Deer, Deer, Deer!

Deer populations have increased in recent decades, impacting human health, forests, agriculture, and, of course, our gardens.  Unless you’re new to the area or new to gardening, you’ve probably been dealing with the “deer munch” for a while.

How to Protect Gardens and Landscapes from Deer Damage

Let me be candid.  The title of this section is quite the misnomer.  I wish I were announcing a breakthrough in deer repellents or deterrents; I’m sorry, but I have no such news.  There are still no sure-fire protective measures against deer damage to your landscape, especially if you live in a suburban or rural area —  with the exception of fencing.  Due to the expense and appearance of fencing, most of us would prefer an effective repellent or deterrent.  As you’ve probably already discovered, a repellent or device that works initially may become a failure over time as the newness fades and deer adapt.

Whether or not a particular plant will be eaten depends on the deer’s previous experience, nutritional needs, plant palatability, seasonal factors, weather conditions, and the availability of alternative foods.  Deer are creatures of habit, with good memories and the ability to learn from each other.  Also, deer behavior varies by region; in other words, the deer in our region may behave differently from those elsewhere.  This fact probably explains why a repellent spray or device might work well in one area, but not in another.  Weather is a major factor; deer browsing increases in extreme weather such as drought or extreme cold.  In summer, there may be more of their favorite forbs available, so you may see less damage than in winter;  in summer, repellants, scare devices, or temporary fencing may provide satisfactory protection.   In winter, deer become more desperate for food, so the munch on your landscape shrubs and trees generally increases.  This is especially true for shrubs —  and especially for the evergreen shrubs.

Once deer become accustomed to feeding in an area, they will likely continue.  It is easier to prevent them from developing the habit in the first place. Well, this advice comes too late for me and my plants, but it’s worth knowing.  If you are fortunate enough to be seeing deer damage for the first time, take immediate action to discourage and prevent deer browse.

The experts say it’s best to try several different strategies to find out what works best in your yard, and that most strategies are more effective when you employ several together.

Was it a deer or a rodent?  

Before you adopt a deer strategy, try to make sure it’s truly a deer that’s doing the damage.  Last summer my zinnias were chewed badly, something that had never happened before.  Of course, my initial suspect was deer. But it’s not always easy to identify the culprit, especially now that deer seem to be eating plants they’ve never touched before.  Looking closely at the damage can help. Deer do not have upper incisors, so they grasp and tear leaves and branches, leaving a rough and torn appearance. If you’re seeing a neat cut at a 45° angle, the perpetrator is more likely a rabbit or other rodent, especially if it’s low to the ground.  Rabbit tooth marks are about the width of the tip of a spoon, while other rodent tooth marks appear to have been made by the tine of a fork.  Look for droppings, too, form and texture can be a helpful clue.

Deer resistant plants?

Can you modify your landscape to reduce deer browsing?  Yes, but only to a limited extent.  Try placing your most vulnerable plants near your house and walkways; deer may even leave a rhododendron alone if it’s right next to a well-used door.  Another strategy is to surround deer favorites with more resistant plants, especially herbs whose odors seem to repel deer, such as mint, sage, nepeta, and the like.

As we’ve learned to our sorrow, there’s no such thing as a deer-resistant plant, but there are plants that are far less likely to be heavily damaged by deer.  Most gardeners know that fuzzy and prickly plants are not favored by deer, nor are the smells of most herbs.  And you’re probably familiar with those lists of deer-resistant plants.  Perhaps you’ve “talked back” to such a list after spotting a “deer-resistant” plant that has been devoured by deer in your garden!  At the risk of setting off a round of howling, here’s a recently-updated list of plants that deer are less likely to munch:

—Cornell Coop.Ext. Tompkins County/Gardening with Deer Q & A, 202  ( I’m adding my own howl right here and now:  my camassias have been chewed heavily by some critter or other, maybe deer, maybe rabbits. In any event, this wonderful bulb needs protection.  For more about camassia, see Camassias/The Garden Shed.

