Deer Resistant Plants and Deterrents Minimize Damage

Billings Gazette, Montana, U.S.A.
Sunday, October 26, 2003

By Rita M. Brehm
For the Billings Gazette
Deer in the city limits and outlying new developments present an increasing challenge to the gardener.  Initial selection of landscape and garden plants that are more resistant to deer, may provide the best remedy to deer damage, Jim Knight, Extension Wildlife Specialist for Montana State University, suggests.  “Think in advance when you plant,” he said.  “People want rose bushes and other exotic plants.  They might be a delicacy for the deer or other animals.”

“So keep in mind you could be welcoming them into your yard, vs. repelling them,” he said.  “In the whole natural balance of things, if the deer are hungry, they’re going to find the food.”

While deer in the garden is not a new issue, the problem is increasing not only in Montana, but also throughout the country.  “The deer herd is growing,” Knight said.

“A number of mild winters have resulted in greater fawn survival.  With the drought we’re in right now, the deer are looking for the more succulent yards and irrigated areas,” he commented.  Since they’ve adapted to the urban lifestyle, fawns are born there, and the urbanized fawns will bring their offspring back to the gardens and yards.

Two information bulletins, (Montguide 9521 AG, “Deer-resistant Ornamental Plants” and Montguide 9841 AG, “Minimizing deer Damage to Residential Plantings,”) are available from the University of Montana Extension Service.  They offer tips to minimize deer damage and a list of deer resistant flowers, ground covers, shrubs and trees (See list in sidebar story).  But keep in mind that hungry deer will eat things they normally would resist in better conditions.  “That’s why we use the term resistant,” Knight added.  He said starving deer might even eat unsavory things such as junipers.

In researching deer problems, Vicki Thomas, certified plant professional with Gainan’s Heights Garden Center, said she discovered estimates indicating the deer population has tripled in the U.S. since 1985.  From Florida to Pennsylvania to Wisconsin to California, states throughout the country are experiencing similar problems.  “I’m constantly getting information from back East, where they have huge problems with urbanized deer,” Knight said.

It’s not difficult to tell if a deer has been browsing in your yard. Thomas remarked that the way deer chew is damaging, and that this time of the year they’re also going after bark on trees, for more roughage.  Deer lack upper incisors.  Their bottom teeth meet a tough upper pad on the top of their mouth.  As a deer browses, it grabs a mouthful of food and quickly pulls its head to the side to tear the food free.  Hence, you’ll find a jagged or torn surface on twigs or stems that they browse.  Other animals like rabbits will clip the plants off with a clean bite.

And indeed, when homeowners complain about deer, rose bushes are often mentioned.  Deer nip the buds and the flowers, and in winter, they eat the bushes as well.  In addition to planting tolerant plants, harvesting garden crops as early as possible reduces the period of vulnerability to deer. Planting susceptible crops as far as possible form wooded cover will also reduce deer damage.  However, some homeowners find deer or antelope grazing on the petunias, rose bushes and other succulent favorites on their back porch.

Other options homeowners use to help minimize deer problems are repellents and fences.  Knights said that fences do not always have to be high to serve as a deterrent.  While many books suggest eight-foot fences, he said shorter fences, and electric fences could help dissuade deer from making a visit.  He’s had food luck keeping deer out of haystacks with four feet of net wire fence and another 18 inches of two strands of wire.  “It’s more of a visual barrier than anything else,” he said.  “Some people have luck with four-strand electric fence around the garden.”  He pointed out that it’s usually necessary to put up the hot wires before the garden starts growing.  Baiting the fence with peanut butter on aluminum foil that’s been taped to the fence with adhesive tape, or molasses are always ways to help the deer experience the current in the fence.  If they touch it with their tongue or nose, they get full voltage, and will likely decide to browse elsewhere.

Deer can clear low fences by jumping them, but sometimes it’s enough to deter the deer and send them elsewhere to find food.  Thomas noted that it’s important to keep the browse line in mind when applying deterrents or building fences.  Author Rhonda Massingham Hart, in her book, “Deer Proofing Your Garden,” describes ways to build fences, including one build at a 45 degree angle, so that the combined width and height will present a barrier the deer cannot clear.

Knight said there are many types of deer repellents on the market, that either rely on bad taste or smells that scare away deer.  He said the taste repellents that use thiram seem to work on shrubs and bushes.  The repellents based on smell have varying degrees of effectiveness in scientific tests around the country, since it sometimes depends on what else is available.  Bars of heavily perfumed soap strung around shrubs for instance, may deter deer if there’s another food source available.  There are many types of deterrents such as those using animal urine, or hot peppers or other bad-tasting ingredients.  The deer sometimes get used to the smells, or, if they’re starving, they may attempt to eat them anyway. However, those, along with dried blood, or blood meal, are spread around the plants, may wash off quickly if it rains, or because the area is irrigated.

