Getting through winter can be tough on outdoor plants. Frigid temperatures, icy winds, and heavy snowfall conspire to damage even the hardiest of specimens. However, with some preparation and vigilance, you can help your outdoor plants survive and thrive despite winter’s freezing onslaught. This comprehensive guide will provide useful tips and techniques to protect your beloved outdoor plants from the cold.

Why Outdoor Plants Need Protection from Freezing

Outdoor plants are adapted to withstand seasonal variations in temperature and moisture. However, extremely frigid conditions can injure or kill many species not specifically bred for cold hardiness.

Freezing temperatures damage plants in the following ways:

• Dehydration – Most plants continue to lose moisture during the winter through transpiration and evaporation. If the ground is frozen, the plants cannot absorb new water through their roots. This lack of available water can desiccate and eventually kill the plant.
• Cell rupture – As water within plant cells freeze and expand, it can rupture cell walls and membranes. This damage is often visible as blackened, water-soaked lesions on stems, leaves, flowers, and fruits.
• Toxic ice formation – Extracellular ice crystals can concentrate solutes within the plant to toxic levels. This chemical imbalance disrupts metabolism.
• Lack of nutrients – Frozen soil prevents active uptake of important minerals. Nutrient deficiency weakens the plant over time.
• Vulnerability to pests and disease – Cold-injured plants are more susceptible to harmful infections.

How to Judge a Plant’s Cold Hardiness

When selecting outdoor plants, it is important to consider their USDA Plant Hardiness Zone. This gives you an idea of the lowest temperature a plant can withstand.

• Most gardening resources provide a plant’s hardiness zone information.
• Choose plants rated for your zone or lower.
• Microclimates may allow you to stretch the zones by a half zone. For example, if you’re in zone 5, some zone 5.5 plants may survive.
• Recently bred cultivars may be more cold tolerant than their species. Check tags and descriptions.

Other aspects that influence cold hardiness:

• Origin – Plants native to temperate regions are more likely to survive your winters. Tropical and subtropical plants are not.
• Plant age – Younger, established plants are less hardy than mature specimens. Avoid planting new acquisitions late in the growing season.
• Plant health – Vigorous, healthy plants better withstand stress. Weak, diseased plants are more susceptible to cold damage.
• Previous exposure – Plants that have been hardened off by gradual temperature changes tolerate cold better.
• Plant structure – Broadleaved evergreens are less hardy than needled and scaled types. Plants with thin bark are less tolerant than those with thick, corky bark.

How to Prepare Outdoor Plants for Winter

Proper care in fall can help ready your outdoor plants for freezing conditions.

Stop Fertilizing

• Fertilizer stimulates new growth, which is highly vulnerable to freezing.
• Cease fertilizing 6-8 weeks before your average first frost date.

Provide Extra Water

• Hydrate plants thoroughly in fall. Moist soil retains heat better than dry soil.
• Water during dry periods in winter when possible. Be careful — soggy soil can damage roots.

Mulch Well

• Apply 2-4 inches of shredded bark, compost, leaves, or other organic mulch around plants after the ground freezes.
• Mulch insulates roots and prevents frost heaving, which can push plants out of the ground.

Prune Judiciously

• Remove dead or damaged wood.
• Cut back lanky growth to reduce surface area and minimize storm damage.
• Wait to do major pruning until late winter/early spring when plants are dormant.

Weed and Clean Up

• Pull weeds, which may harbor pests.
• Rake fallen leaves, which can smother plants.
• Remove debris to prevent disease.

Consider Temporary Covers

• Burlap, garden fleece, pine boughs, etc. can add insulation around vulnerable plants.
• Make sure covers do not crush or abrade foliage and allow airflow to prevent rot.
• Erect plastic tunnels over beds of semi-hardy perennials.

Plant Windbreaks

• Stake and tie trees/shrubs to prevent rocking, which can damage roots.
• Build a simple wooden frame around delicate plants.
• Site new specimens on the lee side of walls or established plantings.

How to Protect Container Plants from Freezing

Plants growing in containers are more exposed and thus more prone to cold damage.

Choose an Appropriate Pot

• Unglazed terra cotta and concrete pots retain more heat than metal, wood, or plastic.
• Dark colors also absorb heat better.
• Make sure pots are large enough — roots need adequate room to grow. Upgrade pot size as needed.

Use Insulating Materials

• Pack bark chips, compost, sawdust, or foam peanuts around the pot to provide a buffer.
• Bubble wrap makes an excellent insulator — secure it around the container.
• Place pots in large decorative baskets or plastic nursery trays.

Provide Shelter

• Move containers against the foundation or southern exposure of your home. The radiant heat will provide warmth.
• Construct temporary cold frames around your pots using old windows and lumber.
• Store delicate plants in an unheated garage, shed, or basement during extreme cold. Check them periodically for water needs.

Consider Temporary Covers

• Drape flexible row cover material over your containers and secure the bottoms with rocks or staples.
• Make mini hoop houses using flexible conduit or PVC pipes and plastic sheeting.

