What Plants Smell Like Cat Pee and Why

Several common garden plants produce sulfur-containing volatile compounds that are chemically related to the molecules responsible for cat urine odor, which is why your nose sometimes can’t tell the difference. Boxwood, blackcurrant, valerian, certain viburnum species, and even Sauvignon Blanc grapes all release thiols and related sulfur volatiles that overlap with the specific odorants in cat pee. The connection isn’t just a vague resemblance; in some cases, the exact same molecule is present in both the plant and the urine.

What Makes Cat Urine Smell the Way It Does

To understand why certain plants trigger that unmistakable association, it helps to know which molecules your nose is actually detecting in cat urine. The smell is driven by a group of sulfur-containing compounds, not by ammonia alone as many people assume. Ammonia does build up as urine breaks down, but the sharp, skunky, distinctly feline quality comes from volatile thiols. Research has identified three key odorants: 4-methyl-4-sulfanylpentan-2-one, 3-methyl-3-sulfanylbutan-1-ol, and 3-methyl-3-sulfanylbutyl formate.¹ These are produced when a cat-specific amino acid called felinine, excreted in urine, breaks down over time. The breakdown products are what hit your nose with that pungent, lingering stench.²

The first compound in that list, 4-methyl-4-sulfanylpentan-2-one, deserves special attention. Wine chemists know it as 4-MMP, and it has an extraordinarily low odor threshold: your nose can detect it at concentrations as low as about 3 parts per trillion in liquid.³ This means a plant doesn’t need to produce much of it at all for you to pick up the scent. Even trace amounts floating off a leaf surface on a warm afternoon are enough to trigger that “wait, is there a cat around here?” reaction.

Boxwood, the Most Common Offender

If you’ve ever walked past a boxwood hedge on a hot day and recoiled, you’re not alone. Boxwood (Buxus sempervirens and related species) is probably the plant most frequently accused of smelling like cat urine. The odor comes from a cocktail of sulfur-containing volatiles released by the leaves, especially when they’re warmed by direct sunlight or physically disturbed during pruning. The smell tends to intensify in the heat of summer and diminishes in cooler weather, which is consistent with the broader pattern that temperature is a powerful driver of volatile emissions from plant foliage.⁴

The odor is strongest from English boxwood (Buxus sempervirens ‘Suffruticosa’), the traditional variety used for formal hedging and edging. Korean boxwood (Buxus sinica var. insularis) and some newer hybrid cultivars tend to produce less of that sulfurous punch, so if you love the look of boxwood but hate the smell, switching cultivars can make a real difference. That said, no boxwood variety is completely free of the scent; it’s a matter of degree rather than elimination.

Blackcurrants, Sauvignon Blanc, and the Molecule They Share With Cat Pee

Blackcurrant (Ribes nigrum) is perhaps the most chemically interesting plant on this list because the connection to cat urine isn’t merely a perceived resemblance. The buds and leaves of blackcurrant produce 4-MMP, the same sulfur compound that is one of the primary odorants in cat urine. When you crush a blackcurrant leaf and notice that sharp, musky, catty note underneath the fruity sweetness, you are detecting the exact same molecule a cat uses as a territorial scent marker.

This molecular overlap extends into the wine world. Sauvignon Blanc grapes produce a precursor to 4-MMP, and during fermentation, yeast enzymes cleave it to release the free thiol. At low concentrations, 4-MMP contributes the tropical passionfruit and grapefruit notes that wine drinkers prize in Sauvignon Blanc. At higher concentrations, or in wines from certain growing regions, the same compound pushes toward what tasters describe frankly as “cat pee on a gooseberry bush,” a descriptor that has become almost affectionate in some wine circles. Research has confirmed that the precursor compound, a glutathione conjugate, is present in the grape juice itself before fermentation even begins.³ So the grapes come pre-loaded with cat-pee potential, and the winemaking process determines how much of it ends up in the finished glass.

The fact that “cat pee” is considered a legitimate tasting note in professional wine evaluation tells you something about how pervasive and recognizable this particular sulfur compound is. It’s not a flaw in the wine. It’s a feature, one that happens to share its chemical identity with a component of feline urine.