While this list includes some native species, did you notice that the plants listed are mostly non-natives? That is because deer prefer native plants, probably because they co-evolved together.  For those of us who are trying to include more natives in our gardens, this presents a major conundrum.  Some experts say that our local experiences are probably the best guide in identifying deer-resistant plants.  With that in mind, I’ve pulled together a list of natives that have avoided the browse in my yard.

Natives that deer avoid in MY gardens:

• swamp milkweed (Asclepias incarnata)
• blue mistflower (Conoclinium coelestinum)
• bottlebrush buckeye (Aesculus parviflora)
• wild bergamot (Monarda fistulosa)
• ragwort (Packera aurea)
• blue star (Amsonia hubrichtii)
• Annise hyssop (Agastache sp.)
• native holly (Ilex opaca)
• mayapple (Podophyllum pedantatum)
• beebalm (Monarda didyma)
• many grasses, sedges, and ferns

My experience may not be of much use in future gardening seasons because if deer are hungry enough — and the deer around here appear to be starving — they will start eating plants they never touched in the past.  After years of ignoring it, deer suddenly started eating my goldenrod, so I now understand how a list becomes obsolete. But let me know which native plants are deer-resistant in your yard, and we can develop a highly focused local list.

In my research, I have located several lists of native plants that deer avoid in our region:

• Deer Resistant Native Plants for the Northern Neck/ Va. Native Plant Society, Northern Neck Chapter
• Deer Resistant Native Plants/Univ.Md.Extension
• “Selective Planting Recommendations for Deer Management,” Pest Management Guide 2020/Va.Coop.Ext.  (Section 8-6)
• “Deer Resistant Plants Recommended for Central and Southeastern NC Landscapes,” North Carolina Coop.Ext. (2015)

There’s one other list worth mentioning here, and that is the often-cited list of deer-resistant plants created in 2003 by Rutgers University:  Landscape Plants Rated by Deer Resistance, which helpfully categorizes plants by their likelihood of damage, from Rarely Damaged to Frequently Severely Damaged. It is also searchable by type of plant and category of damage. Looking for a shrub that deer don’t like?  I’d start with a shrub search on the Rutgers list.  One downside of this list is its inclusion of a number of invasives.  A Pennsylvania township took the Rutgers list and pared it down to mostly native, noninvasive plants and choosing only from the categories of Rarely and Seldom Severely Damaged.  Since Pennsylvania is as overrun by deer as central Virginia and has a similar climate, this list may be of use to us local gardeners: Deer Resistant Plants/ Tinicum Township Guide for Stewardship of Natural Resources, p. 19.  After studying all these lists, I’ve compiled a list of the more common native plants that are rarely damaged in our region.

NATIVE Plants Rarely Damaged by Deer, compiled from regional lists:

Keep in mind that many popular natives like dogwood and redbud are fairly deer resistant even though they don’t qualify as “Rarely Damaged.”  When considering a native plant, it is best to cross-reference between the lists cited above.

To these lists, I would add a few other plants — nonnatives —  that have mostly avoided the deer munch in my central Virginia garden:  Deutzia (Deutzia gracilis),  cranberry cotoneaster (Cotoneaster apiculatus), Winter Jasmine (Jasminum nudiflorum), doublefile viburnum (Viburnum plicatum var. tomentosum) and rose campion (Lychnis coronaria).

Plant arrangements and landscape design could help reduce deer damage.  There’s a new book that employs a design approach: Deer-Resistant Design: Fence-Free Gardens that Thrive Despite the Deer by Karen Chapman (2019). I have not yet gotten my hands on it, but it sounds well worth a read. Meanwhile, there’s no denying that fencing is the only highly effective option available at the moment.