Plantskydd Deer & Rabbit Repellent, developed for the forestry industry, is becoming a more widely used deterrent.  Don Doninger, who lives outside Livingston, is the area representative, and he offered insight into how the product works, and why it lasts up to six months during the dormant season.  The product was developed in Sweden, where they found a way to sterilize and pulverize dried blood so that it can be put into a solution of water, with a vegetable oil binder, he explained.  The product is now manufactured in the United States.  Plantskydd should be applied to dry plants, and it will become rainfast in 12-16 hours in this dry climate.  Of course, you need to keep your sprinklers turned off until it’s dry.  In more humid sections of the country, it needs at least 24 hours to dry.

The product repels deer and other animals based on its smell, he explained.  They think a predator is in the area, and that a kill has taken place, and they leave the area.  The more product you put out, the more likely they are to leave.  “If it’s wild, from a mouse to a moose, and it’s a plant-eater, it doesn’t like this stuff,” he said.

He applies the solution to apple trees and other plants, as well as the grass in winter, after the sprinklers have been turned off.  In winter, it should last six months, he said.  He sprays the trees until they’re red. “Make that plant red,” he emphasized.  “It has to last all winter.  The original color will return after about 18 to 36 hours.  It can be applied in winter, as long as the temperature is above freezing when it is applied.  Because it goes on red, it’s easy to see where you’ve applied it.  And, if you accidentally spray your concrete or deck or clothing, since it takes a long time to dry you can wash it off before it stains,” he said.  When applying to trees, it is only necessary to treat the area the deer can reach when browsing.

During the summer months, you’ll be required to apply the solution more often, since you’ll want to protect new growth, he pointed out.  And, plants under a sprinkler system may need to be treated more often. Plantskydd can last up to four months during the active growing season, Doninger said.  Keep in mind that the frequency of application is dependent upon the growth rate of the plant.  Apparently, petunias are a challenge because they are fast growers and they smell great.  He said he applies a lot onto the ground around them, but since the grass is mowed weekly, he treats it more often.  Other plants and flowers do not require the same diligence in application.

Another way to use the deterrent is to soak household sponges in the solution and suspend the dried sponges around your orchard or other plants that you want to protected.  You can also toss the small sponges into garden sheds or tack rooms, in order to clear out mice.  Once they’ve evacuated, he recommends spraying the perimeter to prevent them from returning.

As for the reason the product continues to work, year after year, Doninger said, is because you’re not introducing a new taste or smell to the deer. “When they smell blood, they think there has been a kill — a predator. This is not new to them, they just don’t like it.”  There are times, such as during the rut, that deer may be more difficult to drive out, Doninger said.  However, he said he consistently sprayed a quarter-mile grove of aspen trees along a creek, and used the saturated sponges, and finally succeeded in driving the deer out of the area.  He said that once the does leave, the bucks will follow.  Deer browse in a pattern, so you have to put on enough of the deterrent to break the pattern.  He noted that fawns also have not learned to fear the smell, and sometimes can cause damage before they follow their mother out of the area, once she is frightened away.  He noted that Plantskydd can also be applied to the ground or fences around haystack to deter deer or other browsers.

Deer Resistant Plants
By Rita M. Brehm
For the Gazette

Lists of deer-resistant plants vary according to area.  Your garden may fare better if you choose plants that deer do not like, but remember that starving deer are not particular about what they eat.  If they’re having a rough winter, or suffering from drought conditions, they’ll even eat things that are bad for them, Jim Knight, Extension Wildlife Specialist for Montana State University said.  Here is a partial list of deer-resistant plants:

Maples, Honey, Locust, Hawthorn, Oak, Birch, Ash, Douglas Fir, Bristlecone Pine, Colorado Blue Spruce, Austrian Pine, Mugo Pine, Canada Hemlock, Engelman Spruce.

Barberry, Juniper, Lilac, Mugo pine, Potentilla, Rubber Rabbitbrush, Spirea, Red Osier Dogwood, Mockorange, Fragrant Sumac, Common Buckthorn, Buffaloberry, Bridalwreath, Viburnum, Chokecherry, Currant, Elderberry, Gooseberry, Caragana.

Bittersweet, Clematis, Baltic Ivy, Honeysuckle.

Columbine, Astilbe, Tickseed, Bee Balm, Blackeyed Susan, Bleeding Heart, Campanula, Catmint, Purple Coneflower, Gaillardia, Gayfeather, Bluestem Joe-Pye-Weed, Cranesbill Geranium, Foxglove, Dianthus, Hellebore, Bugbane, Sunflower, Canytuft, Iris, Japanese Anemone, Lavender, Lupine, Monkshood, Pearly Everlasting, Penstemont, Peony, Poppy, Lungwort, Daffodil, Goldenrod, Speedwell, Yucca, Yarrow, Salvia, Russian Sage, Dedum, Shasta Daisy.

Ground Covers
Carpet Bugle, Lily-of-the-Valley, Periwinkle, Pachysandra, Lamb’s Ears, Lamium, “Silver Brocade” Artemisia, Snow-in-Summer, Thyme, Dead Nettle.