Other Garden Plants That Trigger the Association

Beyond boxwood and blackcurrant, a handful of other plants are routinely described as smelling like cat urine. The overlap isn’t always caused by the same molecule, but the common thread is sulfur-based volatile chemistry.

Valerian: The roots of Valeriana officinalis produce isovaleric acid and related compounds that give off a sweaty, urinous smell. The above-ground parts are milder, but when the plant is disturbed or the roots are exposed during division, the odor is strong enough to make people check the garden for stray cats. Interestingly, valerian also attracts cats, which can add to the confusion.
Crown imperial: Fritillaria imperialis, the dramatic spring-blooming bulb, is famous for its pungent, foxy, musky smell. The odor has been described variously as skunky, urinous, or like a wet animal, and it comes from sulfur-containing compounds concentrated in the bulb and lower leaves. Gardeners often plant it specifically because the smell is said to repel rodents and deer.
Viburnum tinus: This evergreen shrub produces clusters of small white flowers in winter and early spring that some people find sweet and others find distinctly catty. The perception varies quite a bit between individuals, which may reflect genetic differences in how people detect specific thiol compounds.
Lantana: The leaves of Lantana camara, when crushed, release a complex mix of terpenes and sulfur compounds that many people describe as resembling cat urine. The odor is part of the plant’s defense strategy; the leaves are also toxic to livestock and many other animals.
Privet: Several species of Ligustrum produce flowers with an intense, heavy scent that some people love and others find urinous or fishy. The specific perception seems to be dose-dependent: pleasant at a distance, overwhelming up close.

Individual sensitivity plays a surprisingly large role in who finds these plants offensive and who barely notices. The ability to detect certain thiol compounds varies widely across the human population. Some people have a heightened sensitivity to sulfur volatiles and pick up on cat-urine notes in plants that most others would describe as merely “green” or “earthy.” This is why arguments break out between gardening partners about whether a particular shrub actually smells bad.

Cannabis and the Skunky-Cat Overlap

Cannabis is another plant with sulfur volatiles that overlap with the cat-urine odor profile, though most people describe the smell as “skunky” rather than cat-like. Research identified a new family of volatile sulfur compounds in cannabis that contain a prenyl functional group, with 3-methyl-2-butene-1-thiol pinpointed as the primary source of the skunky aroma.⁵ While this compound is structurally distinct from the thiols in cat urine, it belongs to the same broad chemical family, and the sensory overlap is real. Many people who encounter strong cannabis odor in a closed space will describe it as smelling like cat pee, not just skunk.

The cannabis case is also notable because this sulfur chemistry was only recently characterized. For decades, terpenes like myrcene and limonene were assumed to be the main drivers of cannabis aroma. The sulfur compounds turned out to be present at much lower concentrations but had far greater odor potency, meaning tiny amounts dominated the smell. The same principle applies to plants like blackcurrant and boxwood: the sulfur compounds responsible for the cat-urine note may be minor components of the overall volatile profile, but their extraordinarily low detection thresholds let them overpower everything else your nose is picking up.

Why Plants Produce These Compounds at All

Plants didn’t evolve to annoy gardeners. Sulfur-containing volatile compounds serve real ecological functions, mostly related to defense. When an insect chews on a leaf, the damage triggers a cascade of chemical responses, and sulfur metabolism is a key part of that toolkit. Research on model plants has shown that boosting sulfur-based defense compounds like glucosinolates provides measurable protection against generalist herbivores such as caterpillars.⁶ The pungent thiols that smell like cat urine to us likely taste or smell terrible to the insects and herbivores the plant is trying to deter.

Some of these volatile sulfur compounds also function as signals between plants, or between plants and beneficial insects. When a damaged plant releases sulfur volatiles, neighboring plants can detect them and ramp up their own defenses preemptively. Parasitic wasps and other predators of herbivorous insects are sometimes attracted to these volatile blends, which gives the damaged plant a kind of indirect defense: it calls in reinforcements by smelling bad.

