dealing with deer in the garden, with brad roeller

WHILE MOST OF US focus on keeping deer from browsing our gardens, Brad Roeller actually once managed what was called a Deer Browse Garden as part of a 10-year research study to learn more about what these big herbivores do, and don’t do, when offered the opportunity—and how different strategies affect their behavior. Tips for gardening where deer are present is today’s topic.

Brad has held top horticultural positions at the Cary Institute of Ecosystem Studies in Millbrook, New York, at the New York Botanical Garden, and on a private estate. He’s currently a trustee at Innisfree Garden in Millbrook, where he’ll give a virtual talk on Wednesday afternoon, February 23, on effective solutions for dealing with deer.

Read along as you listen to the February 21, 2022 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here). (Photo of white-tailed doe and fawn grazing, above, by Raul654 from Wikimedia.)

deterring deer in the garden, with brad roeller



Margaret Roach: Hi Brad. I know this will be a popular topic for sure. So you actually had a Deer Browse Garden, which I love [laughter]. I just love the idea of that. Most of us are like, “No, no!”

Brad Roeller: Yeah. How would you like to design a garden for inviting deer into it? But yes, I did. I did. I’ll give you a brief background on it.

I started off working in 1972, at the newly formed Cary Arboretum of the New York Botanical Garden, which became the Institute of Ecosystem Studies. And working at an arboretum and having display gardens and things like this, obviously deer were always problematic in there.

So I’ve had to deal with deer for over 40 years in my career.

Margaret: Yes.

Brad: It’s always the top question that people ask, or one of the top questions, “What can they plant the deer won’t eat?” And that coincided with a lot of research that the Cary Arboretum and then the Institute of Ecosystem Studies was doing in wildlife management. We had some post-doctoral associates who specialized in whitetail deer management, and some biologists.

So basically there was a lot of work going on on deer, especially with their potential harmful effects on the environment. But I was more interested in their impacts on landscape. So out of that grew an idea to develop a garden which we can assess several things with deer.

And actually I was approached by, by Dr. Paul Curtis up at Cornell University, who had just completed—this is in the early 1980s—just completed his list, which categorized popular woody ornamentals for any inherent resistance to deer browsing. And this had been done at agricultural field stations around the state, in kind of nursery situations in there. He wanted to substantiate his work, and what was needed was assessing this inherent resistance in a more typical landscape setting.

Margaret: Right. So that’s where you came in.

Brad: That’s how it started. We were getting ready to landscape a large area. So traditional landscape design, but purposely interplanted in a landscape design were several different classes of vulnerable plants in there. I also wanted to do a few other things other than substantiate the work that Dr. Curtis had done.

By that time at the arboretum, I had come in contact with literally thousands of Asian and European counterparts of our North American trees and shrubs in there. And I’d noticed that in our woody collections or where we were evaluating them, several were resistant to deer browsing. So wanted to test a lot of plants that weren’t on any deer lists at the time.

Margaret: Right.

Brad: I also wanted to show homeowners what could happen if no protection measures were put in place in there. And then the biggest thing that I did was, in addition to evaluating individual plants, I also wanted to evaluate numerous methods of deterring deer through either spray-on repellents, scare devices and tactics, physical barriers, such as fencing and things like this. So I did that as well.

Margaret: Does scare tactics include going out and screaming at the top of your lungs [laughter]?

Brad: Yes. Well actually I had motion detectors, and I had AC/DC blaring at high volumes and things like this. But these are the things—motion detectors, scarecrows, all sorts of things like this. I even had a few people approach me, some chemical companies and entrepreneurs looking to do some efficacy studies on their either spray-on repellents or scare tactics. I had something I called the clapper, two pieces of wood which bang together, again motion detector, and things like this.

Margaret: Right. Right.

Brad: So this went on for about 10 years, Margaret, this evaluation. And I did annual surveys, periodic surveys to evaluate that, and collated all the information, and put it out to the public.

Margaret: So I know with your talk and, again, you’re going to talk about really how we’ve gotten to the densities of deer population that we have today, and how they affect our lives, how they affect the environment, which we were just referring to a minute ago. And then in the talk, I know you’ve told me comes the part that today’s listeners are eager for, some of the strategies, the tips.

Brad: Right.

Margaret: And so, I mean, I assume you use a… not counting on one thing, but more of a multi-layered strategy. I mean, as you said, you’ve a evaluated barriers, repellents, all kinds of things. So where do you usually begin? Like, do you ask people to look at like how heavy is their deer pressure before they pick a strategy

Brad: Yeah, it relies on kind of 11 different strategies, and I can quickly go through them.

