Boxwood shrubs are a favorite for formal landscaping, but their dense, evergreen foliage often comes with a distinct and unpleasant musky odor, frequently described as skunky or similar to animal urine. This persistent smell is a common issue for homeowners, especially when the plants are located near windows, patios, or entryways. Understanding the cause and implementing specific horticultural and cleaning practices can effectively manage this odor. This guide provides practical steps to eliminate the boxwood smell, from long-term plant management to immediate neutralization techniques.
Understanding Why Boxwoods Smell
The characteristic pungent odor originates from chemical compounds naturally produced by the plant, primarily in the leaves and stems. While some research points to sulfur-containing compounds like mercaptans, the “fishy” or “ammonia-like” scent is often associated with trimethylamine (TMA). TMA is a degradation product of high-nitrogen organic matter, including choline and betaine found in plants, and it is released as the plant naturally processes these compounds.
The smell becomes most noticeable when the air is stagnant, humid, or when the shrubs are exposed to direct, intense sunlight. High heat and moisture can accelerate the release of these volatile organic compounds from the plant’s surface. Furthermore, the dense structure of the shrub traps fallen leaves and debris inside, which then decompose and intensify the ammonia-like odor. Buxus sempervirens, or English boxwood, is the species most commonly linked to the strongest odor.
Cultural and Pruning Strategies
The most effective long-term strategy for reducing boxwood odor involves improving the plant’s environment to promote better air circulation. Boxwoods that are continuously sheared into dense, solid shapes create a thick outer shell, which prevents light and air from reaching the inner foliage. This stagnant, damp interior is where debris accumulates and the odor-producing compounds are most concentrated.
Instead of only shearing the exterior, selectively thin the shrub once a year, preferably in late winter or early spring before new growth begins. Use hand pruners to reach into the canopy and remove individual branches back to a larger branch or the main stem. This “thinning” creates small pockets or holes within the shrub, allowing sunlight and air to penetrate the center. This technique helps the inner leaves dry out faster, reduces the accumulation of damp, decaying debris, and minimizes the conditions that intensify the smell.
Beyond pruning, managing the soil environment is also important because overly wet soil can exacerbate the issue. Ensure the boxwood is planted in well-draining soil and avoid overwatering, as poor drainage causes stress and creates a humid microclimate around the base of the plant. Regularly rake or remove any fallen leaves and debris from underneath the shrub’s canopy to prevent them from decomposing and contributing to the smell. Keeping the soil surface clean and dry is an important step in managing the overall odor.
Immediate Odor Neutralization Methods
For a quick, short-term fix, especially when the shrub is near a high-traffic area, focus on neutralizing the odor on surrounding hard surfaces. The pungent smell can adhere to nearby walkways, patios, and walls, where wind-blown debris or chemical residue has settled. Start by thoroughly hosing down all hard surfaces around the boxwood to wash away any odor-holding particulates.
A simple, effective DIY cleaning solution is diluted white vinegar, which works to neutralize alkaline odors like ammonia. Mix a solution of one part white vinegar to two parts water and spray it onto the adjacent patio or brickwork. Allow the solution to sit for 20 minutes before rinsing it thoroughly with clean water, making sure to avoid spraying the solution directly onto the plant’s foliage.
Baking soda can also be used as a deodorizer on non-porous surfaces by mixing it into a paste with water and scrubbing it into the affected area. For a commercial approach, enzyme-based cleaners designed for pet odor are highly effective because they contain specialized bacteria that break down the organic molecules responsible for the ammonia-like scent. Apply these enzyme products to the ground or patio surface around the boxwood, following the manufacturer’s instructions for dilution and contact time.
Selecting Alternatives for Future Planting
For those considering replacing a particularly offensive boxwood, several low-odor cultivars and alternative species offer a similar dense, evergreen aesthetic. When choosing a boxwood, look for varieties derived from Buxus microphylla (Littleleaf Boxwood) or its hybrids, as they are known to have significantly less odor than the common Buxus sempervirens (English Boxwood).
Specific low-odor cultivars offer the classic boxwood look without the strong scent:
- ‘Green Mountain’
- ‘Green Velvet’
- ‘Wintergreen’
- ‘Sprinter’ (noted for its fast growth and lack of odor)
If you prefer to avoid the genus entirely, excellent evergreen alternatives can provide the same formal structure. Japanese Holly (Ilex crenata) varieties, such as ‘Helleri’ or ‘Compacta,’ have small, dark leaves that closely mimic the texture of boxwood and respond well to shearing. Inkberry Holly (Ilex glabra) is another native option with a dense, rounded shape and glossy leaves. Yew shrubs (Taxus spp.) are also a suitable choice, as they are highly tolerant of heavy pruning and can be shaped into formal hedges or topiary forms.