In part one (February 2010 issue, page 6), we talked about why the deer population has grown beyond the carrying capacity of our remaining natural areas and the effect this is having on forests. In this article, we will examine different methods people have tried to discourage deer from damaging gardens and forests.
Discouragement is sort of like installing an alarm system, deadbolt, and steel door: it won’t stop a determined thief, but it can make your property less inviting when compared to an easier target. Similarly, gardeners select less-appetizing plants, use repellents, and/or install fencing to encourage deer to move on to a more attractive property.
There are plant choices that deer do not ordinarily relish. These include perennials such as wild columbine (Aquilegia canadensis), butterfly weed (Asclepias tuberosa), and goldenrod (Solidago species). The spicebush (Lindera benzoin) is a shrub that deer really don’t seem to like; in fact, in some forested areas, spicebush is practically the only shrub left. However, as deer populations continue to increase, their preferred food becomes scarce. Starving deer (like humans in a besieged town) will eventually eat anything they can find. For lists of deer-resistant plants try the following links [some links have changed since originally published]:
Deer repellents include many different commercial products as well as a variety of homemade concoctions. (One can even purchase tiger poop or coyote urine.) There is little reliable data on the effectiveness of these commercial products, which can be very expensive to use and labor-intensive to apply. The results may depend on factors such as time of year applied, weather conditions, application rate, following exact label directions, and suggested reapplications. (Some products are supposed to be re-applied after rain.)
Maryland Cooperative Extension did test some commercial products, and published its results in Fact Sheet 810, which can be downloaded from the Home and Garden Information Center, https://extension.umd.edu/learn/publications/using-commercial-deer-repellents-manage-deer-browsing-landscape-fs-810 (also see https://extension.umd.edu/tags/deer-resistant). The Illinois Walnut Council also tested a number of repellents at a butternut reforestation site. While these were not scientifically replicated tests, they at least provide some comparative data. Results of their tests can be found at walnutcouncil.org/wp-content/uploads/2018/07/IllinoisDeerRepellentStudy.pdf.
There are plenty of colorful anecdotes recommending various home-made repellents. These include hanging bars of Dial soap or bags of human hair, sulphur/egg mixtures, hot pepper sprays, and garlic juice. (There are even gardeners who urinate around their yard’s perimeter to discourage deer.) The Walnut Council tests did include Dial soap.
It is probably too expensive and labor intensive to use repellents for an entire wooded area or even a moderately sized garden. And, of course, repellents are unlikely to discourage deer that are truly desperate for food. However, in situations where browsing is light and a gardener wants to protect one or two special trees for a couple of years, a repellent could be useful.
Exclusion fencing is one of the most effective techniques for protecting natural areas from browsing (as well as keeping bucks from rubbing the bark off saplings.) Once the deer are excluded, in many cases the forest begins to regenerate as saplings, shrubs, and herbaceous plants re-create the understory. Ground-nesting birds, salamanders, butterflies, and turtles once again have functional habitat.
However, deer have an amazing ability to jump. They can jump as high as ten feet (some sources claim 15 feet). They are also quite strong, able to push through holes or sagging fencing. Thus, the most effective fences are tall, sturdy, and expensive. Even the best fences, however, can be gotten around by determined deer which are habituated to humans.
When Brookside Gardens was first equipped with deer fencing and automatic gates, most deer were excluded. But some deer, which regularly fed in the gardens, figured out that people cause the gates to open. These deer would simply wait near the gate and dash through as soon as it opened.
Similarly, a friend in Chicago told me about deer living in a cemetery near her house. At night they jump over the wall and roam through neighborhood gardens, eating as they please. However, they do not jump back into the cemetery when they are done, because they are afraid of landing on a tombstone. Instead, they wait at the gate for the caretaker to open things up in the morning.
Still, exclusion fencing can be quite effective in areas with less human traffic. Naturally, there is a great deal of interest in finding less-expensive fencing options. The Cacapon Institute tested the effectiveness of solar-powered electric fencing. They found it does provide protection for newly planted trees. Read more at www.cacaponinstitute.org [study no longer available].
In our next installment, we will look at various population control strategies. ■Read Part 1: The Reasons Behind All the Deer Read Part 3: Population Control
© 2010 NFCCA [Source: https://nfcca.org/news/nn201004e.html]