Snow Is Protection: Understanding Winter Survival in the Garden

Will weeks of sub-zero cold damage hydrangeas, berries, and other garden plants? Understanding winter survival in garden plants is more complicated than temperature alone.

How Winter Survival Works in Garden Plants

After a stretch of extreme winter weather — nights dropping below 0°F and days stuck in the teens and twenties for weeks, combined with snow cover and even a layer of ice — many gardeners assume their landscape has been severely damaged.

Surprisingly, that kind of winter is often less destructive than a mild one.

In cold climates, plants are adapted to low temperatures. What they are not adapted to is instability. The real danger is fluctuation — warming, thawing, refreezing, and exposure — not steady cold.

To understand what actually happened in your garden, we need to start with the role snow plays.

Snow Is Not the Enemy — It Is Insulation

A continuous snow layer acts like a natural blanket over the soil. Each inch provides insulation (R3- R5 per inch), preventing soil temperatures from following air temperatures downward. Snow plays a major role in winter survival for garden plants because it insulates soil from extreme air temperatures.

Even when air temperatures dropped below 0°F, soil under snow typically remained in the upper 20s. That is well within the survival range of hardy plant roots.

This means plants buried in snow were actually protected from:

• desiccating winter wind
• rapid temperature swings
• root freezing
• crown exposure

Ironically, the most injured plants after severe winters are usually the ones where snow melted off and refroze as ice, or where wind kept them exposed.

So if your garden stayed snow covered, most roots and crowns likely came through winter intact.

When snow and ice seal the ground, natural food sources disappear almost overnight — seeds are buried, insects are locked away, and birds burn enormous calories simply staying warm. This is exactly when feeders become lifesaving rather than decorative, so if you’re able, keep them filled and unfrozen (see my post Extreme Weather Strategies for Birds for what and how to feed safely).

Hydrangeas — What Survives and What Doesn’t

Hydrangeas respond differently depending on type.

Bigleaf (Mophead) and Mountain Hydrangeas (Hydrangea macrophylla & serrata)

These are the ones gardeners worry about most — and correctly so — but not because the plant dies.

When temperatures fall below about 5°F, the overwintering flower buds often freeze. However, the stems and root system usually survive, especially under snow.

In spring you may notice:
• healthy leaf growth
• strong stems
• very few or no flowers

This is not plant death — it is bud loss. The shrub will recover and bloom normally the following year. Prune back to healthy buds and live wood in the spring.

Reblooming Hydrangeas After a Harsh Winter

Reblooming bigleaf hydrangeas — such as Endless Summer®, BloomStruck®, and Let’s Dance® types — were bred to handle cold winters better than traditional mophead hydrangeas.

Unlike older varieties that bloom only from last year’s buds (old wood), rebloomers produce flowers from both:
• overwintered buds
• new spring growth

Because of this, extreme cold rarely prevents flowering entirely.

What You May See This Spring

After prolonged sub-zero temperatures:

• plants leaf out normally
• early summer flowers may be sparse or absent
• flowering begins later than usual
• blooms appear lower on the plant or on new stems

This is not plant damage — it is loss of overwintered buds.

Snow-covered stems often keep some buds alive, which is why flowers sometimes appear only near the base.

Spring Pruning Warning

Do not prune heavily when growth begins.

Early pruning removes surviving buds and delays blooming.

Instead:
• wait until fully leafed out
• remove only dead tips and hollow stems

What It Means:
A severe winter turns an early-flowering year into a late-flowering year — but reblooming hydrangeas almost always bloom.

Panicle and Smooth Hydrangeas (H. paniculata & arborescens)

These bloom on new wood. The cold winter has virtually no effect on flowering because buds are formed after growth begins in spring.

These types actually prefer a cold dormant period and typically perform beautifully after winters like this.

Blueberries — Built for Cold Dormancy

Blueberries are much hardier than most gardeners realize. Northern highbush blueberries tolerate temperatures between -20°F and -30°F once fully dormant.

Because this freeze occurred mid-winter, plants were acclimated and protected by snow cover. I always mulch my berries with bales of pine straw to insulate and acidify the ground.

Possible minor effects:
• tip dieback above the snow line
• slightly reduced fruit set if buds were unusually advanced before the freeze (unlikely)

But widespread plant loss is very rare under stable cold conditions. Roots and crowns should be perfectly healthy.

Raspberries and Blackberries — Cane vs. Crown Survival

Brambles depend on whether fruit forms on old or new canes.

Summer-bearing (floricane types)

The upper portions of canes exposed above snow may die back. The lower sections protected by snow almost always survive. Plants will grow and fruit, but yields may be smaller.

Fall-bearing (primocane types)

These fruit on new growth. Winter cold does not matter — they will regrow from the base and produce normally.

Snow cover is actually ideal protection for raspberries and blackberries. It is more important to keep the hungry deer from browsing on the canes in the winter when there isn’t much forage.

Perennials and Ornamentals — The Ice Problem

Most hardy perennials tolerate deep cold very well. The greater concern this winter was not temperature but oxygen deprivation.

Extended ice layers can seal the soil surface and suffocate crowns. When this happens, losses tend to occur in plants that dislike winter moisture:

• lavender
• rosemary
• gaura
• penstemon
• some heucheras
• fall-planted shrubs

If plants fail this spring, the cause will usually be winter wetness rather than freezing.

Camellias

I have a camellia that is looking very sad. Camellias have three different levels of hardiness:

So after a severe freeze, the shrub usually lives — but blooms are affected.

What you’ll likely see this spring

1. Bud drop

The most common result.

Buds look normal through winter, then:

• turn brown

• feel soft

• fall off without opening

The plant is fine — the flowers froze.

The Damage You See in Spring May Not Be From Winter

The most important point: winter injury often occurs after the coldest weather is over.

Late winter warm spells can trigger plants to wake from dormancy. When a hard freeze follows, newly active buds are killed. Gardeners often blame the earlier deep freeze, but the real culprit is the temperature swing.

For hydrangeas, fruit crops, and flowering shrubs, March and April determine the season far more than January.

What Gardeners Should Expect

After a long, stable cold period with snow cover:

Roots are usually safe
Plants are usually alive
Flower buds may be reduced
Exposed stems may die back
Moisture-sensitive plants may struggle

But widespread plant death is unlikely.

Paradoxically, consistent cold winters are often healthier for landscapes than erratic mild ones. Most winter survival problems in garden plants come from exposure and temperature swings, not steady cold.

In my next post, we’ll walk the garden together and talk about exactly what to look for when the snow finally melts — and why the first spring inspection matters more than any cleanup.

For a good explanation of how to protect plants during winter, go to Cornell’s article on Simple Ways to Prevent Winter Plant Injury.