Repellent Companion Plants
Many plants will naturally control pests in your garden. It is possible to cover the scent of their favorite foods, use plants or extracts to annoy or kill pests, or even create physical barriers to keep insects away from your plants. You might even want to try using some plants that are said to repel vertebrate pests such as gophers, deer, and rabbits.
The chemical compounds created by strong-smelling plants
can discourage most pests. Bold perfumy or lemony frangeces can be found in
such plants as mints, thyme, lemon balm, and lemon geranium. Since many herbs
produce these compounds, they become natural choices for companion plants.
Mixing them in amongst pest-prone plants may just keep the pests guessing
where the food is.
Garlic has long been touted as a companion plant for plants that are prone to pests such as aphids and mosquitoes. But, it will also deter their natural enemies, the lacewings and ladybugs. There is some evidence to show that there may be some fungicidal and bactericidal properties to garlic which might help protect tomatoes and potatoes from blights. A garlic oil extract (Soak 3 ounces of minced garlic in 2 teaspoons of mineral oil for 24 hours then strain and add 1 pint of water and 1 teaspoon of liquid soap. Use at the rate of 1 to 2 tablespoons of the mixture in 1 pint of water and spray on the pests.) may be even more effective, but beware - it will kill the good bugs, too.
Since many of the destructive flying insects just ride the breezes, alighting wherever they find a suitable plant, you may be able to keep them from your plants by putting up a barrier of plants that they don't like. Block the prevailing wind with a fence, trellis, hedge, or screen. Use tall plants such as sunflowers or deciduous shrubs to screen your garden throughout the growing season. Planting evergreen shrubs and trees can block the wind year-round. These types of leafy barriers can also serve as shelter for beneficial insects.
It has been said that people are the only animals who enjoy
spicy or strongly aromatic foods. If that is the case, it should be possible
to discourage other kinds of creatures from turning your garden into a smorgasbörd.
Sound your garden with boldly scented or spicy herbs and vegetables for an
edging that you will enjoy, but animals won't.
Folklore and other sources have claimed that certain plants are especially good for repelling deer, rabbits, moles and similar nuisances. Planting the seeds of castor beans at 5 or 6 feet intervals around your garden is said to keep out moles and deer. Again, there needs to be a warning attached to this. Castor is toxic to children, and eating a few of the seeds has been known to be fatal. The mole plant (Euphorbia lathyrus) is said to repel mice, gophers, and moles. Some gardeners claim that you can annoy gophers by planting it next to their holes or by spacing plants every 5 feet around the garden as a barrier.
Unfortunately, with both of these, there is nothing that will necessarily stop the pest from just going around these unpleasant plants. Only a fence (8 feet high for deer, 2 feet high and 6 inches deep for rabbits, and 36 inches deep for gophers) will be more of a guarantee.