Maintain Moisture

• Keep soil slightly moist but not soggy during winter. Poke your finger into the soil to check moisture level.
• Consider lining pots with plastic to maintain humidity and reduce evaporation.
• Place gravel trays filled with water under each pot to create a humid microclimate.

How to Protect Perennials from Freezing

Perennials form the backbone of many gardens. Protect your investment in these long-lived plants with proper winter care.

Mulch Thoroughly

• Spread 2-4 inches of shredded leaves, pine straw, compost, or bark around plants after the ground freezes.
• Mulching prevents rapid temperature fluctuations that can damage roots.

Cut Back Dead Foliage

• Leave healthy stems and leaves intact for insulation.
• Trim off limp, discolored foliage, which can harbor disease.

Cover with Row Covers

• Drape breathable row cover fabric over plants and secure the edges with rocks, staples, or U-pins.
• Remove covers in spring after danger of hard frost has passed.

Insulate with Leaves

• Stuff dry leaves between upright dormant perennials and lightly cover beds with additional leaves.
• Leaves prevent soil temperature changes and drying winds.

Plant in Sheltered Areas

• Site new plantings on the south side of walls, hedges, or evergreen trees.
• Avoid planting in frost pockets or dips where cold air pools.

Wait to Cut Back

• Leave expired ornamental grasses and perennial seed heads stand for winter interest and insulation.
• Delay cutting back until early spring to protect crown buds from damage.

Mark with Stakes

• Identify the location of dormant plants with tall stakes.
• Prevent accidentally digging into hidden root zones.

Select Cold Hardy Varieties

• Choose perennial types rated for colder zones than your climate. Some good choices are irises, sedums, daylilies, and ornamental grasses.
• Research species within a genus – some are hardier than others.

How to Protect Shrubs from Freezing

Broadleaf evergreen shrubs often suffer dieback and browning after severe winters. Proper care can help minimize this damage.

Provide Wind Protection

• Build burlap screens between susceptible shrubs to block drying winds, which intensify winter desiccation.
• Plant specimen shrubs on the leeward side of walls, fences, or other plantings.

Insulate with Mulch

• Apply a 2-4 inch layer of bark chips, pine straw, or chopped leaves after the ground freezes.
• Keep mulch off direct contact with stems to prevent rotting.

Wrap Shrubs

• Loosely wrap chicken wire around the perimeter of shrub branches, then stuff leaves between the branches and wire.
• Bind flexible cardboard around the leaves to secure them in place.

Maintain Moisture

• Water deeply before major frosts and during winter thaws or dry periods.
• Avoid overwatering – soggy soil can damage roots during freezing weather.

Whitewash Trunks

• Paint thin trunks with white latex paint diluted with water to reflect sunlight and prevent sunscald.
• Avoid overpainting – the bark still needs airflow.

Delay Major Pruning

• Put off reshaping, renewal pruning, and major trimming until late winter when you can assess damage.
• Remove only broken branches and tattered foliage in fall.

Choose Cold Hardy Varieties

• Select species rated below your zone such as yaupon holly, inkberry holly, boxwood, and rosemary.
• Research specific cultivars – some are more winter hardy than others.

How to Protect Trees from Freezing

Mature trees can endure quite cold conditions. However, some extra care will help prevent long-term damage.

Prevent Rocking

• Check tree trunks and stake any loose specimens to prevent rocking, which tears vital roots.
• Remove stakes in spring once the ground thaws.

Wrap Young Bark

• Wrap the thin bark on young trees with commercial tree wrap or burlap strips to prevent cracking.
• Avoid overwrapping – leave the top foot and bottom six inches exposed.

Insulate Tree Base

• Mulch around the base of trees with 2-4 inches of bark chips or chopped leaves to insulate the roots.
• Keep mulch 6 inches away from the trunk to prevent rotting and rodent issues.

Whitewash Trunks

• Protect thin-barked trees from sunscald by painting lower trunks with diluted white latex paint.
• Allow the top foot and lower six inches to remain unpainted for airflow.

Provide Wind Protection

• Drive stakes around young trees and wrap burlap strips between the stakes to reduce wind whipping.
• Situate new plantings on the leeward side of existing windbreaks.

Maintain Moisture

• Water deeply when winter rains are insufficient to replenish soil moisture.
• Aim for moist but not saturated soil to prevent root damage.

Prune in Early Summer

• Avoid pruning deciduous trees during fall and winter. this stimulates tender new growth prone to dieback.
• Stick to late spring/early summer pruning to minimize cold injury.

Select Hardy Species

• Choose hardy types such as maple, oak, honeylocust, screwpine, fruitless pear, and American hornbeam.
• Avoid marginally hardy trees like citrus, crape myrtle, palms, and bananas.

How to Protect Frost-Sensitive Annuals from Freezing

Many popular warm-season annual flowers shrivel at the slightest touch of frost. Give tender annuals a fighting chance by taking these preventative measures.

Provide Row Covers

• Cover plants with breathable row cover fabric once nighttime temperatures drop to 45° F.
• Secure the edges with boards, rocks, landscape pins, or wire hoops.

