The average garden plant is typically chosen for its appearance or its usefulness in cooking or medicine. For the most part, such plants have little in the way of self-defense mechanisms to prevent them from becoming prey to any hungry passing herbivore. With that being said, there are a number of plants that can be introduced to your garden, both as animal deterrents and for their own properties, as well.
Lungwort (pulmonaria) is a small flowering shrub that was once thought to treat lung disorders. It grows well in the wet, temperate climates common to much of Europe and western Asia. Russian Sage is a hardy plant with small flowers and long, woody stalks that can grow up to 5 feet in height. It can withstand heat, cold and drought well and provide a spicy alternative to regular sage. Catmint (nepeta) is a low-clinging creeper that produces lavender and white flowers and gray foliage. This is useful in teas and bath mixtures, as well as for entertaining cats.
Foxglove (digitalis) is a species native to most of Europe that produces a single long stem and small pale green leaves. The flowers it generates on its second year are normally purple or blue, arranged in a spiral pattern around the stem and look like little bells. The presence of digitoxin in this flower can cause cardiac arrest and death in human beings and all known animals. Rose campion (lychnis) is an evergreen with felt-like leaves common to wet American temperate zones. Each stalk is tipped with an umbrella-like flower of striking rose red and the entire plant produces a mild irritant, which most animals avoid.
Licorice vine (petiolare) is a soft shrub with low, dense foliage and creamy flowers that does well in temperate climates and full sun. The leaves contain a natural insect repellent and are often steeped for a tea believed to treat asthma and bronchial issues. Flowering tobacco (nicotiana) grows in full sunlight in tropical and subtropical climates. The nicotine the leaves contain are a natural insecticide, which most animals avoid. The castor bean plant (ricinnis) is a tropical plant native to Africa with normally eight bristling leaflets of pale green or bright red situated around a central stalk. The juice of the plant, as well as the castor beans it produces, are toxic to all living creatures, including humans. While beautiful, this plant should only be used in gardens where no children are likely to wander.