Newly planted trees, defined as those installed within the last year, require careful winter care. The common assumption that trees need zero attention during the dormant season is incorrect. Proper moisture management during the colder months is fundamental for the tree’s survival and the successful establishment of its root system. Ignoring winter hydration can lead to significant damage that only becomes visible when spring growth fails to emerge.
Why Newly Planted Trees Need Water During Dormancy
While the above-ground canopy of a tree may be dormant, its root system remains physiologically active and continues to lose moisture to the surrounding soil. Newly planted trees are especially susceptible to drying out because their roots are confined to the original planting hole and have not yet spread to access deeper water reserves. This moisture loss, known as desiccation, is often intensified by dry winter winds and strong sun exposure. Evergreens, which retain their foliage, are particularly affected by desiccation.
The root systems of most tree species continue to grow slowly throughout the winter months, provided the soil temperature remains above freezing. Root growth is optimal when soil temperatures are between 40°F and 65°F, and some growth still occurs slightly below 40°F. Supplying supplemental water prevents fine roots from drying out, supporting establishment and helping the tree build energy reserves for spring growth. Moist soil also holds heat better than dry soil, insulating the roots from extreme cold and preventing injury.
The Baseline Winter Watering Schedule
For newly planted trees, the standard recommendation is to provide a deep soaking every two to four weeks during the winter, assuming there has been no significant natural precipitation. This frequency is a starting point; the ultimate decision to water must be based on the condition of the soil, not strictly on the calendar. Before applying water, a soil check is necessary to determine if the top four to six inches of the ground are dry.
The absolute rule for winter watering is that it must only occur when the air temperature is above 40°F and the ground is not frozen solid. Watering into frozen soil is ineffective because the water cannot penetrate the root zone and will simply run off or create dangerous surface ice. To check for frozen ground, attempt to drive a screwdriver or trowel six to nine inches into the soil. If the ground resists penetration, it is likely too frozen to absorb water.
Watering is best done during the late morning or midday hours. This timing allows the water to soak into the root zone while the sun is out and provides time for any excess surface moisture to dissipate before nightfall. Applying water during the warmest part of the day reduces the risk of the soil surface freezing immediately after application.
Factors That Adjust Watering Frequency
Several environmental and biological factors necessitate adjustments to the standard two-to-four-week watering interval. The type of soil present significantly influences how long moisture is retained. Trees planted in sandy soil drain quickly and may require more frequent watering. Conversely, clay-heavy soils hold moisture longer, meaning the interval can be safely extended.
The tree species is a major consideration because evergreens lose moisture year-round through their needles. Due to this constant transpiration, evergreens are more susceptible to desiccation and often require more frequent supplemental watering than deciduous trees. Local climate conditions, such as prolonged periods of strong winter winds or intense sun exposure, also increase the rate of moisture loss from the tree and the soil. If the region experiences an extended dry spell without snow cover or rain, supplemental watering becomes necessary, regardless of the typical schedule.
Best Practices for Applying Winter Water
The goal of winter watering is a slow, deep application that saturates the root zone without causing runoff or soil saturation. A newly planted tree typically requires between two and five gallons of water for every inch of its trunk diameter, measured six inches above the soil line. For example, a tree with a two-inch diameter trunk may need between four and ten gallons per application.
The water should be applied slowly using a soaker hose, drip system, or a slow trickle from a hose, allowing the moisture to penetrate to a depth of at least 12 inches. Concentrating the water over the root ball and out to the drip line is the most effective approach. Avoid applying water directly against the trunk, as consistently wet bark can invite disease.