Water Well Before Frosts

• Moist soil retains more heat than dry soil. Deep water in late afternoon before overnight freezes are predicted.
• Just take care not to oversaturate the soil, which can damage roots.

Use Containers Strategically

• Move small pots against warm walls or inside cold frames, a greenhouse, or covered porch.
• Group together for insulation or bury in mulch.

Choose Protected Sites

• Plant frost-tender annuals along the foundations or in the shelter of hedges, fences, or stone walls.
• Avoid frost pockets and low-lying areas of the landscape.

Apply Light Mulches

• Cover soil around plants with a couple inches of pine straw, chopped leaves, or compost to insulate roots.
• Take care not to bury foliage – mulch should remain below the leaves.

Delay Planting

• Don’t rush to plant warm-season annuals in spring. Wait 2-3 weeks after your average last frost date.
• Be ready to protect new plantings in the event of a late cold snap.

Remove Spent Plants Promptly

• Once pretty annuals are hit by hard frost, pull them up and discard debris to prevent diseases.
• Make room for cold-tolerant fall plantings.

Select Frost Hardy Varieties

• Certain types, like pansies, flowering kale and cabbage, and snapdragons, endure light frosts.
• Substitute these for more tender species.

How to Protect Tropical Plants from Freezing

Tropical plants like bananas, palms, and elephant ears need special measures to survive winters beyond their comfort zone.

Grow in Containers

• Containerize plants to simplify overwintering indoors. Repot to fit.
• Dwarf varieties better adapt to indoor environments.

Protect with Row Covers

• In zones 8-9, drape breathable row cover over plants when frost threatens. Some tolerate brief light freezes.
• Remove covers daily to prevent overheating.

Provide a Heat Source

• Place pots atop electric heating mats set at 50°-60°F to keep roots from freezing.
• A miniature greenhouse with a small portable heater can shelter marginally hardy specimens in the ground.

Insulate with Mulch

• Mound a 8-10 inch layer of bark chips, leaves, straw or other dry material around the base of plants to protect roots and crown.

Bring Indoors or Undercover

• Move containers to an enclosed porch, greenhouse, basement, or heated garage once overnight lows drop below 45°F.
• Keep plants dry with minimal watering. Slowed growth prevents etiolation.

Cut Back Before Bringing In

• Prune back foliage by 1/3 to 1/2 before moving inside. Less leaf mass reduces water needs.
• Direct growth isn’t necessary. Focus resources on dormancy.

Gradually Reacclimate in Spring

• Set plants outside on warm days and bring back in at night until danger of frost passes.
• Slowly reintroduce to direct sun over two weeks to avoid leaf burn.

Select Cold Hardy Species

• Some tropical look-alikes tolerate colder winters, like cannas, elephant ears, and butterfly gingers.
• Research specific varieties – some are more winter hardy than others.

Common Freezing Injury and Prevention Tips

Here is a quick rundown of symptoms of cold damage and how to help plants avoid it:

Wilting, drooping leaves

• Cause – Lack of water uptake through frozen soil
• Prevention – Water well before frost, mulch roots

Brown, watersoaked stems/foliage

• Cause – Ice crystal damage to cell structure
• Prevention – Insulate plants, maintain moisture

Blackened leaves and flowers

• Cause – Tissue death from hard freeze
• Prevention – Cover susceptible plants overnight

Sunken, shriveled buds

• Cause – Dehydration from winds or frozen soil
• Prevention – Wrapping, windbreaks, mulching

Bark splitting

• Cause – Fluctuating temperatures, winter sun
• Prevention – Tree wraps, trunk paints, pruning paint

Fallen leaves/needles

• Cause – Desiccation
• Prevention – Shelter plants, maintain even moisture

Death of roots or crown

• Cause – Extreme cold, frost heaving
• Prevention – Mulch, eliminate air pockets around roots

Delayed spring growth

• Cause – Damage to root system over winter
• Prevention – Insulate roots, prevent heaving

Conclusion

Getting plants safely through winter is possible with proper care and protection from freezing temperatures and drying winds. The keys are insulating sensitive plants, maintaining moisture to non-frozen levels, preventing desiccation, and selecting specimens within your climate’s hardiness range. Mulching and watering before anticipated frosts, moving containers in/under cover, and wrapping or blanketing plants to block wind are extremely beneficial. With attention to good cultural practices in fall and vigilant care when freezing weather hits, you can protect your outdoor plants from the ravages of winter. They will reward you with vigorous growth and beauty when milder conditions return.

Frequently Asked Questions (FAQs)

Here are some common questions and answers about protecting outdoor plants from freezing:

Q: Is it okay to prune trees and shrubs in fall to prepare them for winter?

A: It’s best to avoid heavy pruning in fall and early winter since this can stimulate new growth that is easily damaged by cold. Limit fall pruning to removing dead or damaged branches. Save any major corrective pruning for late winter/early spring when plants are still dormant.

Q: Should I fertilize outdoor plants in fall?

A: No, fertilizing encourages tender new growth that is vulnerable to freezing damage. Stop fertilizing 6-8 weeks before your first expected frost.

Q: Do outdoor plants need more or less watering in winter