Pennsylvania State University
Berks County Cooperative Extension
Reprinted with permission from the Berks County Cooperative Extension
Over the past 30 years, especially the past decade, populations of white-tailed deer (Odocoileus virginianus) have increased dramatically throughout the Northeast and in many midwestern and western states. Increases in deer abundance can be attributed to changes in habitat, including reversion of abandoned farm fields to forest, and shifts in human population to rural and suburban areas. Both of these trends create open and forested habitat preferred by deer. In addition, decisions by landowners to prevent hunting have made many areas off limits to hunters, allowing deer populations to increase. Although the recovery of deer populations from only about 500,000 nationwide in the early 1900s to more than 15 million today is considered a wildlife management success story, many people increasingly view the situation with mixed feelings.
Habitat and Food Habits
Deer live on the forest edge rather than in continuous areas of mature forest. They prefer mixed conifer-hardwood forests, shrublands, and old fields with active cropland nearby. This rich mixture of vegetation produces abundant food and cover. Deer are very adaptable, however, and greater numbers are living in suburban neighborhoods, which have a combination of open lawn, succulent summer gardens, plentiful ornamental shrubs, and patches of forest cover.
Deer feed primarily on grasses, crops, leaves, twigs, and buds during late spring and summer. They forage on mast (e.g., beechnuts, wild cherry seeds, and acorns) during fall and concentrate almost entirely on twigs and buds during winter and early spring.
The amount of food that a deer must consume daily depends on its gender and body weight and the season. In general, deer consume 3 percent of their body weight each day. Therefore, a buck weighing 125 to 250 pounds requires from 4,000 to 6,000 calories each day, which can be obtained from 4 to 8 pounds of grass, forbs, and twigs.
Description of Damage
Home and Gardens - Deer frequently feed on flowers, fruits and vegetables, and the buds and twigs of fruit trees and ornamental shrubs. Damage to landscape plantings and ornamentals may occur at any time of year but is usually most severe in the late winter and early spring when other food supplies are limited.
Forests and Wildlife Habitat - Deer can also affect their own habitat and the abundance of other wildlife species. Overpopulation can profoundly influence the presence, absence, and abundance of plants and other wildlife. In many forests, over-browsing of tree seedlings creates open, park-like stands that have little or no vegetation near ground level. Instead of a diversity of woody and herbaceous plants, the ground surface may be dominated by ferns, grass, and woody shrub or tree species that are not preferred by deer.
Reduction of the understory and vertical structures, which gives forests a park-like appearance, removes important nesting and feeding sites for some forest songbirds. Nesting in more open forests can make bird eggs and nestlings easier for predators to detect. Some species may leave the area, whereas others will be less abundant than they once were. In addition, other wildlife, such as squirrels and chipmunks, must compete for acorns, a food preferred by deer.
Deer prefer certain plant species over others and frequently feed on economically valuable tree species, leaving less valuable trees. This change in species composition will have dramatic effects on our future forests and forest-related industries.
Deer feeding damage is readily distinguished from that caused by rabbits or rodents. Whereas rabbits or rodents leave a clean-cut surface, deer lack upper incisors and leave a ragged, broken end on browsed branches. Another indication is the height of the damage from the ground (up to 6 feet), which often rules out smaller mammals.
Population Control - Although repellents and fencing are the primary techniques used to address site-specific deer damage problems, these methods will not decrease damage on a community-wide scale. Deer populations will increase if mortality is low and food is abundant, and the population has the potential to double in size every two to three years.
Although the annual hunting season is an effective way to reduce deer populations and thus damage in rural areas, buck-only harvests cannot reduce or stabilize deer numbers. Where possible, landowners suffering damage should encourage or require hunters to harvest sufficient numbers of does (within the legal limits). Harvesting female deer is essential to reducing deer numbers and deer damage. In suburban areas where hunting may not be practical, some other form of mortality may be required to stabilize herd growth. Reproductive inhibitors are currently experimental and difficult to apply over large areas.
Deer Feeding Habits - Deer feed selectively on fertilized and unfertilized landscape plantings and managed croplands. Costly browsing damage may be reduced or eliminated by planting less preferred species or by establishing susceptible plants only in protected areas. A few strategies to consider include planting susceptible plants close to the house or in a fenced yard, or planting preferred species inside a protective ring of less preferred species. Under most circumstances, landscaping based on knowledge of deer feeding preferences provides an alternative to expensive chemical repellents and unsightly physical barriers.
