For those of us who garden in areas with high numbers of deer, it’s easy to get discouraged. A new approach seems to be in order. After studying which plants have survived in my highly deer-pressured gardens, I decided that this year I will add only plants that are either smelly (to deer at least), fuzzy, or poisonous (preferably to deer only). Also allowed: grasses, in which deer have so far expressed no interest.
There are the usual suspects — fuzzy lamb’s ears and rose campion, toxic milkweed, and plants with needle-y foliage and milky sap like blue star (Amsonia hubrichtii), all of which are pretty deer-resistant. Were there other plants that fit my new criteria? I was curious about plants that are toxic, so I looked into that category first.
I have to admit that the toxicity element makes me nervous, but through some research, I learned that most plants have some level of toxicity — an adaptation that aids survival. If you doubt this, take a look at the long list of plants identified in Poisonous and Injurious Plants of the United States: A Bibliography and in Safe and Poisonous Garden Plants/ Toxic Plants/Univ.California . Many plants in our gardens can be found on that list, including rhododendron, mountain laurel, elderberry, pieris, elephant ears, oleander, daffodils, autumn crocus, jack in the pulpit, lily of the valley, and the list goes on and on. You’ll probably want to be familiar with the most toxic of the plants you or your family might encounter, and for that, I highly recommend The Socrates Project: Poisonous Plants in Virginia.
One garden plant well known for its toxicity is common milkweed (Asclepius syriaca), a delightful native, which almost never gets even a nibble in my yard. I was surprised to discover that milkweed has only a medium level of toxicity and is often browsed by both deer and rabbits, though it can be fatal to horses. Rabbits apparently only try a few bites of the stems late in the growing season, when the toxicity wanes. Deer are ruminants, which means they have specialized rumen microbes which degrade or inactivate many toxic substances in plants. Now I understand how deer can feast on cherry laurels despite the laurels’ high toxicity. To learn more about this and some fascinating animal adaptations to toxic plants, check out Cornell CALS/Plants Poisonous to Livestock and Other Animals.
I had high hopes for mountain laurel after reading about its high level of toxicity to animals and humans. Amazingly, “if honey bees feed heavily on these plants, they are known to produce ‘mad honey’ that can be toxic for human consumption.” NC State.edu/Kalmia latifolia. But as was the case with milkweed, deer can manage to eat mountain laurel, thanks to their specialized rumen microbes. In fact, many poisonous plants are not particularly toxic to deer. Why deer avoid some toxic plants but not others remains a mystery, one that scientists are still exploring.
My criteria was beginning to seem awfully limiting, but new frontiers opened up as I examined the aromatic herb category a bit more closely. In the past, I’ve sowed a few culinary herbs into my cutting garden, and some were quite pretty. Dill, for example, has beautiful flowery seed-heads, but has never been munched by deer, probably because of its odor. Why not expand its territory beyond the one little patch and let it take the role of “ornamental” in my beds? Surely there were other herbs that were attractive to humans — but not deer! A bit of research confirmed which common herbs were smelly enough to repel deer, and for that element, take a look at the list below.
Blandy Experimental Farm/Arboretum/Planting Resources/Deer Resistant or Not
Smelly but Pretty Herbs
Some herbs are strong candidates for the ornamental garden, and the first one on the list above has long been part of my ornamental beds; I even wrote an article about it: Anise Hyssop/The Garden Shed/2021. A public garden in my former home town, Salt Lake City, is employing dill as an ornamental; check out the photo below. Most herbs came from the Mediterranean region and traveled to North America with the earliest settlers, so they’re not native. But since many are easily grown from seed, gardeners can quickly and inexpensively populate their ornamental gardens with attractive plants that deer will in all likelihood avoid — and with no worries about accidentally introducing an invasive. Just remember that if you let culinary herbs flower, they won’t be as flavorful. For the basics on growing herbs, check out How to Grow, Harvest and Preserve Culinary Herbs/The Garden Shed as well as Herbs That Taste and Smell Like Lemon/The Garden Shed, which suggest a number of possibilities for ornamental herb gardening.
