Understanding How Roses Prepare for Winter

Most of us tend to “baby” our roses—especially as winter approaches. But long before we begin mounding, mulching, or fussing with protection, our roses are already hard at work preparing themselves for the cold season. This article isn’t about what you should do—it’s about what your roses are doing naturally, and how understanding those processes can help you provide the right support at the right time.

A Little Plant Biology

During the growing season, rose leaves are photosynthesis powerhouses, turning water and carbon dioxide into carbohydrates. These carbohydrates become the plant’s energy currency, supporting everything from new shoots and flowers to root growth.

A network of vascular tubes moves these diluted sugars throughout the plant. Along the way, roses also manufacture hormones such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid. These hormones are the traffic directors of growth—some stimulate activity, others slow it down. As environmental cues shift, hormone levels shift too, guiding the plant into dormancy.

What Happens in Fall

As days shorten and temperatures drop, roses receive strong signals to slow down. Less nitrogen, less water, and longer nights all encourage the plant to begin producing more abscisic acid, a hormone that inhibits growth and helps close the stomata—tiny pores on the leaf surface. This reduces water loss and helps the plant begin its transition to dormancy.

At the same time, carbohydrates are no longer needed for rapid growth. Instead, they begin to migrate from the leaves into the canes, where they are stored as sugars. These sugars will become essential winter “antifreeze.”

Hormones such as ethylene and abscisic acid also trigger leaf drop. Specialized cells at the base of each leaf dissolve, allowing the leaf to detach while sealing off the cane. (The same process causes petals to fall—and yes, storing roses near apples, which release ethylene, will hasten petal drop!)

How Roses Survive Freezing Temperatures

If a rose were to freeze suddenly without preparation, water inside its cells would expand and rupture them. Dormant plants avoid this through an extraordinary adaptation:

  1. The outer cane surface freezes first.

  2. Water between cells freezes next. As this occurs, water inside the cells is drawn outward.

  3. Sugars inside the cell remain, becoming more concentrated and lowering the freezing point—much like antifreeze.

If temperatures rise briefly during winter, the danger comes when intercellular ice melts and re-enters the cells. If a sudden hard freeze follows, the now-diluted cell contents can form damaging ice crystals. This is why rapid freeze–thaw cycles—more than cold itself—cause the greatest winter injury.

Winter Protection: What It Actually Does

Contrary to popular belief, winter protection is not meant to keep a rose warm. Instead, its purpose is to slow down the freezing and thawing cycle. Mulch or mounding stabilizes temperatures around the crown and moves freeze–thaw activity to the mulch surface rather than the roots.

Frozen soil itself isn’t harmful; it’s heaving—caused by expanding surface ice—that snaps roots. Mulch prevents this by buffering the soil surface.

Special Considerations for Container Roses

Roses in pots face greater risk because their roots do not experience the moderating effect of surrounding earth. Roots are less cold-hardy than canes. While many roses survive occasional dips into the low 20s in an unheated space, extended temperatures around 15°F or lower can cause significant root loss in small containers.

When Summer Stress Affects Winter Hardiness

Roses that suffered from drought, defoliation, or pests in late summer have not stored adequate carbohydrates for winter. Their canes contain fewer dissolved sugars, reducing their natural antifreeze and increasing the risk of winter injury.

Such roses should receive winter protection soon after the first hard frosts—and a bit of gardener’s prayer certainly never hurts.

A Practical Approach to Winter Prep

For healthy, vigorous roses:

  • Allow them to go dormant naturally.

  • Let leaves drop on their own, helping only when necessary.

  • Add winter protection when sustained temperatures are expected below ~20°F.

  • Protect crowns and exposed canes, especially in windy areas.

  • Roses on their own roots often require less protection.

Most importantly—trust that roses have evolved remarkable mechanisms to care for themselves. Our role is simply to support those natural processes.