The change in seasons naturally brings questions about how to care for plants, particularly concerning their water intake. Plants still require hydration to sustain physiological processes, even when temperatures drop and days grow shorter. The frequency and volume of watering must change dramatically from the summer routine. The primary challenge is adjusting to the slower pace of winter growth while avoiding overwatering, which can be more destructive than underwatering during the cold months.
How Winter Conditions Affect Plant Water Needs
Plant metabolism shifts significantly in response to the reduced light and cooler temperatures of winter. Shorter days mean less available natural light, which directly lowers the rate of photosynthesis. This slows growth considerably, entering a period often referred to as quiescence. This slowed growth rate means the plant consumes much less water than it does during the active summer season.
Lower ambient temperatures also contribute to reduced water usage. Evaporation from the soil surface is naturally slower in a cooler setting, meaning the potting medium or garden bed remains moist longer. Additionally, the rate of transpiration—the process of water movement through a plant and its evaporation from aerial parts—decreases. This combination of factors establishes the basis for reducing the watering schedule, as maintaining a summer routine would quickly lead to waterlogged soil.
Adjusting Watering for Indoor Plants
Caring for houseplants in winter presents a unique paradox. While low light levels signal the plant to reduce water intake, central heating systems drastically dry the indoor air. This dry air can increase water loss from the leaves and soil surface through evapotranspiration, potentially causing plants to dry out faster than expected despite slowed growth. Therefore, watering frequency must be based on the specific moisture level of the soil, not a fixed schedule.
The most reliable way to gauge a houseplant’s needs is by checking the soil moisture. Experts recommend the finger test: pushing an index finger about one to two inches deep into the soil. If the soil feels damp or cool at that depth, watering should be postponed until the soil feels completely dry. Small pots can also be checked by lifting them, as a dry pot will feel significantly lighter than a wet one.
When it is time to water, the temperature of the water matters greatly to the root system. Using frigid water straight from the tap can shock the roots, potentially causing the plant to drop leaves or wilt. Use room-temperature or tepid water, which can be achieved by filling the watering can and allowing it to sit for a few hours before application. While soil watering decreases, the dry indoor air requires attention to humidity, which can be increased by placing plants on pebble trays filled with water or by grouping plants together.
Watering Outdoor Plants and Dormancy
Outdoor plants exhibit two distinct behaviors in winter, which dictates their water requirements. Deciduous plants, such as trees that shed their leaves, enter true dormancy, minimizing water loss. These plants need minimal winter water, mainly to prevent the roots from drying out (desiccation). Supplemental watering for dormant plants is only necessary during long, dry periods.
Evergreen plants, including conifers and broadleaf varieties, continue to transpire and photosynthesize throughout the winter, albeit at a reduced rate. Because they retain foliage, they are actively losing moisture and are susceptible to winter desiccation. Broadleaf evergreens, such as rhododendrons and boxwoods, are particularly vulnerable and may require consistent supplemental watering during dry spells.
The timing and technique of outdoor winter watering are important for moisture utilization. Water should only be applied when the air temperature is above 40°F (4°C) and the ground is not frozen. If the soil is frozen solid, water cannot penetrate the roots and may freeze on the surface. When watering, a slow, deep soaking is the most effective method, encouraging moisture to reach the entire root zone. Applying a thick layer of mulch around the base of plants helps by insulating the soil and retaining moisture, protecting the roots from deep freezing.
Recognizing and Preventing Winter Watering Mistakes
The greatest threat to a plant during the winter is overwatering, exacerbated by the slow-drying nature of cold soil. Overwatered soil lacks oxygen, leading to root suffocation and the onset of root rot. Signs of overwatering include a general yellowing of the leaves, especially newer growth, or a wilting appearance even when the soil is visibly wet. Other indicators can be a foul odor emanating from the soil or the presence of fungus gnats, which thrive in damp conditions.
Conversely, underwatering can manifest as brown, crispy leaf edges or tips, and the soil may pull away from the sides of the pot. While both over- and underwatering can cause similar wilting symptoms, an underwatered plant’s leaves feel dry and brittle, unlike the soft, mushy texture of an overwatered one. Prevention centers on ensuring excellent drainage, meaning never allowing the pot to sit in standing water after soaking. Suspend the use of fertilizer entirely throughout the winter season because plants are not actively growing.