Dill (Anethum graveolens): I should not have been surprised that dill’s specific epithet (species name) is graveolens, which means strong-smelling. Deer tend to avoid strong-smelling plants, and research soon revealed that more than one of the plants that fit my new criteria share that species name.
Sage (Salvia officianalis): Culinary sage has somewhat fuzzy, slightly gray leaves, plus the smelly factor, all of which probably make it less popular with deer. If you keep a culinary sage plant going long enough, it will flower. My old sage has overwintered in a pot for many years on the deck. When the blue flowers appeared, it was a wonderful shock. Worth a try out in the garden, right? No less an authority than Missouri Botanical Garden has commented on sage’s “excellent ornamental qualities.”
Mint (Mentha suaveolens): Due to its reputation for acting like an invasive, most of us keep mint confined in a pot. I have a “passalong” mint that produces white blooms in summer and which appears to fall in the category of apple mint or perhaps pineapple mint. My mother-in-law referred to it as “Winterthur mint.” Being a fairly aggressive spreader, it makes a reasonably attractive hillside soil-holder.
But there are the newly-popular mountain mints (Pycnanthemum) which seem to have it all: they’re native, they’re beloved by pollinators, deer avoid them, and they make a lovely addition to the garden. Their secret ingredient is pulegone, which gives their leaves a highly aromatic “minty but medicinal” smell, repelling both deer and mosquitos.
There are four species of mountain mint that are native to our area:
- Hoary Mountain Mint (Pycnanthemum incanum)
- Short Toothed or Clustered Mountain Mint (Pycnanthemum muticum)
- Narrow Leaf Mountain Mint (Pycnanthemum tenuifolium)
- Virginia Mountain Mint (Pycnanthemum virginianum)
Mountain mints are good candidates for the back-of-the-border position in sunny beds. To learn more about mountain mints, read Mountain Mint — Truly a Gardener’s Mint/Rutgers.edu.
When I read that pulegone is also present in pennyroyal, I did some research and learned that the essential oil from the pennyroyal plant is highly toxic, causing liver damage and death to humans and dogs when ingested even in small amounts. Of course, the essential oil will be much more concentrated than the pulegone in the plant itself, but I nevertheless decided against adding pennyroyal to the garden.
Rosemary (Salvia rosmarinus, formerly known as Rosemarinus officinallis): There are several varieties of rosemary, some upright, some spreading; the latter look great cascading over a wall. Rosemary needs well-drained soil and full sun. It tolerates drought, but not wet soil, which can lead to root rot. In fact, a winter in wet soil can kill this plant. My research suggests that my new little rosemary plant will do best at the top of a slope situated among some rocks.
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Mexican tarragon or mint marigold (Tagetes lucida): I am experimenting with this plant, a native of Mexico and Central America, where it is a perennial. It is recommended as a heat-and drought-tolerant substitute for true tarragon, which is difficult to grow in the South. Its tall habit is what I find appealing. Note that it has low severity toxicity. It needs full sun and well-drained soil. It is grown as an annual in zones colder than Zone 8.
Rue (Ruta graveolens) — which has glorious blueish leaves — found its way into my garden when I picked it up in the “Herbs” section at the nursery. I didn’t realize it at the time, but this is definitely NOT a culinary herb. Historically it was used as a medicinal herb, but it is quite toxic, causing contact dermatitis (wear gloves), “stomach pain, vomiting, exhaustion, confusion, and convulsions and can be fatal,” according to NC State Extension. I only recently discovered this fact, so I feel fortunate that none of our dogs or children ever tried a bite. Could the toxins give off a repellent odor? In any event, rue may not be for you if your garden is frequented by children or pets.
Besides being deer-resistant, rue has other admirable traits — it is drought and heat tolerant and supports several species of swallowtail butterflies! I’m not a fan of its yellow flowers, but they’re no doubt attractive to many gardeners. Some research suggests that this plant or a similar species may have various medical applications and has potential as a pest repellent A recent article reports that extracts from Ruta graveolens “showed good antibacterial and antifungal properties.”
