Growing up on our family farm, I quickly learned that horses have surprisingly strong opinions about the plants around them. Some evenings, I’d watch our mare Daisy deliberately avoid certain areas of the fence line where particular herbs grew wild.
Most horse owners focus on which plants are toxic, but fewer realize that certain perfectly safe plants emit scents that horses simply can’t stand. This knowledge can be incredibly useful, whether you’re trying to keep horses away from garden borders or wondering why they avoid certain parts of your property.
I’ve compiled this list of plants that make horses wrinkle their noses and back away—plus some friendlier alternatives they actually enjoy.
1. Peppermint
The strong menthol compounds in peppermint overwhelm a horse’s sensitive nose. While humans find the scent refreshing, horses often back away when encountering concentrated mint aromas in the garden.
Interestingly, small amounts of dried mint in treats can be appealing to some horses, but the intense aroma of living plants growing nearby is a different story. Our neighbor’s quarter horse would consistently avoid grazing near the wild mint patch at the edge of his pasture.
The intensity matters—a few plants might be tolerable, but a dense mint border creates an effective natural barrier that most horses won’t cross.
2. Lavender
Those beautiful purple spikes might smell heavenly to us, but lavender’s intense fragrance contains terpenes that horses find overwhelming. The concentrated essential oils can irritate their sensitive olfactory systems, causing them to steer clear.
My aunt’s dressage horse would actually snort and toss his head when ridden past her lavender garden. The plant’s silvery foliage and drought resistance make it perfect for garden borders that you want horses to avoid.
French lavender varieties seem particularly effective as deterrents, with their stronger camphor notes that horses find especially unpleasant.
3. Marigolds
Ever notice how pungent marigolds smell when you brush against them? That distinctive, somewhat sulfurous scent comes from thiophenes—compounds horses find particularly offensive. Their bright orange and yellow blooms might look cheerful to us, but horses want nothing to do with them.
We planted a row of marigolds along our vegetable garden fence, and our curious gelding who previously leaned over to munch our tomatoes suddenly lost all interest in that area. The stronger-scented varieties like ‘Tagetes erecta’ work best for this purpose.
As a bonus, marigolds also repel many garden pests while creating an equine-proof barrier.
4. Eucalyptus
The powerful mentholated aroma of eucalyptus contains cineole, a compound that horses find particularly overwhelming. Even a single potted eucalyptus plant can create a strong enough scent barrier to discourage horses from approaching.
When we added a small eucalyptus tree near our paddock fence, our previously fence-rubbing mare stopped that habit entirely. The silvery-blue foliage adds beautiful contrast to gardens while serving as an effective equine deterrent.
Dwarf varieties like Eucalyptus gunnii work well in smaller spaces and still produce that distinctive scent horses avoid.
5. Wormwood
Known botanically as Artemisia absinthium, wormwood contains thujone—a bitter compound with a scent horses absolutely detest. Its silvery-gray foliage might look delicate, but it packs a powerful olfactory punch that keeps horses at bay.
During a particularly dry summer, our neighbor’s horses broke through a weak fence section but completely avoided the area where wormwood grew wild. The plant’s drought tolerance makes it perfect for dry garden borders you want to protect.
Just be careful about placement, as wormwood can inhibit the growth of nearby plants through allelopathy.
6. Citronella
“My horses won’t even approach the fence where I planted citronella,” a local riding instructor told me last summer. The lemony, sharp scent that repels mosquitoes works equally well on horses, who find the concentrated oils irritating to their sensitive noses.
Citronella grass (Cymbopogon nardus) grows in attractive clumps that can reach three feet tall, creating both a visual and olfactory barrier. The plant releases more oils when brushed against or on hot days, making it especially effective during summer months.
As an added benefit, you’ll enjoy fewer biting insects near your outdoor seating areas.
7. Russian Sage
Russian sage emits a pungent, almost medicinal aroma from its silver-gray foliage that horses find deeply unpleasant. The plant’s tall purple flower spikes create a beautiful garden feature while establishing a boundary horses won’t cross.
Last fall, I watched my friend’s curious draft horse stretch his neck toward every plant along the fence line except for the Russian sage—he gave that a wide berth. The drought-tolerant perennial thrives in poor soil conditions where other plants struggle.
For maximum effectiveness, plant several in a row to create a concentrated scent barrier that maintains its deterrent properties even in windy conditions.
8. Tansy
Tansy’s bright yellow button flowers might look cheerful, but they contain thujone and camphor compounds that create a scent horses actively avoid. The strong, somewhat bitter aroma lingers even after rain, making tansy an effective year-round deterrent.
When we added tansy to our herb garden border, our neighbor’s horse stopped reaching over to grab mouthfuls of our other plants. The dense foliage grows quickly, creating an effective barrier within a single season.
Just handle with gloves—the oils that repel horses can also irritate sensitive human skin when crushed.
9. Santolina (Cotton Lavender)
Don’t let the name fool you—cotton lavender isn’t related to true lavender, but its effect on horses is similar. The silvery foliage emits a strong, camphor-like aroma that horses find particularly offensive, causing them to avoid areas where it grows.