Margaret: O.K.

Brad: Obviously starting with proper plant selection in there. And there’s hundreds. I bet I have hundreds of plant lists from state agencies, garden clubs, you name it, on deer-resistant plants in there. It’s important to remember that while they may have been effective in certain landscapes, what deer select in one landscape, they might turn their nose at in your landscape. So there’s a lot of other factors which I’m going to talk about briefly that comes into this. But start with those plant lists.

Margaret: If you have deer pressure, right?

Brad: Right. So when you’re looking to landscape or add new plants, that’s a good thing to have in your hip pocket. Obviously everybody knows that the gray foliage, the woolly or hirsute foliage, the aromatic plants, are all resistant and things like this. But as I say, I’ve seen landscapes where deer will not bother hostas or daylilies. And I’ve seen other landscapes where they’re just hammered in there. [Above, lamb’s ears, or Stachys byzantina, with woolly silver foliage; Wikimedia photo.]

Margaret: Sure.

Brad: So what I like to do is I encourage people to visit neighbors and gardens, public gardens and things like this. Gardeners love to talk about gardening, and they will be only too happy to tell you what, in your neighborhood, they have found that deer will eat. Because those deer will likely be your deer, if you will.

Margaret: So get localized insights.

Brad: That’s correct. That’s correct.

Margaret: O.K. Good; all right. We’ll start there.

Brad: One other thing. Just if we had to use strictly deer-resistant plants, it’d be a pretty dull landscape.

Margaret: Yes.

Brad: So I always tell people to plan on protecting vulnerable plants in there. And one thing that I started doing—and I have some anecdotal evidence, but I really didn’t do due diligence on evaluating this—is I’ve done several landscapes where I kind of front my beds, especially on the outside perimeters and things like this where deer are accessing, with highly resistant plants and site some of the more vulnerable plants in more interior sections.

However, that is something that I’ve seen work in some cases, but really no evidence to back that up with.

More importantly, the second tip is to become what I call a forecaster, both environmental and biological in there. I’m always looking at the size, health, and vigor of my local deer herd in my neighborhood, especially as the fall approaches. Several factors will influence that. When you have the perfect storm going into the fall season of prolonged summer drought, where the quality of the grasses and forbs is very poor; a very poor mast year (acorns and nut production and things like this); and then persistent snow cover. That’s the perfect storm for deer to take nontraditional food and they will eat anything to ward off starvation.

Margaret: They’re going to come visit our gardens for sure. Yeah.

Brad: Right. In the spring of the year, in the summer, when I’m driving around and I see the local deer in the fields and things like this, I’m noticing, “Hey, am I seeing twins? Or even triplets?” Is that normal doe with her two fawns that I’m seeing in the evenings now have additional deer in that group and things like this. So I’m almost looking at these kind of factors in developing my strategy.

Margaret: Right. O.K.

Brad: And right along that is what I call knowing the deer in your neighborhood. Where and when do you see deer on your property in there? Are they passing through, or do they seem to be around at all hours of the day and night?

Deer typically are nocturnal feeders. They will be getting off their beds in their safe areas, their sanctuaries, in the late afternoons and foraging in the evening and throughout the night, and then in the mornings heading back to their sanctuaries.

So when and where you see them—as you know, deer have traditional what we call deer runs, which they will move through areas and things like this. Know those in there and find out which ones they’re doing.

Deer are matriarchal. So knowing the deer, which ones are using your property is very important. And those are the ones that you have to upset, if you will, in there. One thing that will do that is anytime I’m doing new plantings, even though they might not be vulnerable or a time of year where deer will select it, I like to spray those new plantings with an odor-based repellent.

Deer are very curious by nature, and if their first contact with a new planting is a bad one, there is evidence to show that they will avoid it. So typically for the new plantings, I will spray them for the growing season to try to pattern those deer off that.

Margaret: Oh, interesting. Great tip.

Brad: Persistence [laughter]. Deer protection is a year-round thing. About the only month that there’s kind of a reprieve is the month of May when the grass is so green and succulent and high sugar content, that that’s what the deer are concentrating on. But you have to do this year-round.

There’s evidence that if you do this year-round and especially put up deterrents—odor-based deterrents, physical barriers on where deer are accessing your properties, those runs I mentioned—you can pattern those deer off your property over time.

And what really works good is what I call a neighborhood strategy. You know, I hate to see people put up deer fencing and then force those deer onto their neighbors and things like this. I’ve seen some cases where neighbors get together and develop a strategy that is very effective. And if persistent, you will pattern those deer off your property.

