Caring For Outdoor Plants In Winter

Winter may look like a quiet season in the garden, but outdoor plants are still responding to changing soil moisture, temperature, wind, sunlight, and periods of freezing and thawing. Many perennials, trees, and shrubs enter dormancy, while evergreens continue to lose moisture through their foliage even when growth has slowed.

The most important part of winter plant care is understanding what is normal for each plant. A dormant perennial may disappear completely until spring, while an evergreen should retain its foliage. Knowing the difference can keep you from watering, pruning, or protecting a plant unnecessarily.

Understand Winter Dormancy

Many cold-hardy perennials, trees, and shrubs naturally slow or stop visible growth as temperatures fall and days become shorter. This period of dormancy helps plants survive winter and prepare for the next growing season.

Herbaceous perennials may lose all of their above-ground growth even though the roots and crown remain alive below the soil. Deciduous trees and shrubs lose their leaves, while evergreens retain foliage but grow very little during cold weather.

A plant that looks lifeless in January is not necessarily dead. Avoid digging up dormant plants or assuming they have failed simply because there is no visible growth.

Start With Plants Hardy For Your Area

Plants that are appropriately hardy for your USDA Plant Hardiness Zone generally require much less intervention during winter than plants growing near or beyond the cold edge of their recommended range.

Hardiness zones are based on average annual extreme minimum winter temperatures. They are a useful starting point, but snow cover, wind exposure, drainage, microclimates, and sudden temperature changes can also influence how well a plant survives winter.

Watch Winter Soil And Drainage

Good drainage matters throughout the year, but winter creates additional challenges. Waterlogged soil has very little air available to plant roots, and repeated freezing and thawing can move poorly rooted plants upward in the soil.

This movement is known as frost heaving and is most common with shallow-rooted or recently planted perennials when soil repeatedly freezes and thaws.

If you notice a small perennial crown being pushed upward during winter or early spring, gently settle it back into place when the soil is workable and cover exposed roots with soil.

Avoid creating permanently wet conditions in an attempt to protect plants from cold. Most garden plants still require oxygen around their roots and should not remain in saturated soil for long periods.

Maintain Mulch Around The Root Zone

Mulch helps reduce rapid fluctuations in soil temperature, conserve moisture, and protect roots from repeated freezing and thawing.

Around established trees and shrubs, maintain approximately 2 to 3 inches of organic mulch over the root zone. Keep mulch away from trunks and woody stems rather than piling it directly against them.

Tender perennials or newly planted material may benefit from additional winter protection depending on the climate and plant.

Protect Evergreens From Winter Drying

Evergreen plants can lose moisture through their foliage throughout winter. When the soil is frozen, roots may not be able to replace that moisture, which can result in browning known as winter burn or winter desiccation.

Newly planted evergreens and plants growing in exposed, windy locations are especially vulnerable. Bright winter sun and reflected heat from buildings can increase moisture loss as well.

Windbreaks or burlap screens can help protect susceptible plants. In many cases, it is better to create a screen around the exposed sides of the plant rather than tightly wrapping the foliage.

Do Outdoor Plants Need Water In Winter?

Sometimes. Winter watering needs depend heavily on climate, rainfall, snow cover, soil conditions, and the type of plant.

In cold climates, do not attempt to water frozen soil. However, extended winter drought can damage roots and evergreens when there is little snow or precipitation.

Colorado State University Extension recommends supplemental winter watering during prolonged dry periods when air and soil temperatures are above approximately 40°F and there is no snow cover.

Newly planted trees and shrubs, evergreens, shallow-rooted woody plants, and plants growing in windy or south- and west-facing locations may require the closest attention during dry winters.

In warmer climates where plants remain actively growing, continue checking soil moisture normally and adjust watering to the plant's needs rather than stopping simply because it is winter.

Should You Prune Plants During Winter?

Winter can be a good pruning season for some trees and shrubs, but pruning timing depends on the plant.

Many deciduous trees and summer-flowering shrubs can be pruned during late winter while they are dormant. Plants such as panicle hydrangea, smooth hydrangea, and butterfly bush generally bloom on new growth and can often be pruned before spring growth begins.