There’s also a simpler explanation for some species. Crown imperial and lantana produce their pungent odors constitutively, meaning they smell without being damaged, and the most likely reason is vertebrate deterrence. A plant that smells like a predator’s urine may discourage grazing animals from approaching, and a plant that smells generally foul is less likely to be browsed. Whether the resemblance to cat urine is coincidental or reflects convergent chemistry around a common “danger” signal for herbivores is an open question in chemical ecology.

When the Smell Gets Stronger

If you’ve noticed that your boxwood or blackcurrant smells worse on some days than others, you’re not imagining it. Volatile organic compound emissions from plants are strongly influenced by temperature, and to a lesser degree by light intensity.⁴ On a hot, still afternoon in July, a boxwood hedge can produce noticeably more volatile sulfur compounds than on a cool, breezy morning in April. The emissions generally peak around midday in summer, which is exactly when you’re most likely to be outside in the garden and downwind.

Humidity can amplify the effect as well. Moist air holds volatile molecules close to the ground rather than dispersing them upward, so a warm, humid day with no wind is the worst-case scenario for cat-pee-smelling plants. Pruning also releases a burst of volatiles because you’re physically breaking open leaf cells, which is why hedge trimming day often produces the strongest complaints. If the timing is flexible, pruning boxwood in cooler weather or in the evening can reduce the intensity of the odor release.

Stressed plants sometimes smell worse, too. Drought stress, root damage, nutrient deficiency, and pest infestation can all shift a plant’s volatile profile toward more sulfur-heavy emissions. A healthy, well-watered boxwood produces some odor; a drought-stressed boxwood produces more. This makes sense from the plant’s perspective since stress signals often overlap with defense signals in plant chemistry.

Managing the Smell in Your Garden

If you already have a cat-pee-smelling plant established in your landscape and don’t want to rip it out, a few strategies can minimize the impact. Positioning matters: placing boxwood or other offenders away from patios, seating areas, and open windows reduces how often you actually encounter the smell. Planting strongly fragrant species nearby, such as lavender, rosemary, or mock orange, can mask or compete with the sulfurous notes.

For boxwood specifically, cultivar selection is probably the most effective long-term approach. If you’re installing new hedging, look for cultivars bred partly for reduced odor. Japanese boxwood varieties (Buxus microphylla) and some of the newer hybrids like ‘Green Gem’ or ‘Green Mountain’ tend to be less offensive than the classic English boxwood, though individual responses still vary.

Watering in the morning rather than at midday can help, because you avoid combining peak temperature with the burst of volatiles released when water hits sun-warmed leaves. And if you prune on a schedule, doing it in cooler parts of the day minimizes the aromatic explosion. None of these strategies eliminate the smell entirely, but they can reduce it to the point where it’s barely noticeable on most days.

The Catnip Twist

There is a curious irony in the relationship between cats and plants. While certain plants smell like cat urine to humans, other plants are famous for driving cats wild through completely different chemistry. Catnip (Nepeta cataria), silver vine (Actinidia polygama), and valerian all trigger the well-known “catnip response” in cats, involving rolling, rubbing, and apparent euphoria. Research has shown that about half a dozen compounds with structures similar to nepetalactone, the active molecule in catnip, can trigger this behavior, along with the structurally distinct molecules actinidine and dihydroactinidiolide.⁷

Valerian lands on both lists: it smells like cat pee to many humans, and it attracts cats through a separate set of active compounds. This dual identity creates a feedback loop that some gardeners find maddening. You plant valerian for its medicinal or ornamental value, it smells vaguely of cat urine, and then actual cats show up and roll around in it, leaving behind real cat urine. The plant didn’t evolve for this purpose, but the chemical overlap between what attracts cats and what smells urinous to us creates a perfect storm of feline attention.

The compounds that attract cats (nepetalactone and its relatives) are terpenes, not sulfur compounds, so they operate through an entirely different chemical pathway than the thiols responsible for the cat-urine smell. The connection is more about convergence than shared chemistry. Plants that make one kind of pungent volatile happen, for unrelated evolutionary reasons, to sometimes also make the other. Your garden is a chemistry lab, and the occasional overlap between “smells like cat pee” and “attracts actual cats” is one of its less charming outputs.