Borage (Borago officinalis): Borage has become one of my favorite plants, mostly due to its ethereal blue flowers. But it has other desirable traits: it is a self-sowing annual and likes sunny, dry areas. Deer have not yet bothered it in my yard, perhaps due to its hairy leaves. Despite its low-severity toxicity, its leaves — when young — can be added to salads for a cucumber flavor. The flowers are attractive to pollinators. Borage has an entry in the Digital Atlas of the Virginia Flora because it escaped cultivation on Wildcat Mountain in Fauquier County in the 1960’s and has persisted there ever since.
Chives (Allium schoenoprasum) and other onions
Most onions are avoided by deer, so members of this family are naturals for the deer-free ornamental garden. Chives will form beautiful lavender-blue flowers in May or June, but my new favorite is garlic chives (Allium tuberosum), which has tall stems and beautiful white flowers later in the season, July or August. This plant can handle a fair amount of shade. Not a single flower has yet been eaten by a deer — and you certainly can’t say that about daylilies! Garlic chives is known for its spreading and self-seeding tendencies; it has self-seeded in my garden, and it fits nicely everywhere!
Ornamental onions are also on the list. I for one am eager to add them to my garden. Read more about their gorgeous flowers and recommended varieties in Master Gardener Favorites and Allium/The Garden Shed.
It seems I’ve only scratched the surface of the potential for herbs in the ornamental garden. If you’re interested in growing lavender, be sure to read Growing Lavender in Central Virginia/The Garden Shed. Both thyme and oregano seem to have the potential to be ornamentals, so I’m planning to experiment with them next. And then there’s the artistic challenge — how best to combine these “ornamental herbs” with other plants in the garden. This little journey has banished my discouragement, and I hope that you, too, will be invigorated by exploring new ways with herbs.
SOURCES
Featured Photo: Anise hyssop and lamb’s ears in the author’s garden. Photo: Cathy Caldwell
“Mountain Mints,” Piedmont Native Plants: A Guide for Landscapes & Gardens (Plant Northern Piedmont Natives Partnership) (Note: this guide can be purchased or downloaded, see https://www.plantvirginianatives.org/native-plants-for-northern-piedmont
“Herb Culture and Use,” Va. Coop. Ext.
“Mountain Laurel — The Living Legacy,” The Deer-Forest Blog (Penn State Ext. 2015)
Deer Resistant Plants/NC State Extension
“Anethum graveolens,” NC State Extension
“Mountain Mint,” Clemson Extension
“Salvia officinalis,” Missouri Botanical Garden PlantFinder
“Salvia rosmarinus,” NC State Extension
“Rue,” Roots of Medicine/Univ. of Iowa College of Pharmacy
ResearchGate/Natural Products Chemistry & Research
“Ten Ornamental Herbs,” Fine Gardening
The Socrates Project: Poisonous Plants in Virginia (University of Virginia 2d ed. 2020) (a project of Virginia Master Naturalists in collaboration with UVA School of Medicine Department of Toxicology and the University of Virginia Health’s Blue Ridge Poison Center)
“Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants,” Pediatr. 98: 944-947 (Bakerink, J. A. et al. 1996)
“Pennyroyal”. GMU.edu
“Borago officinalis,” North Carolina State Extension
“Tagetes lucida,” North Carolina State Extension
Growing chives in home gardens,” University of Minnesota Extension
“Allium tuberosum,” Missouri Botanical Garden.org/PlantFinder
“Poisonous and Injurious Plants of the United States: A Bibliography” digitalcommons.humboldt.edu
(James P. Smith Jr, Humboldt State University)
“Not Easy Being Mead’s: Comparative Herbivory on Three Milkweeds, Including Threatened Mead’s Milkweed (Asclepias meadii),and Seedling Ecology of Mead’s Milkweed,” (Thesis by Steven Michael Roels, University of Kansas 2011), kuscholarworks.ku.edu
“Amsonia hubrichtii,” NC State Extension