However, if new deer show up, and that’s why I say know the deer in your neighborhood, you may have to keep on that as well.

Margaret: Right. Right. So neighborhood or sort of collaborative efforts may be more effective.

Brad: Yes. Very effective. I’ve seen this done in homeowners’ associations and things like this as well.

Margaret: Now you said odor deterrents. So tell us, what do you mean by that?

Brad: Sure. With spray-on repellents, there’s basically those that are odor-based, and those that are taste-based. And recently in the last few years, they’ve been combining both odor- and taste-based repellents into one repellent in there.

So obviously during the warm-weather months, I do use spray-on repellents. I’ll use taste-based ones typically early spring, before the foliage, in there when they are browsing, and switch to odor-based ones when things are fully foliated. And it’s important to alternate whatever repellents that you’re using to keep them off-guard, to throw them a curve, if you will.

Margaret: Right. And if there’s new growth on a plant and you sprayed it in early spring, I mean the new growth isn’t going to be protected. Do you know what I mean? You have to really keep up with this.

Brad: That’s correct.

Margaret: So this is a commitment, right? Like you were talking about vigilance before.

Brad: That’s correct. And also bear in mind that flower buds, and things like lily scapes and rosebuds, don’t have the tissue to systemically take up systemic repellents so those will be vulnerable and things like this.

Margaret: Right.

Brad: So if you’d like, Margaret, I could give you kind of my seasonal strategy for protecting plants.

Margaret: Sure. I mean, that’s fine. Whatever you think—I mean, I’m a barrier or exclusion person. I’m a believer in keeping them out of here. But that’s my thing, and I’d love to know about some of the alternatives to the 8-foot fence, like a prison wall kind of fence. [Above, 8-foot posts between 4-foot picket fence panels hold 4 more feet of poly mesh for 8 feet of coverage at Margaret’s garden.]

Brad: Right, right. Yeah. Typically in early spring to protect your daffodils and early spring ephemerals coming up and things like this, I’m a big believer in Milorganite, a fertilizer—activated sewage sludge, which actually has its label now for food and crops there. I spread Milorganite as a topical fertilizer at hal- strength, recommended for turf, as soon as these bulbs start emerging. That will protect them in there.

About a month after that, I spread the second half, if you will, and that’ll get me through bloom period and into early spring. Importantly, if you’re using Milorganite as a deer repellent, I’ve seen lots of problems where they’re overusing it.

Margaret: Yes.

Brad: Don’t fertilize those beds again. They’re got it for the year. Some people also make up little sachets of Milorganite and hang them, and that works as well in there. But once we have full leaf expansion, I go to my spray-on repellents, typically alternating between odor- and taste-based ones.

There’s a plethora of them out on the market. I’ve evaluated them all. Some are a little bit better than others. But the important thing is none of the commercially available ones for homeowners, you’re going to get more than three to possibly four weeks’ worth of protection on plants. So you must reapply in there.

Margaret: Right.

Brad: I also like using some of the repellents that are actually fertilizers in there, like Bobbex and, oh, there’s some other ones—even Coast of Maine fermented salmon food is a great fertilizer, but also a repellent.

Margaret: How funny.

Brad: So when I’m looking for foliar feeds on roses or things like this, I might also use them as well.

Margaret: So you get like double-duty out of something that you needed anyway.

Brad: You get double-duty, right.

Margaret: O.K.

Brad: However, as the season winds down into late summer, early fall, I kind of develop my strategy for winter protection based upon those forecasts that I’ve seen. Size of deer herds, health, mast, summer drought, snow cover and things like this. And if the condition’s at perfect storm, I will definitely rely on physical barriers, deer fencing in there.

Margaret: Yes.

Brad: And if you’re smart and design your landscapes, I typically have galvanized metal pipe driven into the ground at grade level that accommodates 6-foot wooden stakes that has 6 -1/2-foor deer fencing or deer netting all labeled for the beds and things like this. So literally on a Saturday afternoon in late October, I can put up my physical barriers for the winter time and things like that.

Margaret: O.K. So you have buried into the ground, a piece of metal pipe that’s like a receptacle. It’s the female. And then you have the posts with the wire, the mesh, already attached to them, and then you roll that out and you stick them in.

Brad: Yep.

Margaret: That’s very interesting. So that’s a seasonal fence.

Brad: Right. Now for individual specimens out in the yard and things like this, I use just regular four foot snow fencing with posts, iron posts, substantially driven into the ground. It’s got to be rigid and strongly wired. There’s tips on the web on how to do this.

