Boxwoods (Buxus spp.) are popular evergreen shrubs prized for their dense foliage and versatility in the landscape. Because these plants are relatively shallow-rooted, they are highly susceptible to fluctuations in soil moisture. Proper watering practices are the single most important factor for maintaining the health and appearance of boxwoods, preventing stress that can lead to disease.
Watering Newly Planted Boxwoods
The first one to two years after planting are the establishment phase where a boxwood’s watering needs are highest. During this period, the goal is to keep the root ball consistently moist, but never saturated, to encourage new root growth into the surrounding soil. Immediately after planting, a deep soaking is necessary to settle the soil and eliminate air pockets around the roots.
For the first few weeks, a newly planted boxwood may need water every few days, especially during hot, dry weather. Aim to provide approximately one inch of water per week, including any natural rainfall, for the first 18 to 24 months.
When watering, apply the water slowly and deeply using a soaker hose or drip irrigation. Deep, infrequent watering promotes roots to grow outward and downward, creating a more robust and drought-tolerant plant. Surface sprinkling should be avoided as it encourages shallow root development and moisture loss through evaporation.
Watering Established Boxwoods
Once a boxwood is considered established, typically after two full growing seasons, its watering routine shifts. Mature boxwoods possess a greater degree of drought tolerance, but they still require supplemental water during dry conditions. The standard rule of thumb is to provide a deep watering session once a week during periods of active growth without rain.
A deep watering means delivering enough water to wet the soil to a depth of six to eight inches. Allowing the upper layer of soil to dry out between watering sessions encourages deeper root growth. Before applying water, check the soil moisture by inserting a finger two inches into the ground near the base of the shrub.
If the soil feels dry and crumbly at that depth, it is time to water. If the soil still feels cool and damp, delay watering for a few days to prevent root rot.
Adjusting Watering Based on Season and Environment
During the peak heat of summer, boxwoods will lose moisture more rapidly through transpiration. Watering frequency may need to increase to twice a week under these conditions to compensate for the rapid moisture loss.
As boxwoods enter a slower growth phase in the fall and winter, their water requirements decrease significantly. From late autumn through early spring, established shrubs rarely need supplemental water unless there is a prolonged dry spell. However, a deep watering before the ground freezes in late fall is beneficial, helping to prevent winter desiccation.
Soil type plays a significant role in water retention. Sandy soils drain quickly and require more frequent, smaller applications of water, while heavy clay soils hold moisture longer and need less frequent watering.
Boxwoods grown in containers are particularly vulnerable to drying out. They will require daily checks, often needing water every day during hot weather because the soil volume is limited.
Recognizing Signs of Water Stress
Observing the foliage helps determine if the current watering strategy is effective. Underwatering initially presents as a dulling of the leaf color and a lack of luster in the foliage. The leaves will turn yellow, the tips may brown, and the leaves will feel brittle or crisp to the touch.
Overwatering can produce similar symptoms to drought stress. An overwatered plant may exhibit yellowing leaves, but the soil will be saturated, and the leaves may appear dark or black, often drooping but feeling soft instead of brittle. The most severe consequence is root rot, caused by a lack of oxygen in waterlogged soil, leading to mushy roots and plant decline.
Always check the soil moisture first. If the plant shows signs of stress and the soil is wet, the problem is likely overwatering. The wilting caused by root rot is a sign that the damaged roots can no longer take up water, even though the soil is saturated.