Protecting plants from deer

A micro-exclosure is a small, fenced compound for deer control based on the concept that deer avoid entering small spaces. Micro-exclosures provide a psychological deterrent to deer, appearing too risky for fast entry and exit.

With support from the Central RSDP, Wadena farmer and private forest owner Kent Scheer conducted trials on six micro-exclosures. Scheer built exclosures using cattle panels. Information presented on micro-exclosures here is based on Scheer’s trials.

Micro-exclosures can be used to protect plants in home vegetable gardening and reforestation projects. They work well for defining nursery beds, fencing berry plantings, protecting rare wild flowers, securing high-value plants such as ginseng, and supporting increased woodland diversity. Micro-exclosures can also be used in landscaping, providing simple, clean framing for a prized collection of hostas or lilies.

Over the course of two growing seasons (100 days), Scheer experienced only one breach in his pilot micro-exclosures. This was solved by reducing the size of the micro-exclosure. Once the area was made smaller, no further breaches occurred.

Micro-exclosures can be built using cattle panels commonly available at farming supply stores. The panels come in 16-foot lengths which can be carried by two people. They are rigid and self-supporting, but can be bowed to fit into the bed of a standard pick-up truck for transporting. Exclosures can be made of four cattle panels connected at the corners with cable clamps to form a 16-foot square. Other shapes and configurations can also be formed with fewer or more panels.

The top wire across the exclosures measures 50 inches from the ground. Three of the four corners are secured by cable clamps, and the remaining corner is left unconnected to serve as a gate. A total of nine ⅜-inch cable clamps are needed, with three in each of three corners.

Scheer recommends using four six-foot steel T posts with one wired to the center of each panel for increased rigidity.

Scheer’s 2018 trials indicated that an entire micro-exclosure could be built for approximately $150, with materials estimated at lasting at least 10 years. In his experience, micro-exclosures are easy to move around.

Micro-exclosures have shown a high success rate, but they should be monitored. Deer demonstrate regional differences in behavior, so it is important to observe whether the exclosure is effectively serving as a psychological deterrent. If a breach occurs, the exclosure can be made to appear smaller by installing a fifth cattle panel in the center or by stretching a wire hung with flagging across the midsection.

The Minnesota Department of Natural Resources offers a design and assistance for business-scale deer exclosures.

Mohr, C., and LaMond, A. (2018). Protecting our gardens from deer. RSDP Happenings. University of Minnesota Extension Regional Sustainable Development Partnerships.

Otten, J. (2018). A review of deer fencing and repellents for home gardens. Unpublished research conducted for a project of the University of Minnesota Extension Central Regional Sustainable Development Partnership.

Scheer, K. (2018). Summary evaluation of the three deer control systems. Unpublished research conducted for a project of the University of Minnesota Extension Central Regional Sustainable Development Partnership.

Repellents are another popular option for deer control. Commercial sprays can be effective when used according to directions, and a University of Minnesota research project identified a do-it-yourself (DIY) solution.

In 1994, Horticultural Science Professors James Lutz and Bert Swanson conducted a study comparing deer response to a variety of commercial repellents, methods of application, and levels of concentration. The study also included a simple home solution of eggs and water. They found the home solution - a recipe of 3 chicken eggs per 3.78 L of water - to be the most effective repellent. Variations on this simple solution have since become a part of gardening folklore.

1. Use a blender to blend three whole eggs thoroughly in water.

2. Pour the mixture into a container and add water to reach one gallon. Strain.

3. Spray the mixture onto new growth with thorough coverage using a hand sprayer or tank sprayer for larger amounts. Spray until leaves are wet and have a sheen.

4. Reapply every two weeks or after rain.  

The DIY egg spray offers a lower-cost alternative to commercial sprays and can be considered a reliable deer repellent for summer months when applied diligently.

A variety of online recipe variations of this basic formula can be found. However, gardening folklore is not always tested. The same University of Minnesota research demonstrated that adding secondary ingredients may mask the egg odor enough to reduce the spray effectiveness.

When using the DIY deer repellent, it’s important to be aware of its limitations and to understand deer psychology. Important considerations include:

• The repellent needs to be reapplied every two weeks or after a heavy rain.

• Desperate conditions or exceptionally heavy deer pressure may lead deer to override their aversion.

• Because the repellent works through deer’s sense of smell, the solution is not effective over winter and an alternative must be substituted.

• After extended use, deer may grow accustomed to the solution. To avoid this, gardeners can occasionally shift to a different odor-based formula or a formula with a hot pepper active ingredient.

• If the egg mixture is allowed to sit for more than a day, it develops an unpleasant odor. The longer it sits, the stronger the odor becomes. For this reason, it is best to avoid application on fruit or foodstuffs before harvest.

• At its richest, it can take a good scrubbing to remove the solution from hands and a warm wash to remove it from clothes. Gardeners may want to avoid spraying it near the house or in the yard before company arrives.

Even with these exceptions, this simple home remedy is estimated to cover 75% or more of an average gardener’s deer repellent needs at minimal cost. There may be commercial formulations which can protect longer, but the simple DIY recipe can be an excellent substitution if you run out, are not prepared at the beginning of the season, or want to save money.

Lutz, J. A. (1996). Comparative effectiveness of repellents for reducing deer feeding damage to woody and herbaceous plants in Minnesota. University of Minnesota. Master's thesis.

Lutz, J. A., and Swanson, B. T. (1995). Reducing deer damage to woody and herbaceous plants. Repellents in Wildlife Management Symposium, DigitalCommons@University of Nebraska - Lincoln, pp. 231–40.

Otten, J. (2018). A review of deer fencing and repellents for home gardens. Unpublished research conducted for a project of the University of Minnesota Extension Central Regional Sustainable Development Partnership.

Scheer, K. (2018). Summary evaluation of the three deer control systems. Unpublished research conducted for a project of the University of Minnesota Extension Central Regional Sustainable Development Partnership.