Barriers

• Perhaps the most effective way to deter pests from entering and damaging your garden, fencing is also one of the most expensive. If your garden lies within deer habitat, fences should be at least 8 feet tall, as deer can jump up to 12 feet. A lower fence can also deter deer if it's slanted outward at a 30-degree angle or electrified. If you prefer a living fence, plant dense, thorny shrubs that grow at least 6 feet tall, such as Russian olives, hollies or hawthorns. Rabbits can dig under fences, so use small mesh and pin the bottom down, or dig it at least 2 inches into the ground to place the fencing. If smaller rodents, such as rats, are the issue, create barriers using glue boards on the ground, place traps on top of fences and walls around the garden, and put guards around gutters or pipes near the landscaping.
  
  

Remove Habitat

• If rodents are attacking your garden, remove their homes and hiding places. Many species of vermin nest in dense shrubbery or vines, so keep plants well-pruned and immediately remove dead branches and foliage. Ignite smoke or gas cartridges inside of rat, squirrel or rabbit burrows; the noxious fumes will drive them out. If deer are the problem, keep the areas around the garden free of large, overgrown shrubs and trees that provide cover.
  
  

Noise

• A barking dog deters many vermin, especially deer or raccoons, but isn't foolproof, especially if the dog is tied or inside. Some nurseries sell alarms or cannons that repel deer, but they often grow used to the noise and ignore it. Cheaper options include hanging pieces of wood or aluminum plates where wind makes them strike each other. Similarly, ultrasound or high-frequency noise rodent repellant devices may work for a while, but once the animals grow accustomed to the noise they ignore it.
  
  

Repellents

• It's hard to get rid of rats once they're established.NA/AbleStock.com/Getty Images
  
  Nurseries sell commercially prepared repellent formulas that either smell or taste bad to deer and rabbits. Some contain the urine of predators, such as coyotes, mountain lions or wolves, while others are based on bitter, spicy or putrescent tastes or smells. Repellents are most effective when a variety of smells or tastes are used. Make your own repellents by placing human hair, deodorant soap or moth balls in mesh bags and hanging them around the garden or by spraying a mixture of beaten eggs and water on non-edible plants. Rabbits are also deterred -- at least for a while -- by ammonium-based soaps. Rats tend to ignore smelly or bad-tasting repellents, but moth balls may deter them.
  
  

Unattractive Plants

• Though rats and squirrels aren't deterred by specific plants, deer and rabbits tend to avoid species with certain characteristics. Plants with gray, hairy foliage; spines or thorns; pointy or rough leaves; bitter tastes; pungent smells; or thick sap discourage deer and rabbits. Plant a few species with these traits among your flowers to deter hungry vermin.