Physical Barriers and Exclusion

Fencing

Fencing is probably the only truly reliable way to exclude deer from gardens and landscapes, especially in areas of high deer density like ours.   Most vegetable gardeners would agree that fencing is essential if you want to eat any of the vegetables or fruits you grow.  Some herbs and onions — oh, and rhubarb, too —  can manage without fencing, but that’s about it.

An effective deer fence must be tall enough that deer won’t jump over it —  8′ is the standard.  A shorter fence can work if it’s supplemented — the most common addition being electrical wire, but be sure that’s not prohibited by a local ordinance or HOA rules.  Another possible addition is pictured above, a fence plus a shrub border, created by Pat Chadwick, a regular contributor to The Garden Shed.  As Pat explains, “The shrubs that I planted on the outer exterior of the garden serve two purposes: (1) They prevent deer from being able to see into the garden. Normally, deer will not leap into an area if they can’t see how large the area is or how to get out of it;  (2) They act as a double barrier. To leap over the wire fence, a deer would have to clear the 5-foot wide hedge first, and I don’t think a deer would be crazy enough to try to leap over that AND the fence.”

A Maryland gardener developed an intriguing addition to a shorter fence that he’s found to be highly effective:  wire threaded through the fence at angles, creating confusing optical issues for deer.  You can see how it’s done on this video: Low Cost Deer Fence Alternative/YouTube/U.Md.Ext.  Some gardeners have had success with the so-called 3D fence, which confuses deer with simple additional lines outside the fence.  To see how, watch here: 3D Deer Fence/YouTube. Remember that rabbits and other small mammals  can burrow under fencing, so it’s important to bury your fence 6 to 12 inches below ground.

For an excellent comparison of several types of fences, including some DIY varieties, watch this University of Maryland video — Fencing for Your Garden, — which compares materials, costs, and time required for each of the following kinds of fences:

— small, handmade, bird-netting 5′ fence, easy and inexpensive, using available materials

–vinyl-coated welded wire fence, designed to exclude rabbits and groundhogs

— polypropylene deer netting fence for a community garden

— solar-powered electric fence

— high-tensile wire fence, well-suited to slopes

Some of these fences are build-it-yourself projects, but due to the skill involved, building a high-tensile woven wire fence is usually best left to an experienced contractor.  High-Tensile Woven Wire Fences/Rutgers.edu.  For detailed instructions on how to build a plastic mesh fence, see How to Build a Plastic Mesh Deer Exclusion Fence/ Purdue Univ.Ext  .   You’ll find plans and specifications in several of the articles listed at the end of this article under SOURCES.

Micro-Enclosures are defined as small, fenced areas that create a psychological deterrent to deer, which apparently avoid entering small spaces that restrict quick entry and exit.  The University of Minnesota has supported research on micro-enclosures built by a Minnesota farmer/forest owner, who built six different enclosures out of cattle panels, which are typically sold at farm supply stores.  Over the course of two growing seasons, deer entered only one enclosure; apparently that enclosure was a bit too large because after its size was reduced, deer stayed away.

The report on this micro-enclosure research contains photos and detailed instructions for building a micro-enclosure, Protecting Plants from Deer/Univ.Minn.Ext.   I was intrigued by the fact that the University of Minnesota has created Regional Sustainable Development Partnerships which are supporting research on “practical tips for keeping deer away from plants,” because “landowners, gardeners and foresters need practical solutions for protecting plants from deer.”  Yes, indeed!  You’ll also find a research-supported recipe for homemade deer repellent at this site.

Wire cages, tree shelters, bud caps, netting and other structures :   Wire cages are usually effective in protecting a single plant; the cage should be at least 1.5 feet in diameter and three to four feet in height. Tree guards or shelters or tubes can protect seedlings and saplings until a tree is large enough to withstand some browsing.  Bud caps were news to me; they are simply squares of newspaper or cardstock stapled around the terminal buds of trees, usually conifers, during winter.