And if you have that perimeter about 18 to 24 inches from the furthest branches, if you will, that will work excellently. You’ll have 100 percent success in there. If it’s too close, they’ll find weak points. Or if it’s too weak, they’ll actually lean against it and start browsing on your conifers, or rhododendrons, or whatever you’re protecting. If it’s too far a perimeter, they’ll jump inside, browse, and then jump out in there. So that 18 to 24 inches seems to be the thing.

Margaret: And they don’t like to go inside what is perceived to be, even if it’s not from an 8-foot fence, barrier. Even a lower fence, like a vegetable garden if it had a fence, a 4- or 5-foot fence, it will look intimidating. They won’t want to jump in.

Brad: Right. Small areas, even small vegetable gardens, you can get away with a 4-foot fence, an electric picket, whatever you want. Larger areas where they can see across and things like this, they will jump that in there. So you don’t want to use low fencing for large areas.

Margaret: O.K.

Brad: Low fencing is for individual specimens or small areas.

Now for large areas, if you don’t want to go for the 7-1/2 or 8-foot conventional deer fencing, which a lot of people do, I’ve used what I call double perimeter fencing in there. Why the 4-foot works in small areas is the deer’s depth perception is a little bit suspect, so they’re quite not sure where they’re going to land when you have these smaller, lower barriers in there. So if you have something in your landscape, a picket fence, a stone wall or something that pretty much encircles your landscape, if you set another barrier on the outside of that or the inside of that, about 4 to 5 feet away, you accomplish this, throwing them off by the depth perception in there.

And I have done this with something as simple as monofilament, which they cannot see in there kind of throws them off. And I reinforce that by hanging some sachets or some scent darts with a really strong odor-based repellent or an essential oil, like oil of wintergreen. And I also cut some ripstop white nylon in the shape of a deer’s tail and hang a few of those on [laughter]. A deer when they’re alarmed will do a flag—they’ll hold up their tails. Probably many of you have seen that. It’s an alarm mechanism [below, Wikimedia photo by D. Gordon E. Robertson].

Margaret: Yes. Yes, absolutely.

Brad: And how the scent-based repellents work, is deer’s sense of smell is their primary defense mechanism. If you have a strong odor in your landscape, they are very tentative to go into it because they can’t rely upon that defense mechanism.

Margaret: Right. Are there any other really key strategies that we need to know since, obviously, people can if they wish to join the talk and hear more, they can do that. But any other key strategies that we want to hit on?

Because the parallel fence, the two 4-foot parallel fences, 4 or 5 feet spaced apart, is such a great one. It can be attractive. You can plant in between them, and it can be a nice addition to your landscape. It doesn’t have to look, again, like a prison.

Brad: That’s correct. I have seen some really neat landscapes with this in that it looked fine. It looked very good.

Margaret: Yeah. So is there like one more tip that we want to share?

Brad: I pretty much went at warp speed to give you some of those [laughter].

Margaret: O.K. Because I heard that the professionals are using a chemical repellent that I didn’t know about it.

Brad: Yes. Thank you, Margaret. You are correct.

Margaret: Yeah.

Brad: I didn’t mention it because it’s not available to homeowners. In my research, the best spray-on repellents are what we call Thiram-based. Thiram’s a fungicide and it’s a very effective repellent. And there are some products on the market that homeowners can buy that have Thiram in it, but not at the concentrations needed.

You can have your local landscaper who has a pesticide applicator’s license spray on a product called DeerPro. It’s a restricted-use pesticide so it’s not available to homeowners. But typically if I spray this on in early November on vulnerable plants for winter protection, I will get all-winter protection with one spray-on repellent, if it’s done under ideal conditions.

Margaret: Interesting.

Brad: One last tip, Margaret, quickly. If you or your professional is spraying on repellent during the winter time, it is essential that you pick a day like today. The product has to dry on the leaf surface. And during winter, it takes a long time. If that product is not dry before the temperature dips below freezing, I’ll put it this way: I have carousels of slides of winter injury on conifers and broadleaf rhododendrons strictly due to the repellent froze on the plant and caused tissue damage. So pick a good day.

Margaret: O.K.

Brad: Pick a good day.

Margaret: And keep after the them. Keep after them.

Brad: And be persistent. Absolutely.

Margaret: Well, Brad Roeller, thank you so much for some of these deer tips. And again, I’ll be tuning in, I know, to your lecture for Innisfree Garden on Wednesday, the 23rd. And I’ll talk to you again soon, I hope. Thank you.

Brad: Thank you, Margaret. It’s been fun.

more about deer for gardeners

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the February 21, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).

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