The deer population has increased in many areas in recent years, because we have eliminated most of their predators (wolves and cougars), but hunting is not allowed in residential areas. As the suburbs creep out further into rural areas more and more gardeners are having problems with deer. These large mammals can be a serious problem, not only because they can eat a lot of plants in a short time, but because they will keep coming back for more.
The 100% guaranteed way to keep deer out of the garden is with a fence, but to be effective it must be strong and high. If you are only fencing your vegetable garden it shouldn't be too difficult or expensive.
The cheapest commercial deer fencing is the eight foot tall plastic mesh. The 8 ft high metal wire deer fencing is stronger and more durable, but also more expensive.
Opaque fencing will also work and doesn’t have to be as tall as a transparent one, because deer (rather sensibly) won’t jump over something if they can’t see where they will land.
A double fence is also effective, if the two fences are far enough apart that they can’t clear both at once, but narrow enough that they can’t jump them singly. A variation on this is one fence, with a parallel strand of wire at the right distance out from it.
An aggressive dog will keep deer out of the garden, so long as it is free to roam and is there nearly all the time.
Image: Terry Spivey, USDA Forest Service, Bugwood.org