You might be surprised to hear that there is portable electric fencing on the market; it apparently works well for small areas and can be easily dismantled and moved to another location.  A 25′ X 50′ area can be set up in only one hour without tools.  Read all about it at Portable Electric Fencing/Rutgers.edu.

 

Wire cages and other enclosures are also effective in preventing damage to trees from antler-rubbing by male deer in the fall.  Get this protection in place by August and leave it there until the end of December.  To be effective, the cage should be at least 1.5 feet in diameter and 3 to 4 feet in height.  I’ve used fallen limbs — the pricklier the better — to create my own DIY protection against antler rubbing.  The good news:  it worked, at least this year.  I decided to try this approach to prevent summer browsing on my oakleaf hydrangea; A spiky native plum (Prunus americana) collapsed nearby, so I’ve hauled large branches into position all around the oakleaf hydrangea.  I’ll report on this experiment next fall.

Fishing Line and Paracords

Not up for building a fence or even a micro-enclosure?  Some gardeners have reported that by stringing multiple parallel strands of cords or fishing line, they’ve discouraged deer from entering their yards or garden area, though others have not had similar success.  Some friends tried this technique using thin ropes called “paracord” around the perimeter of the landscaped area of their yard; the deer stopped entering their yard for an entire year; they concluded that the lines caused the deer to shift their normal travel patterns.  Reader, I tried it myself!  I ordered paracord online and threaded parallel lines around the part of my landscape that’s full of cherry laurels and other favorites for winter browsing.  The result:  for the first time in years, the cherry laurels were not chewed down to their nibs.  Since my timing was off (i.e., late), the laurels had already been browsed to some extent, but overall, the damage was much less than in the past.  Will this method work again next year?  It’s a good question; deer tend to adapt to changes.  They’ve been known to adjust to human hair, soap, loud noises, and other tactics.

Horizontal barriers.  I thought I’d heard it all on the subject of deer exclusion, but then I read about horizontal barriers in a 2013 article by Michigan State University Extension.   A horizontal barrier operates on the same principle as cattle guards.  The cattle will not step on something that could ensnare their feet, and deer are like-minded.  To make your own horizontal barrier:

–Place concrete blocks on the ground.

–Unroll and slide chicken wire or woven fencing flat on top of the blocks.

–Set these barriers in a square or rectangle around those shrubs that deer love to eat. Be sure this “horizontal fence” is far enough from the shrub or sapling that a deer cannot lean over and nibble a branch.

According to Michigan State Extension, the deer will not step onto or into the “horizontal fence.” If the wire is chicken wire and they step on it, it will sink. If it is woven wire farm fencing, they cannot place their feet into the holes to walk in.  You can achieve the same effect with concrete blocks and old farm gates. Deer versus your Landscape/Mich.St.Ext..

Deer Repellents

Most gardeners are familiar with the basics about deer repellents:  they work on either bad smells or bad tastes, they have to be reapplied OFTEN and AFTER EVERY RAIN, and changing the formula regularly improves effectiveness.  Some experts say that the most effective repellents contain ingredients that are BOTH bad tasting and bad smelling, and that repellents are more effective in reducing winter browse than summer browse.

Most repellents on the market are intended for ornamental plants, but a repellent made of ammonium soaps of higher fatty acids is registered for use on edible crops — but only prior to the development of edible parts.  Cornell Coop.Ext./Monroe County.

If you want to make your own repellent, check out the recipe for a tested odor-based non-winter repellent at Protecting Plants from Deer/Univ.Minn.Ext..  This DIY repellent should be reapplied every two weeks and after heavy rain.  And as all the experts agree, if deer are very hungry and deer pressure is heavy, deer will likely “override their aversion” and munch anyway.

Some research shows that predator urine, from bobcats and coyotes, is the most effective repellent in deterring white-tailed deer.  Non-lethal Deer Deterrents/City of Ann Arbor Deer Management.

