3 feet of the bar. One problem, however, is that the same soap fats that repel deer can attract rodents who may chew on the bark. To prevent rodent damage, combine the use of soaps with a rodent repellent.
Interplanting repellent plants with more-vulnerable species is a valuable technique. Heavily scented herbs, such as artemisia, lavender, Russian sage, tansy, and yarrow, as well as culinary herbs, including, thyme, tarragon, oregano, dill, and chives, often prove intolerable to deer. Planting chives, onions, garlic, and any related members of the onion (Allium) genus near prize posies helps to keep the latter from becoming deer snacks.
Fabric softener Strips
One of the cheapest and easiest repellents you can try is fabric softener strips, the kind you use in your dryer. The stronger the fragrance, the better.
USAGE: Tie or hang fabric softener strips in or near susceptible plants. Hang them at intervals of three feet (as recommended for soap).
PROS AND CONS
Fabric softener strips are easy enough to install. However, the strips quickly become waterlogged after a rain and must be replaced. Even so, they remain relatively inexpensive and are worth a try.
Also known as naphthalene, moth balls or flakes have long been used as area repellents. Gardeners report success in deterring deer, squirrels, and skunks, among other creatures.
USAGE:Put several mothballs or a handful of flakes into cheesecloth or old nylon bags and place about the garden.
PROS AND CONS
Though an old standby at repelling many pests, from insects to mammals, mothballs are not without their drawbacks. They are flammable, evaporate quickly (and therefore need frequent replacement), and are toxic to humans and pets. Inhaling the fumes can cause headaches, nausea, and vomiting. Restrict their use and carefully monitor the effects.
Hot Pepper Spray
Not only does pepper spray taste bad, but also the active ingredient in hot peppers, capsaicin, burns. It is so potent that sprays containing it can ward off attacking dogs and grizzly bears.
USAGE: Whip up a batch of super-hot sauce in a bucket or tub and spray wherever needed. Mix 2 tablespoons hot pepper or Tabasco sauce, 1 gallon of water, Vapor Guard or Wilt-Pruf, if desired, or substitute a tablespoon of liquid dish soap. Stir well. Such additives as Vapor Guard and Wilt-Pruf extend the life of the mixture, help it adhere to the foliage, and prevent drying out, but are not absolutely necessary if you don't mind frequent applications. Apply with a garden sprayer. Coating just those plants around the perimeter may stave off further exploration by nosy deer, or you may need to cover anything vulnerable.
Homemade hot pepper sprays are among the only taste repellents that can be used on crops. Don't apply just before harvest, and be sure to rinse foods thoroughly and test cautiously before eating any treated foods. Some plants may be very sensitive to hot sauce sprays. Test spray or dip a leaf or two in the concoction before dowsing the entire plant.
PROS AND CONS
Homemade sprays are cheap and effective, the only caution being that not only some plants, but also many pollinators, are sensitive to capsaicin. Homemade hot pepper sprays require regular reapplications after rainfall or overhead watering, unless you add an antidessicant sticking agent, such as the products mentioned above.
Soapy water, especially when laced with human scent, serves as another double deterrent to deer. It not only smells bad, but also tastes atrocious to deer, according to a Wisconsin gardener who suggested this solution to the gray water disposal problem.
USAGE: Save soapy bathwater or whip up a fresh batch of soapy water from bar soap. Spray on the foliage of vulnerable plants. Since some plants are sensitive to soap, be sure to test spray a patch before fully treating.
PROS AND CONS
Though this approach has not been thoroughly tested, the reporting Wisconsin gardener claims total success using his sudsy solution. Gray water offers the additional advantage of being free, the basis is reasonable (deer are repelled by soaps) and it can't do any harm. Drawbacks include the fact that you have to respray after a good rain or two. Also, soap leaves an unattractive whitish film on foliage and can attract rodents. If mice or similar vermins are a problem in your garden, stir in a tablespoon of hot pepper sauce. Related commercial product is Hinder.
Systemic aversives, for lack of simpler term, are substances absorbed through the root systems of plants to make them taste bad. The best example, denatonium benzoate, is available commercially as No-Bite Tablets. Another formula, benzyl diethyl [2,6 xylylcarbamoyl] methyl ammonium saccharide and thymol (sold as Ro-Pel) has not performed as well as research trials.
USAGE: Bury one denatonium benzoate tablet near the roots of each plant to be protected. A single tablet should last from 1 to 3 years. Spray Ro-Pel over foliage according to the manufacturer's instructions. It can be used to protect nursery stock, Christmas trees, annuals, perennials, and shrubs.
PROS AND CONS
Although simple to use, safe, and non-toxic, denatonium benzoate tablets are not inexpensive compared to other taste repellents. A supply of 500 tablets rings up to about $275. As with other taste deterrents, the deer must sample the forbidden fruit before they learn the consequences. Though wonderful for ornamentals, this is obviously not an option for food crops.
Originally developed as a seed repellent, the fungicide thiram has proved quite distasteful to deer. It irritates mucous membranes in and around the mouth and nostrils. Be sure to check the label and follow the instructions regarding which plants this (and any other commercial) product can be used on. Never apply commercial products to food crops unless they are specifically labeled as approved for those crops.
USAGE: Mix 1 part thiram with 1 to 2 parts water and spray on susceptible plants. Be sure to spray up to a height of at least 6 feet.
PROS AND CONS
Although apparently very effective in reducing deer damage, thiram has a couple of drawbacks. First, you should use it only on plants for which it is registered. Second, it can be applied only to dormant plants, and only when temperatures are above freezing. In addition, it costs about $50 to the acre. Related commercial products are Chew-Not and Rabbit-Deer Repellent.