Our farm’s perimeter garden included santolina, and even our most determined fence-leaning mare wouldn’t approach that section. The drought-tolerant Mediterranean native thrives in poor soil and hot conditions, making it perfect for dry garden borders.
Its compact growth habit and yellow button flowers add year-round interest while creating an effective equine barrier.
10. Rue
Medieval gardeners knew rue’s bitter scent repelled pests—including large browsing animals like horses. The blue-green foliage contains powerful furocoumarins that create an aroma horses find deeply unpleasant and will actively avoid.
When my sister planted rue along her garden fence, her neighbor’s persistent fence-reaching horse suddenly lost all interest in that boundary. The plant’s interesting foliage and yellow flowers make it ornamentally valuable beyond its horse-deterring properties.
Handle with care though—the same compounds that repel horses can cause skin irritation in humans, especially in sunny conditions.
11. Rosemary
While humans love rosemary’s pine-like fragrance, horses find its concentrated essential oils overwhelming and irritating. The woody perennial’s strong scent intensifies in hot weather, creating an effective barrier that horses typically won’t cross.
My aunt’s garden featured a rosemary hedge along the pasture fence—her horses would graze right up to it but never attempt to reach over or through it. The plant’s drought tolerance and year-round structure make it perfect for permanent garden boundaries.
Upright varieties like ‘Tuscan Blue’ create the most effective barriers, with their strong vertical growth and concentrated oils.
12. Yarrow
This one contains thujone—the same compound found in wormwood that horses strongly dislike. Its feathery foliage releases a sharp, medicinal scent when brushed against that horses find particularly offensive.
After adding yarrow to our garden border, we noticed our neighbor’s curious gelding would approach every section of the fence except where the yarrow grew. The plant’s drought tolerance and colorful summer flowers make it both practical and ornamental.
For maximum effectiveness, choose aromatic varieties like Achillea millefolium rather than the newer, less scented cultivars bred primarily for flower color.
13. Lemon Balm
Lemon balm’s citrusy scent comes from citronellal compounds that horses find irritating to their sensitive noses. Unlike some milder herbs, lemon balm’s concentrated oils create an aroma strong enough to deter even the most curious equines.
My cousin’s garden borders her horse pasture, and she swears by lemon balm as a natural boundary her horses won’t cross. The vigorous perennial spreads readily, quickly establishing a dense, aromatic barrier that intensifies when brushed against or after rain.
Consider planting it in containers if you’re worried about its spreading habit—the scent deterrent works just as effectively.
14. Timothy Grass
Unlike our previous entries, timothy grass produces a sweet, hay-like scent that horses find irresistibly appealing. The grass grows in attractive clumps that add texture to garden borders while creating a horse-friendly boundary.
We planted timothy along one section of our garden where we actually wanted the horses to approach. They’d visit regularly but rarely overgraze it, creating a perfect harmony between garden and pasture.
The grass establishes quickly from seed and tolerates moderate foot traffic, making it ideal for transitional areas between formal gardens and horse-accessible spaces.
15. Calendula
Bright orange calendula flowers bring cheerful color to garden borders while producing a mild, pleasant scent that doesn’t offend equine visitors. Unlike marigolds with their sulfurous aroma, calendula’s gentle fragrance is actually attractive to many horses.
When I planted calendulas along our riding arena border, our horses would often pause to investigate them without trying to eat them. The edible flowers are even safe if occasionally nibbled, though most horses seem content just to enjoy their sunny presence.
Their prolific self-seeding habit ensures they return year after year with minimal effort.
16. Chamomile
Chamomile’s apple-like fragrance creates a soothing atmosphere that horses generally find pleasant rather than offensive. The delicate white flowers with yellow centers add charming texture to garden borders while remaining compatible with equine neighbors.
Roman chamomile forms a lovely low-growing ground cover that can handle some foot traffic, perfect for garden edges where horses might occasionally step. When our mare Penny would reach over the garden fence, she’d gently investigate the chamomile without trying to devour it.
The plant’s stress-reducing properties seem to work on horses as well as humans—we’ve noticed our horses appear calmer near the chamomile patch.
17. Sunflowers
Majestic sunflowers create dramatic garden backdrops without producing scents that bother horses. Their mild, slightly nutty fragrance is generally neutral to equine noses, allowing them to coexist peacefully alongside your four-legged friends.
Last summer, we planted a sunflower border between our vegetable garden and the horse paddock. The horses seemed fascinated by the tall yellow blooms, often standing nearby to observe them without trying to eat them.
Choose perennial varieties like Helianthus maximiliani for long-term borders, or plant annual types for seasonal impact—both work equally well in horse-adjacent gardens.
18. Nasturtiums
Trailing nasturtiums create vibrant garden borders with their round leaves and bright flowers in shades of orange, yellow and red. Their mild, peppery scent is interesting to horses but not offensive—most equines will investigate without overindulging.
“My gelding loves to watch the nasturtiums sway in the breeze,” my riding instructor mentioned last spring. The edible flowers and leaves are actually safe for occasional equine sampling, though most horses seem content just to appreciate them visually.
Their sprawling growth habit quickly fills empty spaces along fence lines, creating colorful boundaries that won’t send your horses running in the opposite direction.