Scare Devices

Another type of deterrent is a scare device, such as lights, whistles, loud noisemakers, scarecrows, and the like.  Some gardeners have reported success with motion-activated water spray devices and lights.  I read one article from an Extension office which indicated that wind chimes can be effective.  The bottom line is that deer tend to adapt to these deterrents, but if you’ve had success with one, please share it in the Comments Section below.  Before setting up a scare device, consider your neighbors, local ordinances, and HOA rules.

Some gardeners swear by dogs as the best possible deer deterrent.  A dog that stays outside at night can be very effective.  A related option that has “shown great promise in recent experiments” is the use of a dog contained by a buried electrical (“invisible”) fence. Cornell Coop.Ext..

Community Solutions

When deer start eating everything and our repellents no longer work, we may be wondering if there’s a macro-solution to the deer problem.  Allowing or increasing hunting is one option that a number of communities have tried; some of the most successful have been managed programs overseen by a municipality, often employing professional archers and sharpshooters and allowing hunting at night. To learn more about these community hunting strategies, see Arlington Regional Master Naturalists/”White-tailed Deer and Forest Health in Northern Virginia” 2020 (Arlington’s archery program has culled about 1,000 deer per year since 2014).  Hoping for a non-lethal option?  Well, at least one community has one:  Cincinnati’s Clifton Neighborhood Deer Fertility Control Pilot Program — well worth reading about.  Wildlife experts say that fertility programs have not been shown to be effective, or at least not as effective as hunting.

Personal Experimentation

Have you experimented with your own deer deterrents?  If so, we’d love to hear from you.  Last fall I tried “planting” onions (the chef’s rejects) near my asters, a known deer favorite, and at least in the short term, it’s working. I’ve also  been known to scoop up the leavings after chopping onions for dinner, rush out the door, and then scatter them in my garden!

Impact of Deer on Human Health and Forest Health

Tickborne Diseases:  Deer clearly play a major role in the spread of Lyme disease, which is a growing and geographically-expanding health problem, as are other tickborne diseases. According to one recent research report, “There is broad consensus that the white-tailed deer is a main driver for the remarkable increase in I. scapularis ticks in the northern parts of the eastern United States over the past 40 years.”  Stemming the Rising Tide of Human-Biting Ticks and Tickborne Diseases, United States/ncbi.nim.nih.gov. We gardeners are painfully aware of this problem; I’m sure I’m not alone in spraying insect repellent on my ankles and pulling socks up over my pants every single time I head out the door to my garden.  But there are other potential health problems looming.

Chronic Wasting Disease:  You’ve heard the scary talk on the news about “the next pandemic,” right?  Well, some scientists are issuing strong warnings that the next disease that could jump from animals to humans might be chronic wasting disease (CWD), a fatal disease of deer similar to mad cow.  There’s no denying that CWD is rampant among deer in several regions of North America.  To learn more about this threat, read “Experts Call for Action on Chronic Wasting Disease,” Center for Infectious Disease Research & Policy, Univ.Minn.

CWD was first detected in Virginia in 2009, and has been identified in Fauquier, Frederick, Clarke, Culpeper, Loudoun, Madison, Rappahannock, Shenandoah, and Warren counties. CWD is caused by abnormal infectious proteins called prions, which can pass between deer through saliva, feces, urine, and through water or soil contaminated with prions; if these prions could be in the soil where we work, gardeners can’t help being concerned.   The Department of Wildlife Resources is responsible for tracking the spread of CWD among deer and elk, and the disease seems to be spreading rapidly into our region, with the first ever cases detected in 2020 in Rappahannock, Warren, and Madison counties.