Spring-flowering shrubs are different. Forsythia, lilac, azalea, spring-flowering spirea, and many viburnums produce flowers on older stems. Pruning them during winter can remove flower buds that were formed the previous season.

These shrubs are generally pruned shortly after they finish flowering instead.

What About Cutting Back Perennials?

Herbaceous perennials can often be cut back after the top growth has died completely, but there is usually no need to rush.

Leaving healthy stems and seed heads standing through winter can provide visual interest, trap insulating snow around plant crowns, and provide food or shelter for wildlife.

Diseased foliage is more useful to remove because it may harbor pathogens that can affect plants the following season.

Winter Care For Plants In Pots

A plant growing in a container experiences winter differently from the same plant growing in the ground. Roots in pots are surrounded by a relatively thin layer of soil and are exposed to much greater temperature fluctuations.

A perennial or shrub that is perfectly hardy in the ground may not be equally hardy in an exposed container.

Options For Overwintering Containers

• Move the container to a protected location. A sheltered garage, shed, or similar space can reduce temperature extremes for dormant plants.
• Group containers together. Placing pots close together in a protected area can reduce exposure to wind and extreme temperatures.
• Plant the perennial in the ground. If conditions and timing allow, moving a hardy perennial from its pot into the landscape can give the roots more insulation.
• Insulate the container. Large containers may sometimes be protected with mulch or insulating materials around the outside of the pot.
• Bring tropical plants indoors. Plants that do not require winter dormancy can sometimes be grown as houseplants.

Always consider the particular plant. A hardy dormant shrub and a tropical hibiscus need very different winter environments.

Protect The Container Too

Freezing moisture can crack some ceramic, terra-cotta, and other porous containers. If the container itself is not rated for freezing conditions, move it somewhere protected before prolonged freezing weather arrives.

Regardless of material, make sure outdoor containers have adequate drainage so water does not remain trapped around plant roots.

Should Outdoor Plants Be Brought Inside?

Not necessarily. Many cold-hardy perennials and shrubs need a natural dormant period and are better overwintered in a protected cold location than inside a heated home.

A hardy plant such as catmint, hosta, or many flowering shrubs generally does not become a houseplant simply because it is growing in a container.

Tropical plants and true houseplants that spent summer outdoors are different. These plants should usually return indoors before temperatures fall below their tolerance.

Inspect any plant carefully for insects or disease before bringing it inside, and keep returning plants away from established houseplants temporarily when possible.

Is Snow Good For Garden Plants?

In many cases, yes. A consistent layer of snow acts as insulation and helps protect soil and roots from rapid temperature fluctuations.

Problems are more likely when heavy wet snow or ice bends and breaks branches. If loose snow accumulates heavily on an evergreen, gently brush it upward and off the branches when practical rather than pulling branches downward.

Avoid striking frozen branches because cold wood can be brittle and easily damaged.

Protect Plants From Road Salt And Deicing Products

Plants near streets, driveways, and sidewalks may be exposed to salt spray or salty runoff during winter.

Whenever possible, avoid piling salt-contaminated snow around trees, shrubs, and perennial beds. Physical barriers can reduce spray along heavily treated roads, and using deicing products carefully around landscape beds can limit unnecessary salt exposure.

Wait Before Declaring Winter-Damaged Plants Dead

Winter damage is not always obvious immediately. Brown evergreen foliage, dead-looking stems, or delayed spring growth can make a plant look worse than it actually is.

In many cases, waiting until normal spring growth begins makes it easier to distinguish dead wood from living tissue.

For woody plants, a simple scratch test can help determine whether a questionable stem is still alive.

Winter Plant Care Checklist

Most Hardy Plants Need Less Winter Care Than You Think

Once a cold-hardy plant is established in the right location, winter care is often more about avoiding problems than constantly intervening.

Keep the root zone protected, monitor moisture during unusually dry weather, avoid unnecessary pruning, protect vulnerable containers and evergreens, and allow dormant plants to rest.

Knowing what is normal for each plant is the most important part. In many cases, the best thing you can do during winter is simply give your garden time and let the plants follow their natural seasonal cycle.