Whether deer will target a particular plant species or variety depends on their previous habits and nutritional needs, plant palatability, seasonal factors, weather conditions, geographic area, and availability of alternative foods. Deer are creatures of habit, and previous movement patterns or foraging experiences can determine where damage will occur. Also, one plant species may be rarely damaged in one region of the country, but highly preferred in another due to differences in deer pressure and other factors. Examples of species with noted regional differences include holly, white pine, and deciduous magnolias. Therefore, caution must be taken when using plant preference lists from areas outside your own.
In general, damage from browsing is more severe when snow cover or extreme cold has reduced food availability. Another problem time is early spring when young succulent growth of ornamentals provides attractive browse before other spring growth is available. When food is in short supply, deer will browse even the most undesirable plants. Under such conditions, landscapers should combine damage control measures with careful plant selection. Damage control measures could include repellents, physical barriers (fencing), and deer population control. Ultimately, reducing the deer herd size is the most effective solution.
The lists in the boxes below, are from the publication "Resistance of Ornamentals to Deer Damage" by the West Virginia University Extension Service. The information derives from personal communications, published articles, and unpublished reports. Please note that deer-browsing resistance of a plant species changes according to fluctuations in deer populations, alternative food availability, and environmental factors. No plant is safe under all conditions.
Plants listed in the "Rarely Damaged" category are eaten infrequently by deer and are the best candidates for damage-prone landscapes. "Frequently Damaged" category plants often require physical or chemical protection. Before planting any of the species listed, check to ensure that they suit local climatic and soil conditions.
Scare Devices - A variety of frightening devices, including lights, whistles, loud noises, and scarecrows, have been used to prevent deer damage. Audio and visual scare devices are not recommended around the home or near urban or suburban areas, however, because of disturbance to neighbors, possible violations of noise ordinances, and lack of effectiveness. Deer habituate to scare devices after a few days of exposure.
Repellents - Repellents can help prevent deer from feeding on crops or landscaping plants and are most effective when integrated in a damage abatement program that includes one or more other techniques such as fencing and population management. Repellents are best for small orchards, gardens, and ornamental plantings around the home. Their utility is limited for row crops, forages, and other large acreages because of high costs, limitations on use, and variable results. Applying repellents prior to deer damage will help to prevent deer from establishing a feeding pattern.
Repellents fall into two broad categories - those that repel by taste and those that repel with a disagreeable odor. Most deer repellents can be applied as a spray to ornamental shrubs and non-bearing fruit trees. Hinder™, an ammonium soap-based repellent, and Deer- Off™, a product that incorporates putrescent egg solids, are the only repellents currently approved for use on garden vegetables and fruit-bearing trees during the growing season.
The effectiveness of repellents depends on the number of deer, feeding habits, and environmental conditions. If deer are very hungry and other food supplies are limited, repellents may not work. Some damage must be tolerated with the use of repellents, even if browsing pressure is low. Young trees should be treated completely. On older trees, treat only terminal growth that is within reach of deer (up to 6 feet above ground). Growth that appears after treatment may need to be sprayed again. Repellents should be applied when precipitation is not expected for 24 hours and temperatures will remain between 40°F and 80°F for that period. Research trials have shown that odor-based products usually outperform taste-based materials. No commercial repellent is 100 percent effective, and under heavy deer browsing pressure, the best materials must be reapplied about every five weeks. This may limit their use in areas that have deep snow and below-freezing temperatures during winter.
The deer repellents listed in Table 1 are grouped by active ingredient and include the type of plants for which they are registered. Product labels provide all necessary information on use and must be followed to meet legal requirements and achieve maximum success. The active ingredients are shown in parentheses after the trade names. "Home remedies" such as tankage, soap, bobcat urine, and human hair may act as repellents. However, because both state and federal regulatory agencies prohibit the commercial use of products not registered by the Environmental Protection Agency (EPA), we do not recommend them.
Table 1. Repellents
The table is an abbreviated form of Table 1 in the original document, which also includes: formulation, how to apply, length of effectiveness, cost and remarks.