Forest Health:  It’s not just our gardens that deer are decimating. They’ve caused major damage on farms and orchards, but the newest concern is forest health, especially as deer populations have ballooned and exceeded the “biological carrying capacity” of the land in large parts of North America.  Research indicates that deer can adversely affect forest ecosystems (Ramirez, Jansen, & Poorter, 2018).  Because native plants are apparently tastier to deer, a deer herd can reduce the number of native understory shrubs and forbs, and thereby enhance the success of invasive plants (Rodewald & Arcese, 2016).  Some scientists have concluded that deer browsing on saplings and seedlings hinders forest regeneration, while others consider climate change to be the primary culprit. But the jury is still out on these issues, and most scientists agree that much research remains to be done.

Due to the multi-pronged impact of our large deer populations on gardens, farms, forests, and health, we gardeners have more than one reason to take an active role in advocating for effective public management of deer herds, along with heightened vigilance and controls against CWD.  For that reason, it’s worth noting that the Department of Wildlife Resources is in the process of amending regulations related to deer hunting and the spread of CWD, and that the public comment period is open now and until May 10.  DWR/virginia.gov/Proposed Hunting Regulations (“CWD monitoring data suggests a recent amplified spread of the disease to new areas of northwest Virginia,” so an expanded season for doe-hunting is proposed, among other tools).

SOURCES:

Featured Photo:  Urban deer by Michael B., CC BY-NC-ND 2.0, Flickr.com

“Deer: A Garden Pest,” vtechworks.lib.vt.edu/HORT-62 (2013)

“Selective Planting Recommendations for Deer Management,” Pest Management Guide 2020/Va.Coop.Ext.  (Section 8-6)

“Deer Resistant Plants Recommended for Central and Southeastern NC Landscapes,” North Carolina Coop.Ext. (2015)

“Gardening With Deer,” Penn.State Ext./psu.edu (updated 2017)

“Reducing Deer Damage to Ornamental and Garden Plants,”  Cornell Coop.Ext./rev. 2018)(comprehensive discussion of fencing and list of resistant plants)

“Managing White-Tailed Deer in Suburban Environments: A Technical Guide,”  DWR.virginia.gov           (Cornell Cooperative Extension, the Wildlife Society– Wildlife Damage Management Working Group, and the Northeast Wildlife Damage Research and Outreach Cooperative, 2000) (Detailed and extensive coverage of most issues)

City of Ann Arbor/Non-lethal Deer Deterrents (“Field trials of various scare devices indicated that deer can become habituated to them after a week of exposure to them. Trials of various scare devices have produced variable results.”)

“Managing Deer Damage in Maryland,” Univ.Md.Ext.  (Extensive coverage of deer issues and detailed fence plans)

“Garden Wars: Dealing with Deer,” Rutgers Master Gardners

“Deer Management Strategies,” Digital Repository of Univ.Md

“Forest damage by deer depends on cross‐scale interactions between climate, deer density and landscape structure,” Journal of Applied Ecology (Apr. 2020)

“White-Tailed Deer,” Penn State Ext. psu.edu

“History, Biology, and Management of White-tailed Deer in Virginia,” Va.Dept.Wildlife Resources/virginia.gov

Will Culling White-Tailed Deer Prevent Lyme Disease? NCBI/NIH.gov (Some research has tied the rise in Lyme disease to the increased deer population we’ve experienced, but as one scientist concluded, “Robust evidence linking deer control to reduced human Lyme disease risk is lacking.” )

Stemming the Rising Tide of Human-Biting Ticks and Tickborne Diseases, United States/ncbi.nim.nih.gov. (“fierce debate continues about the specific thresholds required to be reached for either deer reduction . . .or topical treatment of deer with acaricides . . . to suppress I. scapularis tick populations to the point where we also see an effect on human tick bites and tickborne diseases.” )

https://extension.umd.edu/resource/deer-damage

Does white-tailed deer density affect tree stocking in forests of the Eastern United States?. Ecol Process 8, 30 (2019)

Red oak seedlings as indicators of deer browse pressure: Gauging the outcome of different white‐tailed deer management approaches. Ecol Evol. 2019; 9: 13085– 13103.