Boxwood (Buxus species) is a widely used evergreen shrub, known for its dense foliage and suitability for hedges and topiary. The plant emits a noticeable and distinctive odor, particularly under specific environmental conditions. This scent is highly recognizable, but reactions to it vary widely, ranging from enjoyment to strong dislike. The aroma’s intensity increases when the plant’s volatile compounds are easily released into the air.
What Boxwood Odor Smells Like
The scent released by boxwood is frequently debated, as the perception of its aroma differs significantly among individuals. Those who find the smell unpleasant often describe it as having a strong resemblance to cat urine or a musky, ammoniacal odor. This pungent quality is particularly associated with the popular English boxwood, Buxus sempervirens.
Other descriptions include resinous, musky, or a strong, acrid green scent. The odor can also be characterized as stale or damp, especially when the shrubs are planted in shaded or enclosed areas. The subjective nature of the aroma explains why the shrub remains a landscape staple despite its unusual reputation.
The Chemical Source of the Scent
The distinctive boxwood odor is caused by the release of specific nitrogen-containing organic compounds that become volatile in warm conditions. The primary molecule linked to the unpleasant, urine-like scent is trimethylamine (TMA). TMA is a simple tertiary amine, which is also responsible for the “fishy” odor associated with decomposing fish.
Boxwood shrubs naturally contain various alkaloids, which are nitrogen-rich compounds that degrade and release TMA in the presence of heat and moisture. The scent is amplified on sunny, hot days when the sun warms the leaves and volatizes the plant’s oils. High humidity or recent rain also contributes to the increased noticeability of the odor.
Managing Boxwood Scent in the Garden
For those who find the boxwood scent undesirable, the most effective management strategy involves thoughtful placement and cultivar selection. Homeowners should avoid planting the more fragrant English boxwood cultivars near high-traffic areas, such as patios, decks, or entryways. Placing these shrubs further out in the landscape helps to disperse the odor before it reaches seating areas.
Selecting a less fragrant boxwood variety can also mitigate the issue, as odor intensity varies by species and cultivar. Certain Asian boxwoods, such as Buxus microphylla varieties, have a significantly milder or non-existent scent compared to the English type. If the scent is a major concern, replacing the shrubs with a different evergreen, such as Japanese holly (Ilex crenata), provides a similar aesthetic without the associated smell.