Repellent Plants for which Registered Deer Away/Big Game Repellent™
(37% commercial putrescent egg solid)
Fruit trees before flowering; ornamental and Christmas trees Deer-Off Repellent Spray™
(3.1% egg solids, 0.0006% capsaicin, and 0.0006% garlic)
Flowers, grass, bulbs, ornamental shrubs, edible crops, plants, seedlings, trees Hinder™
(ammonium soaps of higher fatty acids, 13.8%)
Home gardens, ornamentals, annual and perennial flowers, fruit trees until one week before harvest Miller's Hot Sauce Animal Repellent™
Ornamentals, fruit and nut trees, bushes, vines, and hay bales stored in the field; can also protect vegetable crops if sprayed before development of edible parts Nott's chew-Not™
Dormant trees and shrubs Tree Guard™
(0.20% dentonium benzoate)
Shrubs, ornamental plants, conifers, and nonbearing deciduous trees; not intended for use on food or feed crops
Fencing - If deer densities are high, tolerance of damage is minimal, or particularly valuable plants need to be protected, fencing alone or fencing plus repellents may be the best option. Many different fence designs are available; the one you select may be based on cost-effectiveness, aesthetic considerations, or ease of construction.
Rope Fencing - A cotton rope fence used with a repellent is particularly useful for preventing deer browsing in flower beds or small vegetable gardens; this combination of a visual barrier and order repellent can reduce browsing considerably during the growing season when alternative foods are available. The fence can be constructed by installing 3- to 4-foot posts around the perimeter of the beds. Attach cotton cord or rope at a height of about 30 inches. Spray an odor-based repellent directly onto the cotton rope or strips of cotton cloth tied to the rope at 3- to 4-foot intervals.
Snow Fencing - Snow fences can be used during the winter and early spring to protect small groups of trees or shrubs. Although not an absolute barrier, a snow fence may effectively deter deer form entering small areas ( a circle 20 yards in diameter).
Plastic Bird Netting and Wire Cages - Plastic netting and wire cages can be used to prevent deer browsing of individual plants or small plantings. Both alternatives are inexpensive and can be aesthetically pleasing. Plastic netting can be wrapped around individual shrubs during the winter and early spring. The netting is usually invisible form a distance. Although deer my browse any portion of the plants that extends beyond the netting, damage is greatly reduced. Plastic netting can also be wrapped around clumps of flowers in early spring when other food supplies are most limited and deer are most likely to cause damage.
Rarely Damaged Trees Botanical Name Common Name Aesculus parviflora bottlebrush buckeye Amelanchier arborea downy serviceberry Amelanchier canadensis shadbush Amelanchier laevis Allegheny serviceberry Betual albo-sinensis Chinese paper birch Betula nigra 'Heritage' heritage birch Betula papyrifer paper birch Chamaecyparis pisifera Japanese false cypress Cryptomeria japonica Japanese cedar Picea pungens glauca Colorado blue spruce Pinus sylvestris Scotch pine Pseudotsuga menziesii Douglas fir Shrubs and Climbers Botanical Name Common Name Arctostaphylos uva-ursi bearberry Asimina triloba pawpaw Berberis spp. barberry Buxus spp. boxwood Caryopteris x clandonensis caryopteris (bluebeard) Calastrus scandens American bittersweet Cornus sericea red osier dogwood Cephalotaxus harringtonia var. horeana Japanese plum-yew Elaeagnus angustifolia Russian olive Gaultheria procumbens creeping wintergreen Hibiscus syriacus rose of Sharon Ilex x 'John T. Morris' John T. Morris holly Ilex x 'Lydia Morris' Lydia Morris holly Leucothoe spp. leucothoe Ligustrum vulgare European privet Pieris japonica Japanese andromeda Rhamus cathartica common buckthorn Sambucus canadensis blueberry elder Sarcoccoca hookeriana var. humilis dwarf sweet Christmas box Annuals, Perennials and Bulbs Botanical Name Common Name Achillea spp. yarrow Aconitum spp. monkshood Ageratum houstonianum ageratum Allium christophii star of Persia Allium neapolitanum daffodil garlic Allium ostrowskianum lily leek Anemone x hybrida Japanese anemone Anemonella thalictroides rue anemone Anethum graveolens common dill Aquilegia spp. columbine Aurinia saxatilis basket-of-gold Antirrhinum majus snapdragon Arabis spp. rockcress Arisaema thiphylum Jack-in-the-pulpit Aubrietia deltoidea rock cress Bergenia spp. bergenia Ceratostigma plumbaginoides plumbago Cimicfuga racemosa snakeroot Colchicum autumnale colchicum Colchicum speciosum colchicum Consolida amgigua larkspur Convallaria majalis lily-of-the-valley Coreopsis verticillata 'Moonbeam' threadleaf coreopsis Cyclamen hederifolium Neopolitan cyclamen Dicentra spectabilis bleeding heart Digitalis spp. foxglove Dryopteris marginalis wood fern Echinacea purpurea purple coneflower Epimedium spp. barrenwort Euphorbia spp. euphorbia Fritillaria spp. fritillary Galium odoratum sweet woodruff Gloriosa superba glory lily Hemmerocallis 'Stella d'Oro' Stella d'Oro daylily Hesperis matronalis dame's rocket Hyacinthus orientalis hyacinth Lamium maculatum deadnettle Lavandula spp. lavender Linaria vulgaris toadflax Lobularia maritime sweet alyssum Lychnis coronaria rose campion Matteuccia struthiopteris ostrich fern Narcissus spp. daffodil Nicotiana spp. flowering tobacco Osmunda regalis var. spectabilis royal fern Pachysandra procumbens Allegheny spurge Pachysandra terminalis Japanese spurge Papaver orientale oriental poppy Pelargonium spp. scented geranium Pervoshia atriplicifolia Russian sage Ranunculus spp. buttercup Rheum rhabarbarum rhubarb Rudbeckia spp. coneflower Salvia spp. sage Santolina chamaecyparissus lavender cotton Scilla spp. squill Stachys byzantina lamb's ears Tagetes spp. marigold Tanacetum vulgare common tansy Thymus spp. thyme Tiarella cordifolia foam flower Tropaeolum majus nasturtium Yucca spp. yucca
Frequently Damaged Trees Botanical Name Common Name Abies balsamea balsam fir Acer palmatum (red-leaf varieties) Japanese maple Acer platanoides Norway maple Cedrus atlantica atlas cedar Cercis canadensis redbud Chionanthus virginicus fringe tree Cupressocyparis leylandii Leyland cypress Fraxinus excelsior European ash Ilex 'Nellie Stevens' Nellie Stevens holly Kuelreutaria paniculata goldenrain tree Magnolia soulangeana saucer magnolia Malus spp. apple and crabapple Prunus spp. cherry and plum Pinus strobes white pine Pyrus spp. pear Thuja occidentalis arborvitae Tsuga spp. hemlock Shrubs and Climbers Botanical Name Common Name Chaenomeles japonica quince Clematis spp. clematis Cornus mas cornelian cherry, dogwood Euonymus alatus winged euonymus Euonymus fortunei wintercreeper Hydrangea quercifolia bigleaf hydrangea Hydrangea quercifolia oakleaf hydrangea Ilex comuta Chinese holly Ilex x merserveae messerve holly Ilex verticillata common winterberry Kalmia latifolia mountain laurel Rhododendron austrinum Florida azalea Rhododendron periclymenoides pinksterbloom azalea Rhododendron vaseyi pink shell azalea Rhododendron hybrids evergreen azaleas and rhododendrons Rosa hybrids hybrid roses Rubus spp. blackberry and raspberry Sorbus aucupatia European mountain ash Syringa patula Manchurian lilac Taxus spp. yew Vaccinium corymbosum highbush blueberry Annuals, Perennials and Bulbs Botanical Name Common Name Aegopodium podagaria bishop's weed Aquilegia spp. columbine Athyrium niponicum var.pictum Japanese painted fern Cherianthus spp. wall flower Hedera helix English ivy Helianthus spp. sunflower Hosta spp. hosta Hemerocallis spp. and hybrids daylily Iberis sempervirens candytuft Lilium spp. lily Matthoila incama stocks Pelargonium spp. geranium Polygonatum biflorum Solomon's seal Ranunculus asiaticus buttercup Trillium spp. trillium Tulipa spp. tulips Vinca minor periwinkle Viola spp. pansies and violas